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Microstructure, surface topography and sliding wear behaviour of titanium based coating on AISI 1040 steel by magnetron sputtering
archives of civil and mechanical engineering 17 (2017) 281–292
Available online at www.sciencedirect.com
ScienceDirect journal homepage: http://www.elsevier.com/locate/acme
Original Research Article
Microstructure, surface topography and sliding wear behaviour of titanium based coating on AISI 1040 steel by magnetron sputtering Selvakumar N a,1, Malkiya Rasalin Prince R b,* a
Centre for Nano Science & Technology, Department of Mechanical Engineering, Mepco Schlenk Engineering College, Sivakasi 626 005, Tamil Nadu, India b Department of Mechanical Engineering, Bethlahem Institute of Engineering, Karungal, Tamilnadu, India
article info
abstract
Article history:
In the present study, 2% B4C reinforced with Ti–6Al–4V composite coatings on AISI 1040 steel
Received 20 May 2016
plates were coated using magnetron sputtering. The microstructure and surface morphol-
Accepted 16 October 2016
ogies of the coated specimen were analyzed using SEM, XRD, EDS and AFM. The uniform
Available online
coating thickness of 75 nm and 110 nm on smooth surfaces have been obtained for 0.5 h and 1 h coating time respectively. Under the normal load of 2 N and 3 N, Ti–Al–V–B4C coatings
Keywords:
wear analysis were performed and resulted in excellent wear rate with lower coefficient of
Magnetron sputtering
friction. Ti–Al–V–B4C thin film shows the nano hardness value of 7.2 GPa and 9.7 GPa for 0.5 h
Ball on disc
and 1 h coating time and elastic modulus of 204 GPa. The surface roughness (Ra) of 0.5 h and
Flash temperature
1 h coating are 3.393 nm and 17.433 nm respectively. The addition of B4C particles reinforced
AISI 1040 steel
Ti–Al–V composite coatings showed enhanced nano hardness and improved the wear
Ti–6Al–4V–2B4C
resistance with decrease in the coefficient of friction. The amount of heat generated during wear test has been calculated. Ti–Al–V–B4C composite coatings were exposed to lowest wear rates among all loading conditions and thus signifying that it could be a promising alternative to other hard coatings. # 2016 Politechnika Wrocławska. Published by Elsevier Sp. z o.o. All rights reserved.
1.
Introduction
Medium carbon steel is the major constituent to fabricate components in engineering, mining, construction and agricultural field due to its better strength and higher hardness. Most of the sliding materials mainly failed due to wear, so wearable
materials have always been the best topic for the respective researchers. The uses of innovative coatings play an important role for the production of thin films with outstanding properties. In particular, the manufacturing of Ti–Al–V–B4C coating is a promising way to achieve thin films with outstanding properties. The most noted hardness of B4C is its excellent resistance to wear. Magnetron sputtering has
* Corresponding author. E-mail addresses: [email protected] (S. N), [email protected] (M.R.P. R). 1 Fax: +91 04562 2235111. http://dx.doi.org/10.1016/j.acme.2016.10.005 1644-9665/# 2016 Politechnika Wrocławska. Published by Elsevier Sp. z o.o. All rights reserved.
