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Influence of dry micro abrasive blasting on the physical and mechanical characteristics of hybrid PVD-AlTiN coated tools
Journal of Manufacturing Processes 37 (2019) 446–456
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Influence of dry micro abrasive blasting on the physical and mechanical characteristics of hybrid PVD-AlTiN coated tools
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Abhishek Singh, S. Ghosh , S. Aravindan Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi Hauz Khas, Delhi, 110016, India
A R T I C LE I N FO
A B S T R A C T
Keywords: Micro abrasive blasting HiPIMS Morphology Superficial Hardness
The current study investigates the effect of the micro abrasive blasting (MAB) on the physical and mechanical characteristics of the cutting tools before and after coating deposition. Cutting tools were subjected to micro blasting by alumina (Al2O3) grains at varying pressure so as to improve the efficacy of the coating process. AlTiN coating of thickness 1.45 μm was deposited onto the tool surface by arc enhanced high power impulse magnetron sputtering (HiPIMS) hybrid deposition technique. The coatings were characterized using nano indentation, atomic force microscopy and micro scratch test. The results of nano indentations on the coated surface revealed the influence of the micro abrasive blasting technique and pressure on the superficial hardness. Surface morphology results showed better-adhered surface in case of cutting tools subjected to micro abrasive blasting before the deposition due to an increase in density of the nucleation sites for growth of aluminum which can be judged with the help of higher aluminum content in the energy dispersive x-ray analysis. The film adhesion of the coating onto the tool substrate is observed to be improved significantly with an increase in blasting pressure in the case of the samples subjected to micro abrasive blasting before coating. Additionally, X-ray diffraction analysis was performed to investigate crystallographic phases. The attained results provide insight concerning the optimum selection of micro abrasive blasting technique along with the pressure, for enhancing the cutting performance of coated tools during the machining of nickel-based superalloy Nimonic C 263.
1. Introduction Tribology at the chip-tool interface is one of the most important factors while cutting difficult to machine materials. Hence, tool surface properties and cutting environments (cooling and lubrication) have become major factors in controlling the machinability of these materials. Due to potential environmental hazards and high recycling cost of cutting fluids, industries prefer dry cutting processes. Coated tools offer a solution in terms of economic and eco-friendly machining. Improved mechanical and tribological properties of the coating are required to carry out dry or near dry machining at higher speeds. Hard coatings over cutting tools have been studied in recent past due to its greater wear resistance, oxidation resistance, high hardness and high-temperature operational capabilities[1–5]. Amongst them, physical vapor deposition (PVD) is one of the most widely used coating methods for industrial application over chemical vapor deposition. But the coating deposition by conventional techniques such as magnetron sputtering, and cathodic arc evaporation brings out various drawbacks. Magnetron sputtering results in low ionization while cathodic arc evaporation results in droplet formation (cause of poor adhesion between the
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substrate and coating material)[6–8]. The introduction of the high power impulse magnetron sputtering (HiPIMS) in 1999 by Schneider et al. [9] eliminated most of the drawbacks of these conventional PVD techniques by achieving coatings with improved coating structure, enhanced adhesion over the substrate and proper control over other deposition parameters[10,11]. But low deposition rates still remain a problem for the utilization of this technique in commercial applications. [12]. In order, to overcome these limitations a novel hybrid deposition technique has been developed that combines high power impulse magnetron sputtering (HiPIMS) with arc evaporation technique. This utilizes the benefits of both the techniques and promotes the formation of a high-density coating structure with improved friction characteristics. This process enables more direct control over the deposition process. It utilizes pulses of high power density in the range of few kW/ cm2 and low duty cycles (< 10%) resulting in improved ionization and higher deposition rates. Some studies have been carried out utilizing HiPIMS coating deposition technique and it has been found that there has been an improvement in the mechanical properties of the coating structure. Zhou et al.[13] reported that hybrid HiPIMS/DC magnetron sputtering
Corresponding author. E-mail address: [email protected] (S. Ghosh).
https://doi.org/10.1016/j.jmapro.2018.11.024 Received 26 July 2018; Received in revised form 22 November 2018; Accepted 24 November 2018 1526-6125/ © 2018 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.
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behaviour of these coatings is still unknown.
resulted in proper control over the deposition parameters as coating thickness, bias voltage, pulse rate, transition sharpness etc. Nowadays, various types of coatings are commercially used over the cutting tools due to their improved performance during the modern machining processes such as high speed, dry environments, heavy cutting loads, and difficult-to-machine materials. Though their sustainability over the cutting tools become pivotal when working at elevated temperatures. Therefore, in order to enhance the physical and mechanical properties of the coated tools various surface treatment techniques such as laser treatment, mechanical polishing, mechanical treatment, heat treatment etc. are employed[14,15]. Out of all the mentioned processes, micro abrasive blasting is gaining popularity due to low processing cost, improved coating performance and no heat affected zone formation (as in the case of laser texturing). The technique has been utilized both as a substrate treatment (known as pre-treatment) as well as a post coating treatment (called as post-treatment) to improve the adhesion between coating and substrate, film hardness, friction characteristics and fatigue life. The effect of micro blasting on various physical and mechanical characteristics have been reported by various researchers but are contradictory in nature[16–18]. Abia et al. [18] observed that the pre-treatment of the tool using glass microspheres for 30 seconds caused changes in the geometry of the cutting edges which in turn affected the efficiency of the coating deposition. The cutting edges of these samples show more roundness as compared to the untreated sample. Denkena et al. [19] analyzed that the changes in the geometry of cutting edges were caused due to the pressure exerted by the impingement of the abrasive particles. The radius of the cutting edge should be controlled for achieving good adhesion strength and reduced residual stress. Tonshoff et al.[20] have reported that the micro abrasive blasting of the carbide substrate before application of coating leads to increased adhesion properties between the coating material and the substrate. This is mainly due to an increase in the nucleation sites during deposition. Similar observation during the deposition of diamond films on the WC substrate was made by other researchers[21]. Other researches focussed on different aspects of micro abrasive blasting, but no detailed study has been done for understanding the efficacy of the process. Bouzakis et al.[16]reported that accumulation of high value of the residual stress at the cutting edge may cause detachment of the coating which in turn reduces the performance of coated tool during machining. Abia et al. [18] have revealed that pre-treatment of the substrate by glass microspheres has increased the surface roughness value of the substrate surface due to the impact of the microspheres resulting in superficial micro-cracks in the substrate. The pre-treated samples exhibited the presence of radial fissures and this corresponds to poor adhesion. Post coating treatment causes changes in characteristics such as cutting-edge geometry, composition, hardness and crystallographic phases. Bouzakis et al. [22] reported that micro abrasive blasting using Al2O3 grains induces stresses in the substrate of TiAlN coating which deteriorates the film ductility thus increasing its brittleness and hardness. In another study, Kennedy et al. [23] observed that the use of post coating treatment could be beneficial in terms of improving the cuttingedge strength however; this behaviour is limited to a specific blasting pressure. Micro abrasive blasting of the cutting tool can be useful in enhancing the fracture resistance of the coatings with proper control over the certain parameters[24]. From the available literature, it has been found that various studies are carried out to improve the performance of the cutting tools through micro abrasive blasting process, but no detailed study has been done for understanding the efficacy of the process. Therefore, appropriate experimental and analytical investigations were carried out in order to examine the effect of micro-blasting parameters on the coating properties. This work is to comprehend the effect of micro abrasive blasting as substrate treatment and coating treatment at varying pressure on the newly proposed hybrid technique as the metallurgical and mechanical
2. Experimental Details 2.1. Substrate treatment Micro abrasive blasting process involves the impingement of the wedge-shaped Al2O3 particles onto the substrate of the cutting tools for approximately 30 seconds. The used Al2O3 particles are of a size in the range of 10-20 μm. The distance between the blasting nozzle and the cutting inserts has been kept at 120 mm. The pre-treatment was carried out at three different pressure i.e. 0.1 MPa, 0.3 MPa and 0.5 MPa to analyze its effects at varying conditions. 2.2. Coating deposition AlTiN coatings were deposited on to the K grade cemented carbide inserts having CNMA 120408 geometry using Arc evaporation enhanced HIPIMS technique using AlTi targets which were fabricated by powder metallurgy route. All the substrates were chronologically cleaned in ultrasonic baths of acetone and alcohol for 4 minutes each, before being loaded into the vacuum chamber and were dried using pure nitrogen. The chamber was evacuated to a pressure of 5 × 10-3 Pa and the cutting inserts were heated up to a temperature of 420 °C before the coating deposition. Pre-sputtering of the target and plasma cleaning of the substrate was carried out in argon gas filled chamber with the aim of removing the impurities from the substrate and target surfaces. The deposition of 1.45 μm film of AlTiN took 51 minutes at a deposition temperature in the range of 420-450 °C. The thickness of the deposited coating was measured and verified using X-ray fluorescence technique. 2.3. Coating Treatment The coated samples were subjected to dry micro abrasive blasting process at two different pressures of 0.1 MPa and 0.2 MPa. The pressure values were so selected to understand the detrimental as well as benign effects of such post treatment. The process duration of the treatment was kept as 4 seconds. Al2O3 particles, used for the micro abrasive blasting, are having a size in the range of 10-20 μm and have wedgeshaped geometry. The distance between the blasting nozzle and the cutting inserts has been kept at 120 mm and is referred as the standoff distance (Fig. 1). In this study, the sample utilized for post-treatment doesn’t undergo any type of pre-treatment before coating deposition. 2.4. Coating Characterization Various experimental techniques were used for evaluating the physical, mechanical and tribological properties of the coated and uncoated specimens. X-ray diffraction technique was adopted to characterize the crystal structure of the as-coated, micro blasted/coated and coated/micro
Fig. 1. Micro abrasive blasting setup showing important parameters. 447
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From the microstructural analysis of the samples after coating deposition, it is found that the coating exhibits good adhesion on the pretreated substrates. This is correlated to the dense surface structure as well as fewer dislocations or defects. It can be also observed that no micro/macro holes or pores or droplet formation take place in hybrid deposited AlTiN coatings unlike the coatings deposited by conventional cathodic arc evaporation or magnetron sputtering technique (Fig. 3). On comparing the micrographs of the pre-treated/coated samples at the varying pressure no significant difference can be observed on the surface topography (Fig. 4). However, the effect of pressure can be better attributed to the enhanced adhesion of the coating, which is also later confirmed by performing adhesion tests and subsequent performance of the coated tools during the machining operation. The effect of the micro abrasive blasting can also be examined and correlated with the help of the EDS data which reveals that pre-treatment had caused an increase in the Al content from 32.118 % in asdeposited to 36.546 % in pre-treated sample (0.1 MPa) due to an increase in the density of the nucleation sites for growth of Al (Fig. 5).
blasted samples using Philips Panalytical X'pert, Cu Ka with a scanning speed of 1.0°/min, the step of 0.05°, and diffraction angles 2Ɵ between 20° and 80°. The surface roughness and topography of the samples were studied by means of atomic force microscopy (AFM, Make: Bruker Dimension icon with ScanAsyst) technique and Scanning Electron Microscopy technique respectively. The elastic modulus and hardness of the samples were evaluated using Hysitron Nano Indentor (TI 950 TriboIndentor) with loading and unloading time of 10 seconds and holding time of 2 seconds. 30 indents were taken at various localized sites for achieving the accuracy in measurement. The peak load (5000 μN) was selected in such a way that the effect or influence of surface roughness on the obtained results can be avoided whilst ensuring the nano-indentation depth to be 1/10th of the film thickness so that load-invariant coating hardness could be measured along with coating dominated elastic modulus. Micro scratch tests were performed so as to determine the friction and wear characteristics, microscopic deformation and micro-cracking behaviour of the coated samples through critical load analysis. The testing was performed at a ramp load of 1 N/min at peak load of 2 N. The adhesion of the samples was studied qualitatively by Rockwell HRC test using diamond indenter at a load of 1500 N.