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become the choice for the deposition of a wide-range of industrially important hard coatings. Titanium Grade-5 (Ti–6Al–4V) alloy is mostly used in aerospace, medical and aircraft industries due to its unique strength-to-weight ratio. Carbide and nitride coatings improve the strength, hardness and wear resistance of steel. Boron carbide coating has found variety of applications such as plasma-faced components in fusion reactors, electromagnetic radiation field, coatings on nozzles, high precision tooling dies. Magnetron sputtering is an enormously adaptable technique for the deposition of highquality with well-adhered films [1]. The development of NbC coating on AISI 1040 steel exhibited low coefficient of friction, higher wear rate, compact, smooth, porosity free and homogeneous [2]. Hard coating with nitride and carbide is a general route for developing the wear resistance of metals. In general nitrides and carbides exhibit low coefficient of friction, excellent wear resistance and higher hardness [3]. Surface hardness of the steel has been improved via hard coatings and a mixed phase of film has been obtained. Among the ferrous materials, the AISI 1040 steel is the most popular material for industries [4]. A pin-on-disc experiment shows that the CrCN coatings exhibit lower friction coefficient and remarkable wear resistance better than CrN coating. [5]. Wear behaviour of TiAlN/ CNx coatings on cemented carbide tool steel were improved, the coefficient friction and wear depth of the coatings were reduced [6]. Ni/WC nanocomposite coatings exhibit improved nanohardness and better resistance to wear compared with pure Ni coatings. The nanoidentation was found that Ni/nanoWC composite coatings exhibit enhanced nanohardness as compared with pure nickel coatings [7]. Boron carbide coating has found a wide range of applications, including fusion reactor components, coating on nozzles, high precision tooling dies, radiation shields due to its superior physical and mechanical properties. B4C coated steel substrate shows high hardness and it can be used as inertial confinement in fusion reactors [8]. However, in order to afford adequate wear, the
coating need to be uniform, adhesive, pore free and wear resistant. Therefore, in the present study, Ti–Al–V–2B4C coatings were selected as wear resistive coatings for AISI 1040 steels in order to develop its wear resistance.
2.
Materials and experimental details
2.1.
Materials
Titanium alloy Ti–6Al–4V has notable mechanical properties at room temperature, having better tensile strength. Ti–6Al–4V has exceptional resistance to corrosion in most natural and various industrial processing environments. Boron carbide is an extremely hardest ceramic material and ranking third behind diamond and cubic boron nitride. The chemical composition of AISI 1040 steel is C 0.35-0.44%, Si 0.20%, Mn 0.75%, S 0.05%, P 0.04% and balance Fe [9].
2.2.
XRD analysis
Crystal structure and orientation of the Ti–6Al–4V–2B4C coating were studied by X-ray diffractometer with monochromated Cu Ka radiation (K = 1.54060 Å) at 60 kV over the range of 2u = 20–808 with a step size of 0.0170 and a step time of 3.1750 s. The phase purity and grain size were determined by XRD analysis.
2.3.
Target and substrate preparation
The powders form of Ti, Al, V and B4C were used as target material. The target was prepared with Ti–6Al–4V–2B4C. The powders were milled and mixed properly via mechanical milling under argon atmosphere. This mechanical milling process provided homogeneous mixture of the composites for formulating the target. Fig. 1 shows the scanning electron microscopic image of the pre compacted powders. All the pre
Fig. 1 – SEM image of pre compacted Ti–6Al–4V–2B4C powders.
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on the holder, by maintaining a target to substrate distance of 60 mm. Sputtering chamber was evacuated to 1 105 N/m2 and the substrates were blasted using argon ion (Ar+). The substrate coating temperature was maintained at about 100 20 8C. The coating time for all specimens was fixed as 0.5 h, 1 h respectively. For all the coatings the sputtering gas pressure is kept in the range of (Ar) 0.001 to 0.1 N/m2. Ti–6Al– 4V–2B4C adhesion layers were deposited on the substrate uniformly.
2.5.
Fig. 2 – EDS pattern of Ti–6Al–4V–2B4C target.