3.2. Effect of MAB post-treatment on the coating morphology Post-treatment for the coated samples was carried out at two different pressures i.e. 0.1 MPa and 0.2 MPa. The surface morphology study reveals that the micro blasting of the coated surfaces results in an increase in the surface roughness of the coated samples due to the wedging action (Fig. 6). However, this effect is insignificant when the blasting pressure is 0.1 MPa.
2.5. Machining Performance Evaluation The cutting experiments were performed on CNC Leadwell T-6 turning centre for the nickel-based superalloy Nimonic C 263. Tool wear was measured at fixed values of cutting speed (60 m/min), feed (0.16 mm/rev) and depth of cut of 1 mm. The length of the cut was kept constant at 150 mm and each experiment was conducted two times for validating the obtained results. Flank wear of the worn surfaces was measured under an optical microscope (Zeiss AxioVisionSE64) while wear mechanism was studied using a scanning electron microscope. All the experiments were performed under dry condition.
3.3. Effect of MAB pre-treatment and post-treatment on the surface roughness of the coating The effect of microblasting on the substrate as well as coating can also be deduced by investigating another important aspect i.e. surface roughness. It is evident that micro abrasive blasting pre-treatment, as well as post-treatment causes a certain degree of roughening of the substrate and coating. The roughening is due to the impact of impinged abrasive particles. Uniform roughness is desirable over the substrate for achieving proper adhesion with the coated material. In the case of the coated films, surface roughness of optimum range is desirable. Takadoum and Bennani have observed that tool with higher surface roughness undergoes severe wear of coating. The tool with low surface roughness values may cause sticking with the tool-workpiece tribo-pair (increased contact area) resulting in higher tool wear thereby decreasing the tool life [28]. So the value of surface roughness should be in optimum range and are contained by a low coefficient of friction thus making chip flow easier. This fact reduces the tool wear thereby improving the tool life. The surface roughness measured using atomic force microscopy techniques shown in Fig. 7. The cutting tools were fabricated and manufactured using powder metallurgy and various other manufacturing processes to obtain the desired shape. The obtained surfaces are of varying roughness or have non-uniformity in their surface roughness values. These values are very low and hence certain surface modification technique needs to be adopted to obtain good adherence between the substrate and deposited film. The upper surfaces of the tools also have cobalt in a smeared (less contact area for mechanical interlocking) form which prevents good adhesion with the coated surface. The use of mechanical treatment technique i.e. micro abrasive blasting results in surface roughening of the substrate due to the impinged abrasive particles (Fig. 8). With the increase in the pressure for the impingement, the value of the surface roughness increases. When the pressure was 0.1 MPa, the value of surface roughness was found to be 80 nm which has increased to 209 nm at 0.5 MPa pressure. The increased roughness of the substrate is helpful in enhancing adhesion characteristics between the substrate and coating by promoting mechanical interlocking [29]. While comparing the surface
3. Results and Discussions 3.1. Effect of MAB pre-treatment on the substrate and coating morphology The surface morphology of the specimens was examined to understand the difference in the substrate conditions due to varying pressure. Micro abrasive blasting of the cutting tools causes variation in the surface topography. Cobalt present in the cemented carbide tools is more ductile in comparison to the tungsten carbide grains. During micro blasting, Co grains in the upper surface got depleted from the substrate (surface to be coated) resulting in the formation of new roughness peaks of the tungsten carbide grains of smaller heights. These peaks thus contribute to the substrate-coating adhesion enhancement due to mechanical anchoring. From Fig.2, it can be seen that the increase in blasting pressure results in an increase in the surface roughness of the samples as well as more exposure of the new carbide grains which may be helpful in improved adhesion between the substrate and coating[25]. It is noteworthy that the removal of the Co from the upper surface doesn’t affect its binding behaviour at the sub-surface layers of the cutting tool. However, the surface roughening observed on the tool substrate also depends upon the size of the abrasive which caused the material removal due to the impinging action of the wedge-shaped alumina. Hence the proper selection of the abrasive grain size is necessary. Micro blasting was carried out using fine grains as they lead to less deformation of the sub-surface layers. The abrasive effect of micro abrasive blasting with fine grain is also instrumental as it may lead to the constant stress level of the same degree as that of the ground surface [26]. The use of coarse grains results in more plastic deformation and leads to a high value of compressive stresses in comparison to the ground surface (uncoated tool without any surface treatment) which is not desired for the process [27]. 448
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Fig. 2. Substrate morphology at low and high magnifications showing surface roughening effect at varying pressure for the uncoated inserts.
Fig. 3. Scanning electron microscopy at low and high magnifications for the only coated samples in case of hybrid and conventional PVD technique.
Fig. 4. Scanning electron microscopy at low magnification for pre-treated/coated samples at varying pressure. Pre-treatment (0.1 MPa)/Coating Pre-treatment (0.3 MPa)/Coating Pre-treatment(0.5 MPa)/Coating
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Fig. 5. Energy dispersive x-ray spectroscopy for the as deposited and pre-treated(0.1 MPa)/coated sample.
roughness of the only coated samples and pre-treated/coated samples no significant difference in values was observed. Post-treatment of the coated films results in an increase in the values of the surface roughness. It is due to the impinging action of the wedgeshaped alumina particles. The surface roughness of samples reached a maximum of 170 nm in the case of coated and micro blasted sample (0.2 MPa). 3.4. Effect of MAB pre-treatment and post-treatment on the fracture toughness and hardness of the coated film The peak load is selected so that the indentation depth is less than 1/10th of the film thickness. Hardness of the samples has been measured and studied using nanoindentation tests at a peak load of 5000 μN. The hardness of the as deposited AlTiN film by the hybrid technique was 29.83 GPa which is much higher as compared to AlTiN films deposited by cathodic arc deposition technique[30]. The micro blasting of the substrate and the films induce compressive residual stresses which result in the variation in the hardness values. The results achieved through nanoindentation tests can be listed as
Fig. 7. Surface roughness values for cutting tools under various conditions.
ability of the coating to withstand high loads without undergoing fracture. So from the Table 1. It can be seen the post-treated samples exhibited higher plastic deformation resistance capability in comparison to the only coated samples. (b) The slight increase in the hardness of the pre-treated samples in comparison to the only coated may be due to the improved surface properties which occurred because of the uniformity in the stresses over the substrate during the coating deposition produced by the micro abrasive blasting. (c) Post-treatment of samples have resulted in good improvement of the superficial hardness which is due to the induced compressive stresses on the film. The change in the hardness also causes a diminution in the penetration depth during the nanoindentation. The increase in micro abrasive blasting pressure from 0.1 MPa to 0.2 MPa further increases the hardness value. (d) In order to clearly demonstrate the behaviour of the various samples the loading-unloading curves are shown in the Fig.9. It
(a) The value of H/E and H3/E2 presents the same variation trend as hardness in Table 1. These ratios reflect elastic strain to failure and plastic deformation resistance of the material. Thus taking into account the values of H, H/E and H3/E2 the samples subjected to post micro blasting (0.2 MPa) should exhibit strongest crack resistance while the only coated samples exhibit poorest again crack resistance. The high value of H/E can be beneficial as it provides a higher elastic strain to break and allow coatings to remain in the elastic limit during the loading conditions[31]. Beake and Ranganathan [32] have reported that the high H/E ratio is closely related to the tribological behaviour of the samples along with the hardness value. Similarly, H3/E2 ratio represents the ability of the coating to resist plastic deformation. Higher the value higher will be the
Fig. 6. Field emission scanning electron micrographs for coated/post-treated samples showing an increase in the surface roughening. 450
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Fig. 8. Surface roughening effect of the micro abrasive particles on the substrate (cemented carbide).
represents the variation in penetration depth with the applied load. The curves do not indicate any “pop in and pop out” which is an indicative of no crack formation over the coated surface. The hardness value in the case of coated and micro blasted (0.2 MPa) sample was maximum (34.89 GPa) while in the case of the only coated sample it is limited to 29.83 GPa. This increase in the hardness can also be correlated with the decrease in the penetration depth of the indenter or vice- versa.
3.5. Effect of MAB pre-treatment and post-treatment on the crystallographic phases and crystallite size coated films Fig. 9. Loading- unloading curves for only coated, pre and post treated samples.
X-Ray diffraction for the only coated and pre-treated and posttreated samples were carried out for determining whether any metallurgical changes such as phase transformation are taking place. The variation in the crystal structure or phase can be established primarily through shifts in the peak positions. During the analysis, the coating showed a cubic aluminum nitride (AlN) structure which is generally responsible for high hardness and wear resistance of the coating (Fig. 10). The XRD patterns of all the samples show the similar sequence of the peaks in terms of count. Hence it can be concluded that samples do not undergo any change in the phases due to micro abrasive blasting. The broadening of the peaks divulges the variation in the crystallite size [33]. Comparing the XRD spectra for the only coated and pre-treated samples, slight variation in the peak position was found on the higher degrees. This variation can be correlated to the released stresses due to micro abrasive blasting. The increase in the nucleation of the new grains due to micro abrasive blasting causes changes in the sub-surface morphology which in turn causes the densification of the coating structure which is confirmed by low-intensity peaks in case of micro blasted and coated samples (0.5 MPa) in comparison to only coated samples. However, at low pressure micro abrasive blasting, no such effect was observed and the value of the intensities remain the same. While comparing the post-treated sample spectra with the only deposited, the shifting of the peaks occurred on the lower angles (Fig. 11.) possibly due to the induced compressive stresses which cause dislocations as well as refinement of crystallites because of the impinging effect of the abrasive grains [34].