compacted powder particles were in irregular, angular shape with rough surfaces, in order to study the microstructure of the Ti, Al, V, B4C powders before preparing target. Chen et al. [10] explained the method of achieving 75% relative density of compact for Ti–Al–V with a compaction pressure of 700 MPa. The green compact of Ti–6Al–4V–2B4C was uniaxially compressed by compression testing machine. Total required amount of Ti, Al, V and B4C milled powders were pressed uniaxially with a pressure of 650 MPa at room temperature. The green compact was sintered with an inert gas circulated electric muffle furnace at 950 8C for a holding period of 1 h. To avoid oxidization, the green compacts in the beginning were protected with inert argon atmosphere in the furnace. After that the sintered target was brought into room temperature under furnace cooling conditions. The target with a diameter of 54 mm and thickness of 3 mm was obtained. Fig. 2 shows the Energy Dispersive Spectrum (EDS) analysis of Ti–6Al–4V–2B4C target. EDS analysis confirms the presence of Ti, Al, V, B and C. The elemental peak of Ti was identified as the major peak with high intensity. The other elements like Al, V, B and C were identified with minor peaks. In EDS analysis, no oxide peak was observed. EDS analysis suggests that B and C particles in the target were stable during sintering time and no intermetallic layer were found in the target. AISI 1040 steel plates were used as the substrate for the required coating. AISI 1040 steel plate samples of 60 mm diameter and 3 mm thickness were prepared by 350 grit waterproof silicon carbide grinding wheels and then by 60, 80, 120, 220, 320 grade Al2O3 waterproof papers to get a smooth mirror polishing surface. After that, the organic impurities present in the surface were cleaned with n-propanol and acetone. Then the cleaned samples were loaded in the sputtering chamber for coating. The loaded substrates were further cleaned by argon ion bombardment for achieving better bonding of coatings.
2.4.
AFM analysis
AFM is suitable for obtaining three-dimensional topographic information of thin film coatings for structural analysis on the nano scale. The topography of the coating is analyzed with AFM (XE 70, Park Systems–S. Korea). The surface roughness and particle size are examined using AFM analysis. AFM nano indentation was also used to study the mechanical properties of the coatings with a variation of loads. Analysis of surface quality and roughness of Ti–6Al–4V–2B4C thin film were carried out using AFM method. This was verified by performing force measurements on underlying AISI 1040 steel substrate at a sufficiently small loading force to ensure little indentation.
2.6.
Wear test
After coating of Ti–6Al–4V–2B4C on AISI 1040 substrate, the dry sliding wear test was conducted using a ball on disc wear tester. Fig. 3 shows the ball on disc arrangement that was used for the wear test. The contact steel ball was cleaned with acetone for better surface contact between ball and disc. The steel ball of 10 mm in diameter with a hardness value of 450 VHN was used for wear test and it is fixed in the holder. The wear test parameters were noted and given in Table 1. Wear test was conducted on the coated specimen by applying load on steel ball with varying track radius of 20 mm, 25 mm, 30 mm and 35 mm respectively. Wear tests were carried out with two normal loads (2 N, 3 N) and different sliding velocities (0.52, 0.65, 0.79 and 0.92 m/s). The sliding velocity was calculated from the track radius and sliding speed. The wear testing was carried out with a fixed time of 2 min for all the tests. After each test the wear loss of the coated disc was weighed using a sensitive electronic balance with an accuracy of 0.01 mg to find out the weight loss. The weight loss was converted into volume loss. The wear rate was calculated from
Deposition of Ti–Al–V–2B4C films
Sputter deposition technique is a physical vapour deposition method for preparing thin films using a DC magnetron sputtering process. These methods consist of emitting material from a target that is a source (Ti–6Al–4V–2B4C) onto a substrate (AISI 1040). The target and substrate were mounted
Fig. 3 – Schematic diagram of ball-on-disc wear testing machine.
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Table 1 – Wear and friction test parameters of Ti–6Al–4V– 2B4C coated sample. Parameters
Values
Applied load (N) No. of trail for each samples Velocity (m/s) Speed of the disc (rpm) Wear track diameter (mm) Working temperature (8C) Relative humidity (%) Test duration (s) Test balls Environment
2, 3 3 0.52, 0.65, 0.79 and 0.92 500 20, 25, 30 and 35 26 65 120 Steel Dry air
the wear volume and the sliding distance. Frictional force was measured from the recorded graph during wear test. The wear volume, wear rate, specific wear rate and coefficient of friction were calculated by using the following Eqs. (1)–(4) [11].
Wear loss Density
(1)
Wear volume Sliding distance
(2)
Wear volume ¼
Wear rate ¼
Specific wear rate ¼
Wear volume Load Sliding distance
(3)
Frictional force Applied load
(4)
Coefficient of friction ¼
3.
Results and discussion
3.1.