3.6. Effect of MAB pre-treatment and post-treatment on the adhesion of the coated films To evaluate the effect of micro abrasive blasting on the AlTiN films deposited by the hybrid technique, Rockwell HRC indentations tests were carried out on the film surface by making use of diamond indenter at a load of 1500 N. The diamond indenter penetrates the coated film inducing deformation plastically into the substrate and causing cracking, chipping and de-bonding of the coating. The Rockwell imprints were observed by scanning electron microscopy for qualitative analysis of the adhesion and are presented in Fig. 12. It can be observed that the coatings exhibited good adhesion for all of the samples with the generation of very few radial cracks (adhesion of class 1, EN-1071-8). It can be also observed that the microchipping occurred in case of only coated samples near the edges while this got significantly reduced in the case of the pretreated samples. Pre-treatment of the samples causes the surface roughening effect which improves the adhesion between the substrate and the coating. In the case of post-treated samples, an improvement in the adhesion can be seen. Post-treatment of the samples have resulted in radial cracks near the edges. These cracks are in micrometres in length and occur due to the indentation. The cracks gradually propagate within the columnar structure of the PVD coating, and then moves to the cobalt matrix of the WC-Co substrate [35]. The adhesion of the coating depends on different factors and hence
Table 1 Mechanical Properties of the samples under varying conditions. Sample
Hardness, H(GPa)
Elastic Modulus, E (GPa)
H/E
H3/E2 (GPa)
Only coated Pre-treatment(0.1 MPa)/Coating Pre-treatment(0.3 MPa)/Coating Pre-treatment(0.5 MPa)/Coating Coating/Post-treatment (0.1 MPa) Coating/Post-treatment (0.2 MPa)
29.83 29.97 30.46 30.48 33.46 34.89
342.42 344.61 348.84 349.42 369.45 380.44
0.0870 0.0868 0.0871 0.0874 0.0905 0.0917
0.2263 0.2266 0.2322 0.2319 0.2744 0.2934
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Fig. 10. X-ray diffraction pattern for AlTiN coating and pre-treated/coated samples.
crystallite size. When comparing the adhesive failure of the coating (Lc2) it can be seen that pre-treated samples at pressures 0.3 MPa and 0.5 MPa showed significant improvement. The increased adhesion strength is possibly due to better bonding between the substrate and the coating material which occurred owing to the surface roughening and uniformity of the stresses achieved by the micro abrasive blasting operation.
its quantitative determination is difficult. Hence it t is mostly described qualitatively. However, indentation of the coated surface with ramped/ varying loading helps in determining the mechanics which is responsible for the coating failure. The critical load for failure may give some quantitative measure. The critical load is the minimum value of the tangential force that can initiate and perpetuate the oscillations in forces during the generation of the wear track [36]. Normally, the critical load is distinguished into two parts in case of the scratch operation. The minimum load at which the first failure occurs, such as propagation and generation of cracks, is indicative of the cohesive failure and is referred as the first critical load (Lc1). When the total delamination of the film occurs, or more accurately the substrate gets exposed, then it indicates an adhesive failure and it is termed as the second critical load (Lc2)[37]. The critical load values have been determined by observing the variation in the acoustic emission signal. The critical loads, Lc1 and Lc2, are listed in Table 2 for all the samples. There is no significant difference between the Lc1 for the pre-treated and only coated samples. However, in the case of post-treated samples, a slight improvement can be seen. It may be contributed to the increased hardness of the samples as well as the improved intermolecular bonding due to reduced
3.7. Tool Wear Study Machining performance of the cutting tools is analyzed during the turning of Nimonic C 263. Flank wear of the cutting tools for various conditions is studied under an optical microscope as well as scanning electron microscope and is considered as a criterion for tool wear analysis. Fig.13. represents the progression of the flank wear with the machining length measured in mm. The dominant wear mode for all the tools was adhesion and abrasion as well as diffusion at certain localized sites[38]. The uncoated tool failed after 75 mm of cutting length as its edge has undergone catastrophic failure due to its insufficient strength for machining of the nickel-based superalloys. Apart from this notch wear, the uncoated tool
Fig. 11. Variation in the peak position due to the pre and post mechanical treatment of the samples. 452
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Fig. 12. Scanning electron microscopy images of the adhesion test for various samples.
machining operation. However, the hybrid coated AlTiN tools was adequately capable of withstanding this high temperature. The aluminum phase from the coating reacts with the surrounding air forming an aluminum oxide layer which is passive as well as chemically stable in nature[30]. This layer acts as a thermal barrier between the tool-workpiece tribo-pair. But with increased machining length, the tool undergoes severe nose wear as well as notching due to the abrasive action of the flowing chips containing hard abrasive particles present in the workpiece [39]. When comparing the machining performance of micro blasted tools, no such failure (edge fracture or sudden wear) was observed over the cutting edge except in the case of coated/micro basted (0.2) tool. The
Table 2 Critical load values for the as coated and micro blasted samples. Sample
Lc1 (N)
Lc2 (N)
Only coated Pre-treatment(0.1 MPa)/Coating Pre-treatment(0.3 MPa)/Coating Pre-treatment(0.5 MPa)/Coating Coating/Post-treatment (0.1 MPa) Coating/Post-treatment (0.2 MPa)
0.4 0.35 0.43 0.54 0.58 0.63
0.80 0.87 1.50 1.61 1.05 1.20
has reached a value of ∼530 μm. The strength of the tool decreases as it undergoes more deformation due to thermal softening during the
Fig. 13. Progression of flank wear for the coated as well as pre and post treated samples. 453
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tools. This is due to the improved hardness of the coated cutting tool as well as induced compressive residual stresses. However, when the post micro blasting pressure reaches a value of 0.2 MPa, the failure of the cutting tool occurred near the cutting edge. The high-pressure impingement may have caused the removal of the coating at localized sites, which in turn exposed the cemented carbide material during the machining operation. The increase in the surface roughness of the coated/post-treated tools resulted in reduction of formed BUE which is observed in only coated tool (lower surface roughness causes sticking of the flowing material over the tool surface). In the case of the pre-treated tool i.e., micro blasting at 0.1 MPa, high BUE formation occurred. The coated cutting tool subjected to micro blasting pre-treatment at 0.5 MPa performed better than the previous i.e. tool subjected to micro abrasive blasting pre-treatment at pressure 0.3 MPa which underwent high nose wear.
post treated tool at 0.2 MPa pressure underwent catastrophic failure on the principal cutting edge as notch wear reached a value of ∼341 μm. This may be due to the fact that the micro blasting of the cutting tool at such high pressure has resulted in coating delamination and subsequent exposure of the cutting tool substrate of lower strength i.e. low hardness value in comparison to coating. However, the post treated cutting tool at 0.1 MPa outperformed well in terms of flank wear. This behaviour of the cutting tool is correlated to the increased strength due to induced compressive residual stresses thus resulting in reduced tool wear. The pre-treated cutting tool at 0.1 MPa underwent almost similar flank wear as that of pre-treated at 0.3 MPa. However, in comparison to only coated tool, this reduction is about 13.09 % and 23.22 % for pre-treated (0.1 MPa) and pre-treated (0.3 MPa) respectively. The cutting tools subjected to micro blasting pre-treatment at 0.5 MPa have performed the best amongst all the tools as the flank wear got reduced to a value of ∼99 μm. However, in the final stage, it underwent severe chipping possibly due to high forces or stresses exerted by the entangled chips. The pre-treatment blasting helps in improving the adhesion between the substrate as well as the coating due to surface roughening caused by wedged shape particles impingement, which in turn helps in reducing the flank wear. From the study of the rake and flank surfaces of the uncoated tools, BUE formation is observed near the nose while adhesion of the work material as well as oxidation of the tool material are also identified near the fractured edge. On the rake face (Fig.14) abrasion marks can be clearly seen which appears in the form of striation. At certain localized sites, groove and ridge (striation) formation took place due to the continuous flow of the chips over the rake surface. The poor thermal conductivity of nickel-based superalloys causes oxidation of the tool material at certain sites because of the increased temperature. Flank wear studies of the uncoated and coated tools proved that the uncoated tool underwent cutting-edge fracture due to high thermal stresses during the machining process. In the case of a coated tool, the failure of the cutting tool occurred due to the chipping and frittering near the cutting edge, which is depicted in Fig. 15. The coated cutting tool also has undergone high nose wear possibly due to the work hardening as well as burr formation on the workpiece. In the case of coated and micro blasted (0.1 MPa) tool, no significant wear near the cutting edge or nose was found in comparison to other
4. Conclusions In this work, an attempt has been made to understand the basic physics of how the mechanical characteristics of the as coated and micro blasted pre and post-treated cutting tools can be utilized for improving the performance of cutting tools during machining of nickelbased superalloy Nimonic C 263. From the present study the following conclusions are drawn:
• The • • • •
cutting tools coated with hybrid technique (Arc enhanced HiPIMS) have exhibited excellent surface characteristics in comparison to conventional CAE- PVD technique. The pre-coated surface micro blasting causes an increase in nucleation sites for the coating growth while the post-coating micro blasting causes evenness in surface topography of the cutting tools. The fine abrasive impingement on cutting tools causes abrasive action and helps in achieving peaks of uniform heights for better adhesion. The tool subjected to micro blasting showed improved surface and sub-surface properties in terms of hardness, adhesion and crystallite refinement. Tools subjected to blasting before coating deposition at 0.5 MPa showed excellent wear characteristics in comparison to all other substrate treated tools as the flank wear reduced to a value of 49.25
Fig. 14. Wear mechanism for the uncoated tool during machining of Nimonic C 263. 454
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Fig. 15. SEM images of flank wear after 150 mm cut of Nimonic C 263 work material.
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References
% in comparison to as coated tools without undergoing high nose wear. Post-treated tools subjected to blasting pressure of 0.1 MPa showed a reduction in tool flank wear by 45.57 % in comparison to as coated tools. The main type of wear observed during machining of Nimonic C 263 by different tools is abrasion, micro-chipping and adhesion. BUE formation also occurred for certain tools.