XRD analysis
Fig. 4 shows the XRD pattern with the peaks Ti, Al, V and B4C. The elemental confirmation was made by XRD study and Ti (JCPDS 89-2762) exhibited a peak at 35.18, indicating a strong (1 0 0) orientation in the coating. Ti peaks with 2u values of
Fig. 4 – XRD pattern of the Ti–6Al–4V–2B4C coated AISI 1040 steel.
40.28, 62.98, 70.68, 76.18 and 77.38 belong to the crystal planes of (1 0 1), (1 1 0), (1 0 3), (1 1 2) and (2 0 1) respectively. Aluminium peaks in the plane (1 1 1), (2 0 0) and (3 1 1) were confirmed using the JCPDS file no. 89-4037 with 2u values of 38.48 and 44.88. It can be matched with the JCPDS file no. 22-1058 for vanadium with characteristic peaks in the plane of (1 1 0) corresponding 2u value of 42.18. The presence of boron carbide particles in the coating were represented by the characteristic peaks in the plane of (2 0 0), (2 1 4) and (0 2 7) with 2u values of 53.48, 58.88 and 65.18. The results matched very well with the JCPDS file No. 75-0424. It is noted that no oxide peak was observed in the XRD analysis. This suggests that no intermetallic layer were found during coating and B4C particles were stable during coating time. XRD patterns confirm the presence of B4C in the coating. It was observed that the peaks of Ti, Al, V and B4C were wider. The broadness of the peaks deals with the size of the particles and the randomness with which they are orientated. Hence from this analysis it is clear that the particles present in the coatings are in nano scale. Fig. 5 shows the Energy Dispersive Spectrum (EDS) analysis of Ti–6Al–4V–2B4C coating. From Fig. 5, the various elements in the coating were identified through different peaks. The various elements identified in the coating are Ti, Al, V, B, C, Si, Mn, S, P and Fe. The elements of substrate are shown in Fig. 5, the presence of C, Si, Mn, S, P and Fe confirms the chemical composition of the substrate. No oxide peak was observed in the EDS analysis.
3.2.
AFM analysis
AFM profiles in Figs. 6 and 7 demonstrate the topography of Ti– 6Al–4V–2B4C coated AISI 1040 steel substrate. The thickness of coated Ti–6Al–4V–2B4C thin films was evaluated by AFM method, the overall thickness of the coating was determined around 75 nm throughout the coating for 0.5 h coating time. Fig. 6(a) displays two-dimensional (2D) AFM images of Ti–6Al– 4V–2B4C films with 0.5 h coating duration. The AFM image reveals the waviness surface texture of Ti–6Al–4V–2B4C thin films. Waviness is the measure of extensively spaced component in the surface pattern and is associated to roughness. The average surface roughness Ra on the coating was 3.946– 3.393 nm. The average distance between the highest peak and bottom most valley (Rz) is calculated as 24.451 nm. The average
Fig. 5 – EDS pattern of Ti–6Al–4V–2B4C coated AISI 1040 steel.
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Fig. 6 – Topography of 0.5 h coated Ti–6Al–4V–2B4C film (a) 2D and (b) 3D.
mean square Rq value of the coating is obtained as 4.529 nm. It is noted that the surface roughness of Ti–6Al–4V–2B4C coating is lower than that of the TiAlN/CNx coatings [12]. Fig. 6(b) shows three-dimensional (3D) AFM images of Ti– 6Al–4V–2B4C films. The surface of the coatings is relatively smooth and the surface looks like valley and hill shape. The surface of the coatings and film growth were in ordered manner. The ‘‘valley’’ section is comparatively smooth, while the ‘‘hill’’ sector encloses many crystal-like structures that exhibit certain orientations. It is understood that reduction in grain size may moderate the roughness of the film surface and thus the wear behaviour of the coating was enriched. Fig. 7(a) shows the two-dimensional (2D) image of the Ti– 6Al–4V–2B4C coatings with 1 h coating time. The coating thickness of 110 nm has been obtained for 1 h coating duration. The surface roughness Ra of the Ti–6Al–4V–2B4C coating was 15.749–17.433 nm. The average distance between the highest peak and lowest valley, Rz, is calculated as 82.564 nm. The Rq value of the coating is obtained as 20.212 nm. Due to the increase in coating thickness and constant substrate temperature, the value of surface roughness improved with coating time. This is due to the more
deposition time that admits the formation of coarse structures which leads to an increase in surface roughness. Fig. 7(b) shows three-dimensional (3D) AFM images of Ti– 6Al–4V–2B4C films. The surface looks like a honeycomb structure. It is clearly noted that the surface roughness of the coated surface has been enriched. The maximum grain size of the coatings was observed that of 25 nm and the average grain size of the coatings was observed that of 4 nm. The overall height of the coating was detected around 25 nm throughout the coating. The value of the peak position was measured which is approximately 74 nm. Both the coatings were having homogeneous microstructure observed by AFM. The Ti–6Al–4V–2B4C thin film coatings reveal similar dense, homogeneous microstructure even though the grain size of the coating increasing with increasing the coating time.
3.3. Effect of hardness on Ti–6Al–4V–2B4C coated AISI 1040 steel AFM nano indention is an alternative technique to evaluate the mechanical properties of thin film coatings on a very small scale. Even though thin film coatings with coating thickness
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Fig. 7 – Topography of 1 h coated Ti–6Al–4V–2B4C film (a) 2D and (b) 3D.
lesser than 5 nm can be calculated. Nano technique allows the user to measure the nanoscale hardness of thin film coatings. Nano indentation technique consists of 3 phases such as loading, holding and unloading processes. The contact mode AFM probe can be applied to obtain the image. The penetration of the indentation is measured from the AFM image. During indentation, a force–displacement (F-D) curve has been obtained and nano hardness of the coating has been calculated from F-D curve. At first the indentation process progresses, during the indentation amount of force required for indentation gradually increases which is specified by the red line. The maximum applying load as 4 nN, after applying the specified load the tip freely penetrates the coating which is displayed by the inclined blue line. After that, the tip is slowly removed from the coating. The F-D curve of the coating has been obtained for the load input of 4 nN. From these F-D curves, the nano hardness (H) of the coating can be calculated by using the formula (5) [13]. H¼
P 24:5ðhc Þ2
(5)
where P – maximum applied load, hc – penetration depth. Fig. 8(a–b) represents the nanoindentation force– displacement curve of 0.5 h coating and 1 h coating time.
Ti–6Al–4V–2B4C coated AISI 1040 steel shows the maximum elastic modulus of 204 GPa. The calculated value of hardness for the Ti–6Al–4V–2B4C coating under 0.5 h and 1 h coating time is 7.2 GPa and 9.7 GPa respectively [14]. Initially the hardness of the coating increased because of small penetration depth, which is generally recognized as the conversion between only elastic to elastic/plastic contact takes place and at this stage the obtained mean contact pressure does not exactly denote the actual hardness of the coating. The mean interaction pressure represents the hardness of the coating only under the condition of a fully developed plastic zone. When the coating has no plastic zone, or formed only partially plastic zone, the mean contact pressure is less than the hardness of the coating. The hardness value of the coating initially rises with the depth of penetration to a maximum value and then gradually decreases to a constant value. During this stage, the value of the hardness decreases and reaches a constant value, which could be observed as true hardness of the Ti–6Al–4V– 2B4C coating. The hardness behaviour of the Ti–6Al–4V–2B4C coated AISI 1040 steel substrates is certainly defined not only in terms of the film thickness but also in terms of the indentation depth. The indentation depth on the film strongly affects the hardness of the Ti–6Al–4V–2B4C coated AISI 1040 steel
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Fig. 8 – Force–displacement curve for different coating time (a) 0.5 h and (b) 1.0 h. substrates, and it probably influences the mechanical behaviour such as the load capacity and the wear resistance of realworld applications. It can be seen that the nano hardness of the Ti–6Al–4V–2B4C coated AISI 1040 steel substrates decreases when increasing the maximum indentation depth. The higher nano hardness of the composite coatings is due to the finer surface morphology, more compact structure and also as a result of homogeneously distribution of nano B4C particles in the coating. The finer surface can increase the load carrying areas and increase the indentation resistance of the Ti–6Al– 4V–2B4C coating. On the other hand, the nano B4C particles possess higher nano hardness, which can hinder the migration of dislocations during the deformation. Adhesive force measurements were carried out for Ti–6Al– 4V–2B4C coating using the ‘‘force calibration mode’’. Fig. 8 shows an example of a force distance curve obtained for Ti– 6Al–4V–2B4C coating. The indicated point A is called ‘‘pull on’’ point because the cantilever suddenly springs in contact with the sample because of short range attractive forces. The intender extends until the cantilever attains the preset trigger deflection value. The cantilever deflects beyond the free air deflection point because of adhesive forces, the cantilever elastic force equals the adhesive force and the just after this point, the cantilever give way back to free air deflection value. The point where the cantilever force equals the adhesive force is termed as 'pull off' point since the cantilever pulls off from the sample at this point.