[1] Prengel HG, Jindal PC, Wendt KH, Santhanam AT, Hegde PL, Penich RM. A new class of high performance PVD coatings for carbide cutting tools. Surf Coatings Technol 2001;139:25–34. https://doi.org/10.1016/S0257-8972(00)01080-X. [2] Prengel HG, Pfouts WR, Santhanam AT. State of the art in hard coatings for carbide cutting tools. Surf Coatings Technol 1998;102:183–90. https://doi.org/10.1016/ S0257-8972(96)03061-7. [3] Haubner R, Lessiak M, Pitonak R, Köpf A, Weissenbacher R. Evolution of conventional hard coatings for its use on cutting tools. Int J Refract Met Hard Mater 2017;62:210–8. https://doi.org/10.1016/j.ijrmhm.2016.05.009. [4] Peng Z, Miao H, Qi L, Yang S, Liu C. Hard and wear-resistant titanium nitride coatings for cemented carbide cutting tools by pulsed high energy density plasma. Acta Mater 2003;51:3085–94. https://doi.org/10.1016/S1359-6454(03)00119-8. [5] zhao Ding X, Bui CT, Zeng XT. Abrasive wear resistance of Ti1 - xAlxN hard coatings deposited by a vacuum arc system with lateral rotating cathodes. Surf Coatings Technol 2008;203:680–4. https://doi.org/10.1016/j.surfcoat.2008.08.019. [6] Kadlec S, Musil J, Valvoda V, Münz WD, Petersein H, Schroeder J. TiN films grown by reactive magnetron sputtering with enhanced ionization at low discharge pressures. Vacuum 1990;41:2233–8. https://doi.org/10.1016/0042-207X(90)94233-G. [7] Knotek O, Lugscheider E, Löffler F, Beele W, Barimani C. Arc evaporation of
From the results, it can be seen that post and pre-micro blasting helps in improving the tool performance and hence can be utilized as an economically viable technique of surface treatment provided optimal pressure values during the micro blasting are maintained.
455
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A. Singh et al.
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
[20]
[21]
[22]
[23] Kennedy DM, Vahey J, Hanney D. Micro shot blasting of machine tools for improving surface finish and reducing cutting forces in manufacturing. Mater Des 2005;26:203–8. https://doi.org/10.1016/j.matdes.2004.02.013. [24] Tanaka S, Shirochi T, Nishizawa H, Metoki K, Miura H, Hara H, et al. Surface & Coatings Technology Micro-blasting effect on fracture resistance of PVD-AlTiN coated cemented carbide cutting tools. Surf Coat Technol 2016;308:337–40. https://doi.org/10.1016/j.surfcoat.2016.07.094. [25] Bouzakis KD, Michailidis N, Hadjiyiannis S, Efstathiou K, Pavlidou E, Erkens G, et al. Improvement of PVD coated inserts cutting performance, through appropriate mechanical treatments of substrate and coating surface. Surf Coatings Technol 2001;146-147:443–50. https://doi.org/10.1016/S0257-8972(01)01485-2. [26] Tönshoff HK, Mohlfeld a. Surface treatment of cutting tool substrates. Int J Mach Tools Manuf 1998;38:469–76. https://doi.org/10.1016/S0890-6955(97)00091-6. [27] Klocke F, Krieg T. Coated Tools for Metal Cutting – Features and Applications. CIRP Ann - Manuf Technol 1999;48:515–25. https://doi.org/10.1016/S0007-8506(07) 63231-4. [28] Takadoum J, Bennani HH. Influence of substrate roughness and coating thickness on adhesion, friction and wear of TiN films. Surf Coatings Technol 1997;96:272–82. https://doi.org/10.1016/S0257-8972(97)00182-5. [29] Bouzakis KD, Skordaris G, Michailidis N, Asimakopoulos A, Erkens G. Effect on PVD coated cemented carbide inserts cutting performance of micro-blasting and lapping of their substrates. Surf Coatings Technol 2005;200:128–32. https://doi.org/10. 1016/j.surfcoat.2005.02.119. [30] Endrino JL, Fox-Rabinovich GS, Hard AlTiN Gey C. AlCrN PVD coatings for machining of austenitic stainless steel. Surf Coatings Technol 2006;200:6840–5. https://doi.org/10.1016/j.surfcoat.2005.10.030. [31] Leyland A, Matthews A. On the significance of the H/E ratio in wear control: A nanocomposite coating approach to optimised tribological behaviour. Wear 2000;246:1–11. https://doi.org/10.1016/S0043-1648(00)00488-9. [32] Beake BD, Ranganathan N. An investigation of the nanoindentation and nano/ micro-tribological behaviour of monolayer, bilayer and trilayer coatings on cemented carbide. Mater Sci Eng A 2006;423:46–51. https://doi.org/10.1016/j.msea. 2005.11.066. [33] Xi Y, Gao K, Pang X, Yang H, Xiong X, Li H, et al. Film thickness effect on texture and residual stress sign transition in sputtered TiN thin films. Ceram Int 2017;43:11992–7. https://doi.org/10.1016/j.ceramint.2017.06.050. [34] Ungár T. Microstructural parameters from X-ray diffraction peak broadening. Scr Mater 2004;51:777–81. https://doi.org/10.1016/j.scriptamat.2004.05.007. [35] Haršáni M, Ghafoor N, Calamba K, Zacková P, Sahul M, Vopát T, et al. Adhesivedeformation relationships and mechanical properties of nc-AlCrN/a-SiNxhard coatings deposited at different bias voltages. Thin Solid Films 2018;650:11–9. https://doi.org/10.1016/j.tsf.2018.02.006. [36] Wang Q, Zhou F, Yan J. Evaluating mechanical properties and crack resistance of CrN, CrTiN, CrAlN and CrTiAlN coatings by nanoindentation and scratch tests. Surf Coatings Technol 2016;285:203–13. https://doi.org/10.1016/j.surfcoat.2015.11. 040. [37] Perry AJ. Scratch adhesion testing of hard coatings. Thin Solid Films 1983;107:167–80. https://doi.org/10.1016/0040-6090(83)90019-6. [38] Zhu D, Zhang X, Ding H. Tool wear characteristics in machining of nickel-based superalloys. Int J Mach Tools Manuf 2013;64:60–77. https://doi.org/10.1016/j. ijmachtools.2012.08.001. [39] Cantero JL, Díaz-Álvarez J, Miguélez MH, Marín NC. Analysis of tool wear patterns in finishing turning of Inconel 718. Wear 2013;297:885–94. https://doi.org/10. 1016/j.wear.2012.11.004.
multicomponent MCrAlY cathodes. Surf Coatings Technol 1995;74–75:118–22. https://doi.org/10.1016/0257-8972(94)08208-1. LaGrange DD, LaGrange T, Santana A, Jähnig R. Macroparticles formation in cathodic arc deposition of nitride coatings from TiNb alloy cathodes. J Vac Sci Technol A Vacuum, Surfaces, Film 2017;35:021309https://doi.org/10.1116/1. 4975638. Schneider JM, Helmersson U, Kouznetsov V, Maca K, Petrov I. A novel pulsed magnetron sputter technique utilizing very high target power densities 1999 122:290–3. Helmersson U, Lattemann M, Bohlmark J, Ehiasarian AP, Tomas J. Review Ionized physical vapor deposition (IPVD): A review of technology and applications. Thin solid films 2006;513:1–24. https://doi.org/10.1016/j.tsf.2006.03.033. Alami J, Eklund P, Emmerlich J, Wilhelmsson O, Jansson U. High-power impulse magnetron sputtering of Ti – Si – C thin films from a Ti 3 SiC 2 compound target. Thin solid films 2006;515:1731–6. https://doi.org/10.1016/j.tsf.2006.06.015. Luo Q, Yang S, Cooke KE. Surface & Coatings Technology Hybrid HIPIMS and DC magnetron sputtering deposition of TiN coatings : Deposition rate, structure and tribological properties. Surf Coat Technol 2013;236:13–21. https://doi.org/10. 1016/j.surfcoat.2013.07.003. Zhou H, Zheng J, Gui B, Geng D, Wang Q. AlTiCrN coatings deposited by hybrid HIPIMS/DC magnetron co-sputtering. Vacuum 2017;136:129–36. https://doi.org/ 10.1016/j.vacuum.2016.11.021. Viana R, de Lima MSF, Sales WF, da Silva WM, Machado ÁR. Laser texturing of substrate of coated tools - Performance during machining and in adhesion tests. Surf Coatings Technol 2015;276:485–501. https://doi.org/10.1016/j.surfcoat.2015.06. 025. Bouzakis KD, Tsouknidas A, Skordaris G, Bouzakis E, Makrimallakis S, Gerardis S, et al. Optimization of wet or dry microblasting on PVD films by various Al2O3 grain sizes for improving the coated tools’ cutting performance. Tribol Ind 2011;33:49–56. https://doi.org/10.1016/j.cirp.2011.03.012. Bouzakis KD, Skordaris G, Gerardis S, Katirtzoglou G, Makrimallakis S, Pappa M, et al. The effect of substrate pretreatments and HPPMS-deposited adhesive interlayers’ materials on the cutting performance of coated cemented carbide inserts. CIRP Ann - Manuf Technol 2010;59:73–6. https://doi.org/10.1016/j.cirp.2010.03. 065. Klocke F, Gorgels C, Bouzakis E, Stuckenberg A. Tool life increase of coated carbide tools by micro blasting. Prod Eng 2009;3:453–9. https://doi.org/10.1007/s11740009-0173-1. Fernández-Abia AI, Barreiro J, López De Lacalle LN, González-Madruga D. Effect of mechanical pre-treatments in the behaviour of nanostructured PVD-coated tools in turning. Int J Adv Manuf Technol 2014;73:1119–32. https://doi.org/10.1007/ s00170-014-5844-1. Denkena B, Lucas A, Bassett E. Effects of the cutting edge microgeometry on tool wear and its thermo-mechanical load. CIRP Ann - Manuf Technol 2011;60:73–6. https://doi.org/10.1016/j.cirp.2011.03.098. Tönshoff HK, Karpuschewski B, Mohlfeld A, Seegers H. Influence of subsurface properties on the adhesion strength of sputtered hard coatings. Surf Coatings Technol 1999;116–119:524–9. https://doi.org/10.1016/S0257-8972(99)00226-1. Shen X, Wang X, Sun F, Ding C. Diamond & Related Materials Sandblasting pretreatment for deposition of diamond fi lms on WC-Co hard metal substrates. Diam Relat Mater 2017;73:7–14. https://doi.org/10.1016/j.diamond.2016.10.025. Bouzakis KD, Bouzakis E, Skordaris G, Makrimallakis S, Tsouknidas A, Katirtzoglou G, et al. Effect of PVD films wet micro-blasting by various Al2O3 grain sizes on the wear behaviour of coated tools. Surf Coatings Technol 2011;205. https://doi.org/ 10.1016/j.surfcoat.2011.03.046. S128–32.