3.4. Effect of specific wear rate on Ti–6Al–4V–2B4C coated AISI 1040 steel Fig. 9 shows the scattered variation of specific wear rate as a function of reinforcement and applied load for both 0.5 h and 1 h coating with Ti–6Al–4V–2B4C on AISI 1040 steel. It shows that as the sliding increases, the specific wear rate of both the coatings was increased. The specific wear rate of the 0.5 h coating is more than that of the 1 h coating for all applied normal loads. Also, it is noticed that with increase of normal
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load value in the contact zone there is an increase of specific wear rate value, which is accordant to theoretical forms. The lower specific wear rates in coating with higher amount of B4C particles can be attributed to the high hardness and good interfacial bonding on both coating. On the other hand, the coating experiences an increase in specific wear rate with increasing applied loads, indicating that B4C particles can protect the coating effectively during sliding wear. From Fig. 9 it is clear that the specific wear rate of the 3 N loads is high compared to the coating with 2 N loads. At 2 N loads, the specific wear rate of both coatings with 2% B4C are almost same. Wear resistance is defined as the reciprocal of the weight loss for a given sliding distance. The specific wear rate varied from 3.1017 104 mm3/Nm for 0.5 h coating with maximum load and sliding distance. Similarly for 1 h coating the specific wear rate was 3.5952 104 mm3/Nm [15]. Fig. 9 shows the scattered variation in specific wear rate with sliding distance and load for both coated and uncoated AISI 1040 steel. It is clear from Fig. 9 that the specific wear rate of coated steel is 2 times lower than the uncoated steel. Further uncoated steel the maximum specific wear rate of produces 4.9952 104 mm3/Nm. The Ti–6Al–4V–2B4C coated AISI 1040 steel exhibits specific wear rate values up to 2 times lower values than that of the uncoated AISI 1040 steel. The specific wear rate of uncoated AISI 1040 steel was discussed by Ugur Sen [6] which produces higher specific wear rate when compared with Ti–6Al–4V–2B4C coated AISI 1040 steel. The specific wear rate decreases as the amount of B4C reinforcement increases for all applied normal loads but its effect is more predominant at lower loads. At 3 N loads the specific wear rate is almost independent of the B4C amount. It is clearly stated that this parameter brings out the development in inherent wear resistance of the coating with increase in the amount of B4C reinforcement. Three experimental trials were conducted on the AISI 1040 coated steel for the coating time (0.5 and 1 h) and uncoated steel for two loads with four sliding distances to determine the SWR. Fig. 9 shows the scattered diagram against specific wear rate of Ti–6Al–4V–2B4C coated AISI 1040 steel with sliding distance, coating time and load for all the 3 replications of coated and uncoated AISI 1040 steel. The averages of three trials of each sample are indicted by a smooth line. Similarly, Fig. 10 shows the scattered variation of specific wear rate with varying sliding velocity and load for each sample. It is further observed that the specific wear rate increases with the increase in sliding velocity for all samples. This is due to the fact that frictional heat generated between the contact surfaces of disc and steel ball was more. Moreover duration of wear test is same (120 s) for all sliding velocities thus the sliding length varies based on sliding velocity of samples. Three experimental trials were done on the AISI 1040 coated steel for coating time (0.5 and 1 h) and uncoated steel for two loads with four sliding velocity to determine the SWR. Fig. 10 shows the specific wear rate of Ti–6Al–4V–2B4C coated AISI 1040 steel against sliding velocity, coating time and load for all the 3 replications of coated and uncoated AISI 1040 steel. Curve fitting technique was applied to develop the best fit, second order polynomial equations for each coating along with its regression co-efficient value recorded in Tables 2 and 3. The
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Fig. 9 – Specific wear rate of Ti–6Al–4V–2B4C coated AISI 1040 steel on sliding distance for all the 3 replications.