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Influence of dry micro abrasive blasting on the physical and mechanical characteristics of hybrid PVD-AlTiN coated tools
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Abhishek Singh, S. Ghosh , S. Aravindan Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi Hauz Khas, Delhi, 110016, India
A R T I C LE I N FO
A B S T R A C T
Keywords: Micro abrasive blasting HiPIMS Morphology Superficial Hardness
The current study investigates the effect of the micro abrasive blasting (MAB) on the physical and mechanical characteristics of the cutting tools before and after coating deposition. Cutting tools were subjected to micro blasting by alumina (Al2O3) grains at varying pressure so as to improve the efficacy of the coating process. AlTiN coating of thickness 1.45 μm was deposited onto the tool surface by arc enhanced high power impulse magnetron sputtering (HiPIMS) hybrid deposition technique. The coatings were characterized using nano indentation, atomic force microscopy and micro scratch test. The results of nano indentations on the coated surface revealed the influence of the micro abrasive blasting technique and pressure on the superficial hardness. Surface morphology results showed better-adhered surface in case of cutting tools subjected to micro abrasive blasting before the deposition due to an increase in density of the nucleation sites for growth of aluminum which can be judged with the help of higher aluminum content in the energy dispersive x-ray analysis. The film adhesion of the coating onto the tool substrate is observed to be improved significantly with an increase in blasting pressure in the case of the samples subjected to micro abrasive blasting before coating. Additionally, X-ray diffraction analysis was performed to investigate crystallographic phases. The attained results provide insight concerning the optimum selection of micro abrasive blasting technique along with the pressure, for enhancing the cutting performance of coated tools during the machining of nickel-based superalloy Nimonic C 263.
1. Introduction Tribology at the chip-tool interface is one of the most important factors while cutting difficult to machine materials. Hence, tool surface properties and cutting environments (cooling and lubrication) have become major factors in controlling the machinability of these materials. Due to potential environmental hazards and high recycling cost of cutting fluids, industries prefer dry cutting processes. Coated tools offer a solution in terms of economic and eco-friendly machining. Improved mechanical and tribological properties of the coating are required to carry out dry or near dry machining at higher speeds. Hard coatings over cutting tools have been studied in recent past due to its greater wear resistance, oxidation resistance, high hardness and high-temperature operational capabilities[1–5]. Amongst them, physical vapor deposition (PVD) is one of the most widely used coating methods for industrial application over chemical vapor deposition. But the coating deposition by conventional techniques such as magnetron sputtering, and cathodic arc evaporation brings out various drawbacks. Magnetron sputtering results in low ionization while cathodic arc evaporation results in droplet formation (cause of poor adhesion between the
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substrate and coating material)[6–8]. The introduction of the high power impulse magnetron sputtering (HiPIMS) in 1999 by Schneider et al. [9] eliminated most of the drawbacks of these conventional PVD techniques by achieving coatings with improved coating structure, enhanced adhesion over the substrate and proper control over other deposition parameters[10,11]. But low deposition rates still remain a problem for the utilization of this technique in commercial applications. [12]. In order, to overcome these limitations a novel hybrid deposition technique has been developed that combines high power impulse magnetron sputtering (HiPIMS) with arc evaporation technique. This utilizes the benefits of both the techniques and promotes the formation of a high-density coating structure with improved friction characteristics. This process enables more direct control over the deposition process. It utilizes pulses of high power density in the range of few kW/ cm2 and low duty cycles (< 10%) resulting in improved ionization and higher deposition rates. Some studies have been carried out utilizing HiPIMS coating deposition technique and it has been found that there has been an improvement in the mechanical properties of the coating structure. Zhou et al.[13] reported that hybrid HiPIMS/DC magnetron sputtering
Corresponding author. E-mail address: [email protected] (S. Ghosh).
https://doi.org/10.1016/j.jmapro.2018.11.024 Received 26 July 2018; Received in revised form 22 November 2018; Accepted 24 November 2018 1526-6125/ © 2018 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.
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behaviour of these coatings is still unknown.
resulted in proper control over the deposition parameters as coating thickness, bias voltage, pulse rate, transition sharpness etc. Nowadays, various types of coatings are commercially used over the cutting tools due to their improved performance during the modern machining processes such as high speed, dry environments, heavy cutting loads, and difficult-to-machine materials. Though their sustainability over the cutting tools become pivotal when working at elevated temperatures. Therefore, in order to enhance the physical and mechanical properties of the coated tools various surface treatment techniques such as laser treatment, mechanical polishing, mechanical treatment, heat treatment etc. are employed[14,15]. Out of all the mentioned processes, micro abrasive blasting is gaining popularity due to low processing cost, improved coating performance and no heat affected zone formation (as in the case of laser texturing). The technique has been utilized both as a substrate treatment (known as pre-treatment) as well as a post coating treatment (called as post-treatment) to improve the adhesion between coating and substrate, film hardness, friction characteristics and fatigue life. The effect of micro blasting on various physical and mechanical characteristics have been reported by various researchers but are contradictory in nature[16–18]. Abia et al. [18] observed that the pre-treatment of the tool using glass microspheres for 30 seconds caused changes in the geometry of the cutting edges which in turn affected the efficiency of the coating deposition. The cutting edges of these samples show more roundness as compared to the untreated sample. Denkena et al. [19] analyzed that the changes in the geometry of cutting edges were caused due to the pressure exerted by the impingement of the abrasive particles. The radius of the cutting edge should be controlled for achieving good adhesion strength and reduced residual stress. Tonshoff et al.[20] have reported that the micro abrasive blasting of the carbide substrate before application of coating leads to increased adhesion properties between the coating material and the substrate. This is mainly due to an increase in the nucleation sites during deposition. Similar observation during the deposition of diamond films on the WC substrate was made by other researchers[21]. Other researches focussed on different aspects of micro abrasive blasting, but no detailed study has been done for understanding the efficacy of the process. Bouzakis et al.[16]reported that accumulation of high value of the residual stress at the cutting edge may cause detachment of the coating which in turn reduces the performance of coated tool during machining. Abia et al. [18] have revealed that pre-treatment of the substrate by glass microspheres has increased the surface roughness value of the substrate surface due to the impact of the microspheres resulting in superficial micro-cracks in the substrate. The pre-treated samples exhibited the presence of radial fissures and this corresponds to poor adhesion. Post coating treatment causes changes in characteristics such as cutting-edge geometry, composition, hardness and crystallographic phases. Bouzakis et al. [22] reported that micro abrasive blasting using Al2O3 grains induces stresses in the substrate of TiAlN coating which deteriorates the film ductility thus increasing its brittleness and hardness. In another study, Kennedy et al. [23] observed that the use of post coating treatment could be beneficial in terms of improving the cuttingedge strength however; this behaviour is limited to a specific blasting pressure. Micro abrasive blasting of the cutting tool can be useful in enhancing the fracture resistance of the coatings with proper control over the certain parameters[24]. From the available literature, it has been found that various studies are carried out to improve the performance of the cutting tools through micro abrasive blasting process, but no detailed study has been done for understanding the efficacy of the process. Therefore, appropriate experimental and analytical investigations were carried out in order to examine the effect of micro-blasting parameters on the coating properties. This work is to comprehend the effect of micro abrasive blasting as substrate treatment and coating treatment at varying pressure on the newly proposed hybrid technique as the metallurgical and mechanical
2. Experimental Details 2.1. Substrate treatment Micro abrasive blasting process involves the impingement of the wedge-shaped Al2O3 particles onto the substrate of the cutting tools for approximately 30 seconds. The used Al2O3 particles are of a size in the range of 10-20 μm. The distance between the blasting nozzle and the cutting inserts has been kept at 120 mm. The pre-treatment was carried out at three different pressure i.e. 0.1 MPa, 0.3 MPa and 0.5 MPa to analyze its effects at varying conditions. 2.2. Coating deposition AlTiN coatings were deposited on to the K grade cemented carbide inserts having CNMA 120408 geometry using Arc evaporation enhanced HIPIMS technique using AlTi targets which were fabricated by powder metallurgy route. All the substrates were chronologically cleaned in ultrasonic baths of acetone and alcohol for 4 minutes each, before being loaded into the vacuum chamber and were dried using pure nitrogen. The chamber was evacuated to a pressure of 5 × 10-3 Pa and the cutting inserts were heated up to a temperature of 420 °C before the coating deposition. Pre-sputtering of the target and plasma cleaning of the substrate was carried out in argon gas filled chamber with the aim of removing the impurities from the substrate and target surfaces. The deposition of 1.45 μm film of AlTiN took 51 minutes at a deposition temperature in the range of 420-450 °C. The thickness of the deposited coating was measured and verified using X-ray fluorescence technique. 2.3. Coating Treatment The coated samples were subjected to dry micro abrasive blasting process at two different pressures of 0.1 MPa and 0.2 MPa. The pressure values were so selected to understand the detrimental as well as benign effects of such post treatment. The process duration of the treatment was kept as 4 seconds. Al2O3 particles, used for the micro abrasive blasting, are having a size in the range of 10-20 μm and have wedgeshaped geometry. The distance between the blasting nozzle and the cutting inserts has been kept at 120 mm and is referred as the standoff distance (Fig. 1). In this study, the sample utilized for post-treatment doesn’t undergo any type of pre-treatment before coating deposition. 2.4. Coating Characterization Various experimental techniques were used for evaluating the physical, mechanical and tribological properties of the coated and uncoated specimens. X-ray diffraction technique was adopted to characterize the crystal structure of the as-coated, micro blasted/coated and coated/micro
Fig. 1. Micro abrasive blasting setup showing important parameters. 447
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From the microstructural analysis of the samples after coating deposition, it is found that the coating exhibits good adhesion on the pretreated substrates. This is correlated to the dense surface structure as well as fewer dislocations or defects. It can be also observed that no micro/macro holes or pores or droplet formation take place in hybrid deposited AlTiN coatings unlike the coatings deposited by conventional cathodic arc evaporation or magnetron sputtering technique (Fig. 3). On comparing the micrographs of the pre-treated/coated samples at the varying pressure no significant difference can be observed on the surface topography (Fig. 4). However, the effect of pressure can be better attributed to the enhanced adhesion of the coating, which is also later confirmed by performing adhesion tests and subsequent performance of the coated tools during the machining operation. The effect of the micro abrasive blasting can also be examined and correlated with the help of the EDS data which reveals that pre-treatment had caused an increase in the Al content from 32.118 % in asdeposited to 36.546 % in pre-treated sample (0.1 MPa) due to an increase in the density of the nucleation sites for growth of Al (Fig. 5).
blasted samples using Philips Panalytical X'pert, Cu Ka with a scanning speed of 1.0°/min, the step of 0.05°, and diffraction angles 2Ɵ between 20° and 80°. The surface roughness and topography of the samples were studied by means of atomic force microscopy (AFM, Make: Bruker Dimension icon with ScanAsyst) technique and Scanning Electron Microscopy technique respectively. The elastic modulus and hardness of the samples were evaluated using Hysitron Nano Indentor (TI 950 TriboIndentor) with loading and unloading time of 10 seconds and holding time of 2 seconds. 30 indents were taken at various localized sites for achieving the accuracy in measurement. The peak load (5000 μN) was selected in such a way that the effect or influence of surface roughness on the obtained results can be avoided whilst ensuring the nano-indentation depth to be 1/10th of the film thickness so that load-invariant coating hardness could be measured along with coating dominated elastic modulus. Micro scratch tests were performed so as to determine the friction and wear characteristics, microscopic deformation and micro-cracking behaviour of the coated samples through critical load analysis. The testing was performed at a ramp load of 1 N/min at peak load of 2 N. The adhesion of the samples was studied qualitatively by Rockwell HRC test using diamond indenter at a load of 1500 N.