regression coefficient is used for defining the residuals of each experimental run. The scattered points of specific wear rate indicate that the regression coefficient is a best fit for the experimental values with R2 value < 1.
3.5.
Effect of friction coefficient
The coefficient of friction of Ti–6Al–4V–2B4C coated and uncoated samples were presented in Fig. 11. The values of the coefficient of friction correspond to dry sliding conditions, and are related with the hardness values. Due to the increase of coating time and coating thickness the hardness of the AISI 1040 steel was increased. Furthermore the hardness increases with decrease in coefficient of friction. The coefficients of friction obtained for uncoated AISI 1040 steel is 0.58 for 0.5 h coating and 0.65 for 1 h coating against 2 N and 3 N. The coefficient of friction of Ti–6Al–4V–2B4C coated AISI 1040 steel is decreased by 75% when compared with uncoated steel. Coefficient of friction of NbC coated AISI 1040 steel varies from 0.40-0.55 as explained by Saduman Sen [2]. The coefficients of friction of Ti–6Al–4V–2B4C coated AISI 1040 steel ranges between 0.43 and 0.48 against 0.5 h coatings, 0.42 and 0.45 against 1 h coatings with normal load of 2 N and 3 N respectively [16]. It is clearly shows that the coefficient of friction is decreased with increase in coating thickness. The value of coefficient of friction obtained in our study was lower
due to the several reasons: contact geometry, combination load and speed, surface roughness, counter-body material, etc. Ti–6Al–4V–2B4C coated AISI 1040steel suffered a lesser amount of severe wear since it had higher wear resistance due to its high hardness. Fig. 11 shows the variation of coefficient of friction with various loads and coating time. While the Ti–6Al– 4V–2B4C coated AISI 1040 steel surface and counter-body (E52100 steel ball) were in relative motion, the frictional heat developed between the surfaces were continuous because there was no time to dissipate the heat. Due to that reason the coefficient of friction was not stabilized.
3.6.
Analysis of wear mechanism
The wear rates of Ti–6Al–4V–2B4C coatings are influenced by many parameters. Wear mechanism is one of the parameters that have an effect on the evolution of the AISI 1040 steel coated Ti–6Al–4V–2B4C wear process. Adhesion, oxidation, delamination and micro-abrasive wear mechanisms can occur during wear test. Fig. 12 presents SEM image of the worn surface of Ti– 6Al–4V–2B4C coating. It is well known that the wear resistance of coating is dependent on the load, working conditions and the nature of boding between substrate and coating. The Ti–6Al– 4V–2B4C coated AISI 1040 steel shows a decreased specific wear rate; due to the B4C particles present in the film can protect the coating effectively. The Ti–6Al–4V–2B4C coated AISI 1040 steel
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Fig. 10 – Specific wear rate of Ti–6Al–4V–2B4C coated AISI 1040 steel on sliding velocity for all the 3 replications.