3.2. Effect of MAB post-treatment on the coating morphology Post-treatment for the coated samples was carried out at two different pressures i.e. 0.1 MPa and 0.2 MPa. The surface morphology study reveals that the micro blasting of the coated surfaces results in an increase in the surface roughness of the coated samples due to the wedging action (Fig. 6). However, this effect is insignificant when the blasting pressure is 0.1 MPa.
2.5. Machining Performance Evaluation The cutting experiments were performed on CNC Leadwell T-6 turning centre for the nickel-based superalloy Nimonic C 263. Tool wear was measured at fixed values of cutting speed (60 m/min), feed (0.16 mm/rev) and depth of cut of 1 mm. The length of the cut was kept constant at 150 mm and each experiment was conducted two times for validating the obtained results. Flank wear of the worn surfaces was measured under an optical microscope (Zeiss AxioVisionSE64) while wear mechanism was studied using a scanning electron microscope. All the experiments were performed under dry condition.
3.3. Effect of MAB pre-treatment and post-treatment on the surface roughness of the coating The effect of microblasting on the substrate as well as coating can also be deduced by investigating another important aspect i.e. surface roughness. It is evident that micro abrasive blasting pre-treatment, as well as post-treatment causes a certain degree of roughening of the substrate and coating. The roughening is due to the impact of impinged abrasive particles. Uniform roughness is desirable over the substrate for achieving proper adhesion with the coated material. In the case of the coated films, surface roughness of optimum range is desirable. Takadoum and Bennani have observed that tool with higher surface roughness undergoes severe wear of coating. The tool with low surface roughness values may cause sticking with the tool-workpiece tribo-pair (increased contact area) resulting in higher tool wear thereby decreasing the tool life [28]. So the value of surface roughness should be in optimum range and are contained by a low coefficient of friction thus making chip flow easier. This fact reduces the tool wear thereby improving the tool life. The surface roughness measured using atomic force microscopy techniques shown in Fig. 7. The cutting tools were fabricated and manufactured using powder metallurgy and various other manufacturing processes to obtain the desired shape. The obtained surfaces are of varying roughness or have non-uniformity in their surface roughness values. These values are very low and hence certain surface modification technique needs to be adopted to obtain good adherence between the substrate and deposited film. The upper surfaces of the tools also have cobalt in a smeared (less contact area for mechanical interlocking) form which prevents good adhesion with the coated surface. The use of mechanical treatment technique i.e. micro abrasive blasting results in surface roughening of the substrate due to the impinged abrasive particles (Fig. 8). With the increase in the pressure for the impingement, the value of the surface roughness increases. When the pressure was 0.1 MPa, the value of surface roughness was found to be 80 nm which has increased to 209 nm at 0.5 MPa pressure. The increased roughness of the substrate is helpful in enhancing adhesion characteristics between the substrate and coating by promoting mechanical interlocking [29]. While comparing the surface
3. Results and Discussions 3.1. Effect of MAB pre-treatment on the substrate and coating morphology The surface morphology of the specimens was examined to understand the difference in the substrate conditions due to varying pressure. Micro abrasive blasting of the cutting tools causes variation in the surface topography. Cobalt present in the cemented carbide tools is more ductile in comparison to the tungsten carbide grains. During micro blasting, Co grains in the upper surface got depleted from the substrate (surface to be coated) resulting in the formation of new roughness peaks of the tungsten carbide grains of smaller heights. These peaks thus contribute to the substrate-coating adhesion enhancement due to mechanical anchoring. From Fig.2, it can be seen that the increase in blasting pressure results in an increase in the surface roughness of the samples as well as more exposure of the new carbide grains which may be helpful in improved adhesion between the substrate and coating[25]. It is noteworthy that the removal of the Co from the upper surface doesn’t affect its binding behaviour at the sub-surface layers of the cutting tool. However, the surface roughening observed on the tool substrate also depends upon the size of the abrasive which caused the material removal due to the impinging action of the wedge-shaped alumina. Hence the proper selection of the abrasive grain size is necessary. Micro blasting was carried out using fine grains as they lead to less deformation of the sub-surface layers. The abrasive effect of micro abrasive blasting with fine grain is also instrumental as it may lead to the constant stress level of the same degree as that of the ground surface [26]. The use of coarse grains results in more plastic deformation and leads to a high value of compressive stresses in comparison to the ground surface (uncoated tool without any surface treatment) which is not desired for the process [27]. 448
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Fig. 2. Substrate morphology at low and high magnifications showing surface roughening effect at varying pressure for the uncoated inserts.
Fig. 3. Scanning electron microscopy at low and high magnifications for the only coated samples in case of hybrid and conventional PVD technique.
Fig. 4. Scanning electron microscopy at low magnification for pre-treated/coated samples at varying pressure. Pre-treatment (0.1 MPa)/Coating Pre-treatment (0.3 MPa)/Coating Pre-treatment(0.5 MPa)/Coating
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Fig. 5. Energy dispersive x-ray spectroscopy for the as deposited and pre-treated(0.1 MPa)/coated sample.
roughness of the only coated samples and pre-treated/coated samples no significant difference in values was observed. Post-treatment of the coated films results in an increase in the values of the surface roughness. It is due to the impinging action of the wedgeshaped alumina particles. The surface roughness of samples reached a maximum of 170 nm in the case of coated and micro blasted sample (0.2 MPa). 3.4. Effect of MAB pre-treatment and post-treatment on the fracture toughness and hardness of the coated film The peak load is selected so that the indentation depth is less than 1/10th of the film thickness. Hardness of the samples has been measured and studied using nanoindentation tests at a peak load of 5000 μN. The hardness of the as deposited AlTiN film by the hybrid technique was 29.83 GPa which is much higher as compared to AlTiN films deposited by cathodic arc deposition technique[30]. The micro blasting of the substrate and the films induce compressive residual stresses which result in the variation in the hardness values. The results achieved through nanoindentation tests can be listed as
Fig. 7. Surface roughness values for cutting tools under various conditions.
ability of the coating to withstand high loads without undergoing fracture. So from the Table 1. It can be seen the post-treated samples exhibited higher plastic deformation resistance capability in comparison to the only coated samples. (b) The slight increase in the hardness of the pre-treated samples in comparison to the only coated may be due to the improved surface properties which occurred because of the uniformity in the stresses over the substrate during the coating deposition produced by the micro abrasive blasting. (c) Post-treatment of samples have resulted in good improvement of the superficial hardness which is due to the induced compressive stresses on the film. The change in the hardness also causes a diminution in the penetration depth during the nanoindentation. The increase in micro abrasive blasting pressure from 0.1 MPa to 0.2 MPa further increases the hardness value. (d) In order to clearly demonstrate the behaviour of the various samples the loading-unloading curves are shown in the Fig.9. It
(a) The value of H/E and H3/E2 presents the same variation trend as hardness in Table 1. These ratios reflect elastic strain to failure and plastic deformation resistance of the material. Thus taking into account the values of H, H/E and H3/E2 the samples subjected to post micro blasting (0.2 MPa) should exhibit strongest crack resistance while the only coated samples exhibit poorest again crack resistance. The high value of H/E can be beneficial as it provides a higher elastic strain to break and allow coatings to remain in the elastic limit during the loading conditions[31]. Beake and Ranganathan [32] have reported that the high H/E ratio is closely related to the tribological behaviour of the samples along with the hardness value. Similarly, H3/E2 ratio represents the ability of the coating to resist plastic deformation. Higher the value higher will be the
Fig. 6. Field emission scanning electron micrographs for coated/post-treated samples showing an increase in the surface roughening. 450
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Fig. 8. Surface roughening effect of the micro abrasive particles on the substrate (cemented carbide).
represents the variation in penetration depth with the applied load. The curves do not indicate any “pop in and pop out” which is an indicative of no crack formation over the coated surface. The hardness value in the case of coated and micro blasted (0.2 MPa) sample was maximum (34.89 GPa) while in the case of the only coated sample it is limited to 29.83 GPa. This increase in the hardness can also be correlated with the decrease in the penetration depth of the indenter or vice- versa.
3.5. Effect of MAB pre-treatment and post-treatment on the crystallographic phases and crystallite size coated films Fig. 9. Loading- unloading curves for only coated, pre and post treated samples.
X-Ray diffraction for the only coated and pre-treated and posttreated samples were carried out for determining whether any metallurgical changes such as phase transformation are taking place. The variation in the crystal structure or phase can be established primarily through shifts in the peak positions. During the analysis, the coating showed a cubic aluminum nitride (AlN) structure which is generally responsible for high hardness and wear resistance of the coating (Fig. 10). The XRD patterns of all the samples show the similar sequence of the peaks in terms of count. Hence it can be concluded that samples do not undergo any change in the phases due to micro abrasive blasting. The broadening of the peaks divulges the variation in the crystallite size [33]. Comparing the XRD spectra for the only coated and pre-treated samples, slight variation in the peak position was found on the higher degrees. This variation can be correlated to the released stresses due to micro abrasive blasting. The increase in the nucleation of the new grains due to micro abrasive blasting causes changes in the sub-surface morphology which in turn causes the densification of the coating structure which is confirmed by low-intensity peaks in case of micro blasted and coated samples (0.5 MPa) in comparison to only coated samples. However, at low pressure micro abrasive blasting, no such effect was observed and the value of the intensities remain the same. While comparing the post-treated sample spectra with the only deposited, the shifting of the peaks occurred on the lower angles (Fig. 11.) possibly due to the induced compressive stresses which cause dislocations as well as refinement of crystallites because of the impinging effect of the abrasive grains [34].
3.6. Effect of MAB pre-treatment and post-treatment on the adhesion of the coated films To evaluate the effect of micro abrasive blasting on the AlTiN films deposited by the hybrid technique, Rockwell HRC indentations tests were carried out on the film surface by making use of diamond indenter at a load of 1500 N. The diamond indenter penetrates the coated film inducing deformation plastically into the substrate and causing cracking, chipping and de-bonding of the coating. The Rockwell imprints were observed by scanning electron microscopy for qualitative analysis of the adhesion and are presented in Fig. 12. It can be observed that the coatings exhibited good adhesion for all of the samples with the generation of very few radial cracks (adhesion of class 1, EN-1071-8). It can be also observed that the microchipping occurred in case of only coated samples near the edges while this got significantly reduced in the case of the pretreated samples. Pre-treatment of the samples causes the surface roughening effect which improves the adhesion between the substrate and the coating. In the case of post-treated samples, an improvement in the adhesion can be seen. Post-treatment of the samples have resulted in radial cracks near the edges. These cracks are in micrometres in length and occur due to the indentation. The cracks gradually propagate within the columnar structure of the PVD coating, and then moves to the cobalt matrix of the WC-Co substrate [35]. The adhesion of the coating depends on different factors and hence
Table 1 Mechanical Properties of the samples under varying conditions. Sample
Hardness, H(GPa)
Elastic Modulus, E (GPa)
H/E
H3/E2 (GPa)
Only coated Pre-treatment(0.1 MPa)/Coating Pre-treatment(0.3 MPa)/Coating Pre-treatment(0.5 MPa)/Coating Coating/Post-treatment (0.1 MPa) Coating/Post-treatment (0.2 MPa)
29.83 29.97 30.46 30.48 33.46 34.89
342.42 344.61 348.84 349.42 369.45 380.44
0.0870 0.0868 0.0871 0.0874 0.0905 0.0917
0.2263 0.2266 0.2322 0.2319 0.2744 0.2934
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Fig. 10. X-ray diffraction pattern for AlTiN coating and pre-treated/coated samples.
crystallite size. When comparing the adhesive failure of the coating (Lc2) it can be seen that pre-treated samples at pressures 0.3 MPa and 0.5 MPa showed significant improvement. The increased adhesion strength is possibly due to better bonding between the substrate and the coating material which occurred owing to the surface roughening and uniformity of the stresses achieved by the micro abrasive blasting operation.
its quantitative determination is difficult. Hence it t is mostly described qualitatively. However, indentation of the coated surface with ramped/ varying loading helps in determining the mechanics which is responsible for the coating failure. The critical load for failure may give some quantitative measure. The critical load is the minimum value of the tangential force that can initiate and perpetuate the oscillations in forces during the generation of the wear track [36]. Normally, the critical load is distinguished into two parts in case of the scratch operation. The minimum load at which the first failure occurs, such as propagation and generation of cracks, is indicative of the cohesive failure and is referred as the first critical load (Lc1). When the total delamination of the film occurs, or more accurately the substrate gets exposed, then it indicates an adhesive failure and it is termed as the second critical load (Lc2)[37]. The critical load values have been determined by observing the variation in the acoustic emission signal. The critical loads, Lc1 and Lc2, are listed in Table 2 for all the samples. There is no significant difference between the Lc1 for the pre-treated and only coated samples. However, in the case of post-treated samples, a slight improvement can be seen. It may be contributed to the increased hardness of the samples as well as the improved intermolecular bonding due to reduced
3.7. Tool Wear Study Machining performance of the cutting tools is analyzed during the turning of Nimonic C 263. Flank wear of the cutting tools for various conditions is studied under an optical microscope as well as scanning electron microscope and is considered as a criterion for tool wear analysis. Fig.13. represents the progression of the flank wear with the machining length measured in mm. The dominant wear mode for all the tools was adhesion and abrasion as well as diffusion at certain localized sites[38]. The uncoated tool failed after 75 mm of cutting length as its edge has undergone catastrophic failure due to its insufficient strength for machining of the nickel-based superalloys. Apart from this notch wear, the uncoated tool
Fig. 11. Variation in the peak position due to the pre and post mechanical treatment of the samples. 452
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Fig. 12. Scanning electron microscopy images of the adhesion test for various samples.
machining operation. However, the hybrid coated AlTiN tools was adequately capable of withstanding this high temperature. The aluminum phase from the coating reacts with the surrounding air forming an aluminum oxide layer which is passive as well as chemically stable in nature[30]. This layer acts as a thermal barrier between the tool-workpiece tribo-pair. But with increased machining length, the tool undergoes severe nose wear as well as notching due to the abrasive action of the flowing chips containing hard abrasive particles present in the workpiece [39]. When comparing the machining performance of micro blasted tools, no such failure (edge fracture or sudden wear) was observed over the cutting edge except in the case of coated/micro basted (0.2) tool. The
Table 2 Critical load values for the as coated and micro blasted samples. Sample
Lc1 (N)
Lc2 (N)
Only coated Pre-treatment(0.1 MPa)/Coating Pre-treatment(0.3 MPa)/Coating Pre-treatment(0.5 MPa)/Coating Coating/Post-treatment (0.1 MPa) Coating/Post-treatment (0.2 MPa)
0.4 0.35 0.43 0.54 0.58 0.63
0.80 0.87 1.50 1.61 1.05 1.20
has reached a value of ∼530 μm. The strength of the tool decreases as it undergoes more deformation due to thermal softening during the
Fig. 13. Progression of flank wear for the coated as well as pre and post treated samples. 453
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tools. This is due to the improved hardness of the coated cutting tool as well as induced compressive residual stresses. However, when the post micro blasting pressure reaches a value of 0.2 MPa, the failure of the cutting tool occurred near the cutting edge. The high-pressure impingement may have caused the removal of the coating at localized sites, which in turn exposed the cemented carbide material during the machining operation. The increase in the surface roughness of the coated/post-treated tools resulted in reduction of formed BUE which is observed in only coated tool (lower surface roughness causes sticking of the flowing material over the tool surface). In the case of the pre-treated tool i.e., micro blasting at 0.1 MPa, high BUE formation occurred. The coated cutting tool subjected to micro blasting pre-treatment at 0.5 MPa performed better than the previous i.e. tool subjected to micro abrasive blasting pre-treatment at pressure 0.3 MPa which underwent high nose wear.
post treated tool at 0.2 MPa pressure underwent catastrophic failure on the principal cutting edge as notch wear reached a value of ∼341 μm. This may be due to the fact that the micro blasting of the cutting tool at such high pressure has resulted in coating delamination and subsequent exposure of the cutting tool substrate of lower strength i.e. low hardness value in comparison to coating. However, the post treated cutting tool at 0.1 MPa outperformed well in terms of flank wear. This behaviour of the cutting tool is correlated to the increased strength due to induced compressive residual stresses thus resulting in reduced tool wear. The pre-treated cutting tool at 0.1 MPa underwent almost similar flank wear as that of pre-treated at 0.3 MPa. However, in comparison to only coated tool, this reduction is about 13.09 % and 23.22 % for pre-treated (0.1 MPa) and pre-treated (0.3 MPa) respectively. The cutting tools subjected to micro blasting pre-treatment at 0.5 MPa have performed the best amongst all the tools as the flank wear got reduced to a value of ∼99 μm. However, in the final stage, it underwent severe chipping possibly due to high forces or stresses exerted by the entangled chips. The pre-treatment blasting helps in improving the adhesion between the substrate as well as the coating due to surface roughening caused by wedged shape particles impingement, which in turn helps in reducing the flank wear. From the study of the rake and flank surfaces of the uncoated tools, BUE formation is observed near the nose while adhesion of the work material as well as oxidation of the tool material are also identified near the fractured edge. On the rake face (Fig.14) abrasion marks can be clearly seen which appears in the form of striation. At certain localized sites, groove and ridge (striation) formation took place due to the continuous flow of the chips over the rake surface. The poor thermal conductivity of nickel-based superalloys causes oxidation of the tool material at certain sites because of the increased temperature. Flank wear studies of the uncoated and coated tools proved that the uncoated tool underwent cutting-edge fracture due to high thermal stresses during the machining process. In the case of a coated tool, the failure of the cutting tool occurred due to the chipping and frittering near the cutting edge, which is depicted in Fig. 15. The coated cutting tool also has undergone high nose wear possibly due to the work hardening as well as burr formation on the workpiece. In the case of coated and micro blasted (0.1 MPa) tool, no significant wear near the cutting edge or nose was found in comparison to other
4. Conclusions In this work, an attempt has been made to understand the basic physics of how the mechanical characteristics of the as coated and micro blasted pre and post-treated cutting tools can be utilized for improving the performance of cutting tools during machining of nickelbased superalloy Nimonic C 263. From the present study the following conclusions are drawn:
• The • • • •
cutting tools coated with hybrid technique (Arc enhanced HiPIMS) have exhibited excellent surface characteristics in comparison to conventional CAE- PVD technique. The pre-coated surface micro blasting causes an increase in nucleation sites for the coating growth while the post-coating micro blasting causes evenness in surface topography of the cutting tools. The fine abrasive impingement on cutting tools causes abrasive action and helps in achieving peaks of uniform heights for better adhesion. The tool subjected to micro blasting showed improved surface and sub-surface properties in terms of hardness, adhesion and crystallite refinement. Tools subjected to blasting before coating deposition at 0.5 MPa showed excellent wear characteristics in comparison to all other substrate treated tools as the flank wear reduced to a value of 49.25
Fig. 14. Wear mechanism for the uncoated tool during machining of Nimonic C 263. 454
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Fig. 15. SEM images of flank wear after 150 mm cut of Nimonic C 263 work material.
• •
References
% in comparison to as coated tools without undergoing high nose wear. Post-treated tools subjected to blasting pressure of 0.1 MPa showed a reduction in tool flank wear by 45.57 % in comparison to as coated tools. The main type of wear observed during machining of Nimonic C 263 by different tools is abrasion, micro-chipping and adhesion. BUE formation also occurred for certain tools.
[1] Prengel HG, Jindal PC, Wendt KH, Santhanam AT, Hegde PL, Penich RM. A new class of high performance PVD coatings for carbide cutting tools. Surf Coatings Technol 2001;139:25–34. https://doi.org/10.1016/S0257-8972(00)01080-X. [2] Prengel HG, Pfouts WR, Santhanam AT. State of the art in hard coatings for carbide cutting tools. Surf Coatings Technol 1998;102:183–90. https://doi.org/10.1016/ S0257-8972(96)03061-7. [3] Haubner R, Lessiak M, Pitonak R, Köpf A, Weissenbacher R. Evolution of conventional hard coatings for its use on cutting tools. Int J Refract Met Hard Mater 2017;62:210–8. https://doi.org/10.1016/j.ijrmhm.2016.05.009. [4] Peng Z, Miao H, Qi L, Yang S, Liu C. Hard and wear-resistant titanium nitride coatings for cemented carbide cutting tools by pulsed high energy density plasma. Acta Mater 2003;51:3085–94. https://doi.org/10.1016/S1359-6454(03)00119-8. [5] zhao Ding X, Bui CT, Zeng XT. Abrasive wear resistance of Ti1 - xAlxN hard coatings deposited by a vacuum arc system with lateral rotating cathodes. Surf Coatings Technol 2008;203:680–4. https://doi.org/10.1016/j.surfcoat.2008.08.019. [6] Kadlec S, Musil J, Valvoda V, Münz WD, Petersein H, Schroeder J. TiN films grown by reactive magnetron sputtering with enhanced ionization at low discharge pressures. Vacuum 1990;41:2233–8. https://doi.org/10.1016/0042-207X(90)94233-G. [7] Knotek O, Lugscheider E, Löffler F, Beele W, Barimani C. Arc evaporation of
From the results, it can be seen that post and pre-micro blasting helps in improving the tool performance and hence can be utilized as an economically viable technique of surface treatment provided optimal pressure values during the micro blasting are maintained.
455
Journal of Manufacturing Processes 37 (2019) 446–456
A. Singh et al.
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
[20]
[21]
[22]
[23] Kennedy DM, Vahey J, Hanney D. Micro shot blasting of machine tools for improving surface finish and reducing cutting forces in manufacturing. Mater Des 2005;26:203–8. https://doi.org/10.1016/j.matdes.2004.02.013. [24] Tanaka S, Shirochi T, Nishizawa H, Metoki K, Miura H, Hara H, et al. Surface & Coatings Technology Micro-blasting effect on fracture resistance of PVD-AlTiN coated cemented carbide cutting tools. Surf Coat Technol 2016;308:337–40. https://doi.org/10.1016/j.surfcoat.2016.07.094. [25] Bouzakis KD, Michailidis N, Hadjiyiannis S, Efstathiou K, Pavlidou E, Erkens G, et al. Improvement of PVD coated inserts cutting performance, through appropriate mechanical treatments of substrate and coating surface. Surf Coatings Technol 2001;146-147:443–50. https://doi.org/10.1016/S0257-8972(01)01485-2. [26] Tönshoff HK, Mohlfeld a. Surface treatment of cutting tool substrates. Int J Mach Tools Manuf 1998;38:469–76. https://doi.org/10.1016/S0890-6955(97)00091-6. [27] Klocke F, Krieg T. Coated Tools for Metal Cutting – Features and Applications. CIRP Ann - Manuf Technol 1999;48:515–25. https://doi.org/10.1016/S0007-8506(07) 63231-4. [28] Takadoum J, Bennani HH. Influence of substrate roughness and coating thickness on adhesion, friction and wear of TiN films. Surf Coatings Technol 1997;96:272–82. https://doi.org/10.1016/S0257-8972(97)00182-5. [29] Bouzakis KD, Skordaris G, Michailidis N, Asimakopoulos A, Erkens G. Effect on PVD coated cemented carbide inserts cutting performance of micro-blasting and lapping of their substrates. Surf Coatings Technol 2005;200:128–32. https://doi.org/10. 1016/j.surfcoat.2005.02.119. [30] Endrino JL, Fox-Rabinovich GS, Hard AlTiN Gey C. AlCrN PVD coatings for machining of austenitic stainless steel. Surf Coatings Technol 2006;200:6840–5. https://doi.org/10.1016/j.surfcoat.2005.10.030. [31] Leyland A, Matthews A. On the significance of the H/E ratio in wear control: A nanocomposite coating approach to optimised tribological behaviour. Wear 2000;246:1–11. https://doi.org/10.1016/S0043-1648(00)00488-9. [32] Beake BD, Ranganathan N. An investigation of the nanoindentation and nano/ micro-tribological behaviour of monolayer, bilayer and trilayer coatings on cemented carbide. Mater Sci Eng A 2006;423:46–51. https://doi.org/10.1016/j.msea. 2005.11.066. [33] Xi Y, Gao K, Pang X, Yang H, Xiong X, Li H, et al. Film thickness effect on texture and residual stress sign transition in sputtered TiN thin films. Ceram Int 2017;43:11992–7. https://doi.org/10.1016/j.ceramint.2017.06.050. [34] Ungár T. Microstructural parameters from X-ray diffraction peak broadening. Scr Mater 2004;51:777–81. https://doi.org/10.1016/j.scriptamat.2004.05.007. [35] Haršáni M, Ghafoor N, Calamba K, Zacková P, Sahul M, Vopát T, et al. Adhesivedeformation relationships and mechanical properties of nc-AlCrN/a-SiNxhard coatings deposited at different bias voltages. Thin Solid Films 2018;650:11–9. https://doi.org/10.1016/j.tsf.2018.02.006. [36] Wang Q, Zhou F, Yan J. Evaluating mechanical properties and crack resistance of CrN, CrTiN, CrAlN and CrTiAlN coatings by nanoindentation and scratch tests. Surf Coatings Technol 2016;285:203–13. https://doi.org/10.1016/j.surfcoat.2015.11. 040. [37] Perry AJ. Scratch adhesion testing of hard coatings. Thin Solid Films 1983;107:167–80. https://doi.org/10.1016/0040-6090(83)90019-6. [38] Zhu D, Zhang X, Ding H. Tool wear characteristics in machining of nickel-based superalloys. Int J Mach Tools Manuf 2013;64:60–77. https://doi.org/10.1016/j. ijmachtools.2012.08.001. [39] Cantero JL, Díaz-Álvarez J, Miguélez MH, Marín NC. Analysis of tool wear patterns in finishing turning of Inconel 718. Wear 2013;297:885–94. https://doi.org/10. 1016/j.wear.2012.11.004.
multicomponent MCrAlY cathodes. Surf Coatings Technol 1995;74–75:118–22. https://doi.org/10.1016/0257-8972(94)08208-1. LaGrange DD, LaGrange T, Santana A, Jähnig R. Macroparticles formation in cathodic arc deposition of nitride coatings from TiNb alloy cathodes. J Vac Sci Technol A Vacuum, Surfaces, Film 2017;35:021309https://doi.org/10.1116/1. 4975638. Schneider JM, Helmersson U, Kouznetsov V, Maca K, Petrov I. A novel pulsed magnetron sputter technique utilizing very high target power densities 1999 122:290–3. Helmersson U, Lattemann M, Bohlmark J, Ehiasarian AP, Tomas J. Review Ionized physical vapor deposition (IPVD): A review of technology and applications. Thin solid films 2006;513:1–24. https://doi.org/10.1016/j.tsf.2006.03.033. Alami J, Eklund P, Emmerlich J, Wilhelmsson O, Jansson U. High-power impulse magnetron sputtering of Ti – Si – C thin films from a Ti 3 SiC 2 compound target. Thin solid films 2006;515:1731–6. https://doi.org/10.1016/j.tsf.2006.06.015. Luo Q, Yang S, Cooke KE. Surface & Coatings Technology Hybrid HIPIMS and DC magnetron sputtering deposition of TiN coatings : Deposition rate, structure and tribological properties. Surf Coat Technol 2013;236:13–21. https://doi.org/10. 1016/j.surfcoat.2013.07.003. Zhou H, Zheng J, Gui B, Geng D, Wang Q. AlTiCrN coatings deposited by hybrid HIPIMS/DC magnetron co-sputtering. Vacuum 2017;136:129–36. https://doi.org/ 10.1016/j.vacuum.2016.11.021. Viana R, de Lima MSF, Sales WF, da Silva WM, Machado ÁR. Laser texturing of substrate of coated tools - Performance during machining and in adhesion tests. Surf Coatings Technol 2015;276:485–501. https://doi.org/10.1016/j.surfcoat.2015.06. 025. Bouzakis KD, Tsouknidas A, Skordaris G, Bouzakis E, Makrimallakis S, Gerardis S, et al. Optimization of wet or dry microblasting on PVD films by various Al2O3 grain sizes for improving the coated tools’ cutting performance. Tribol Ind 2011;33:49–56. https://doi.org/10.1016/j.cirp.2011.03.012. Bouzakis KD, Skordaris G, Gerardis S, Katirtzoglou G, Makrimallakis S, Pappa M, et al. The effect of substrate pretreatments and HPPMS-deposited adhesive interlayers’ materials on the cutting performance of coated cemented carbide inserts. CIRP Ann - Manuf Technol 2010;59:73–6. https://doi.org/10.1016/j.cirp.2010.03. 065. Klocke F, Gorgels C, Bouzakis E, Stuckenberg A. Tool life increase of coated carbide tools by micro blasting. Prod Eng 2009;3:453–9. https://doi.org/10.1007/s11740009-0173-1. Fernández-Abia AI, Barreiro J, López De Lacalle LN, González-Madruga D. Effect of mechanical pre-treatments in the behaviour of nanostructured PVD-coated tools in turning. Int J Adv Manuf Technol 2014;73:1119–32. https://doi.org/10.1007/ s00170-014-5844-1. Denkena B, Lucas A, Bassett E. Effects of the cutting edge microgeometry on tool wear and its thermo-mechanical load. CIRP Ann - Manuf Technol 2011;60:73–6. https://doi.org/10.1016/j.cirp.2011.03.098. Tönshoff HK, Karpuschewski B, Mohlfeld A, Seegers H. Influence of subsurface properties on the adhesion strength of sputtered hard coatings. Surf Coatings Technol 1999;116–119:524–9. https://doi.org/10.1016/S0257-8972(99)00226-1. Shen X, Wang X, Sun F, Ding C. Diamond & Related Materials Sandblasting pretreatment for deposition of diamond fi lms on WC-Co hard metal substrates. Diam Relat Mater 2017;73:7–14. https://doi.org/10.1016/j.diamond.2016.10.025. Bouzakis KD, Bouzakis E, Skordaris G, Makrimallakis S, Tsouknidas A, Katirtzoglou G, et al. Effect of PVD films wet micro-blasting by various Al2O3 grain sizes on the wear behaviour of coated tools. Surf Coatings Technol 2011;205. https://doi.org/ 10.1016/j.surfcoat.2011.03.046. S128–32.
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