showed the lowest wear and coefficient of friction values. In addition, the lowest wear of the counter-body (E-52100 steel ball) occurred when it was in the contact with this coating. The wear rate of counter body was negligible compared to that of coated specimen. This clearly shows that the hardness value of the coating is higher. The worn surface of coating illustrate with mixed regions of delamination and micro-abrasive wear. The surface expose smoother wear surface with reduced wear and delamination. It is noted that the worn surface of the AISI 1040
Table 2 – Curve fitting results: specific wear rate vs sliding velocity. Coating time (h)
Load (N)
Polynomial equation – second order
R2
Uncoated Uncoated 0.5 0.5 1.0 1.0
2 3 2 3 2 3
y = 0.4755x2 + 1.0163x 0.0313 y = 0.5778x2 + 1.1763x 0.1428 y = 0.4755x2 + 0.8941x 0.0634 y = 0.5778x2 + 1.1458x 0.2359 y = 1.1544x2 + 2.1032x 0.6568 y = 0.7300x2 + 1.3963x 0.4311
0.9970 0.9986 0.9629 0.9922 0.9933 0.9907
steel displays signs of abrasive and adhesion wear as well as severe plastic deformation on the coated surface. Wear scars of the coated samples was observed by SEM, in order to identify the microstructural behaviour and leading wear mechanisms of the coated samples. Fig. 12(a–b) shows the SEM image of wear track of 0.5 h and 1 h coated AISI 1040 steel with maximum of 3 N load. Fig. 12(a) indicates the cracks and pulled out particles corresponding to weaker regions in the coatings. Wear track of the disc contains oxide layers with cracks. The oxide layers were formed due to the increase in sliding speed, which may cause an increase in temperature of the contact area between Ti–6Al–4V–2B4C coated AISI 1040 steel and counter body. Oxidation takes place on the contact area due to increase in temperature on the wear track. Fig. 12(b) shows the increase in amount of delamination of the coated AISI 1040 steel on the wear track with increase in
Table 3 – Curve fitting results: specific wear rate vs sliding distance. Coating time (h)
Load (N)
Polynomial equation – second order
R2
Uncoated Uncoated 0.5 0.5 1.0 1.0
2 3 2 3 2 3
y = 3E05x2 + 0.0085x 0.0317 y = 4E05x2 + 0.0098x 0.1432 y = 3E05x2 + 0.0075x 0.0636 y = 4E05x2 + 0.0096x 0.2362 y = 8E05x2 + 0.0185x 0.6919 y = 5E05x2 + 0.0116x 0.4315
0.9970 0.9986 0.9628 0.9921 0.9933 0.9907
Fig. 11 – Coefficient of friction of tested samples.
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Fig. 12 – SEM image of the wear track of coated samples (a) 0.5 h and (b) 1.0 h.
load. Worn material of the coating is accumulated over the wear track; this accumulated worn material caused fluctuation of the penetration depth value during the wear test [2,6]. The Energy Dispersive Spectrum (EDS) analysis of the worn surfaces of Ti–6Al–4V–2B4C coated AISI 1040 steel is shown in Fig. 13. Through EDS analysis, it is confirmed that the wear tracks mainly consists of Ti, Al, V, B, C, Si, Mn, S, P, O, and Fe. The Ti peak in the wear track was identified with high intensity in the EDS analysis. EDS analysis shows the presence of oxide layer in the wear track. The oxide layers were formed due to increase in temperature on the wear track.
3.7.
the sliding wear test was calculated for various sliding velocity and load. Tf ¼
pffiffiffi mV pFn Py 8k
(6)
Flash temperature
This present section deals about the estimation of flash temperature generated during sliding wear of the coating. Flash temperature is the term mentioned as the maximum temperature which is generated during sliding wear test and is explained by Suresh Babu Pitchuka [17]. The flash temperatures of the coatings were estimated using Archard's equation for the material mentioned in Eq. (6) [18]. Flash temperature of
Fig. 13 – EDS of worn surface of Ti–6Al–4V–2B4C coated AISI 1040 steel.
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Table 4 – Flash temperature of various samples. Coating time (h) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
Fn (N)
COF (m)
V (m/s)
Tf (8C)
2 2 2 2 3 3 3 3 2 2 2 2 3 3 3 3
0.43 0.43 0.43 0.43 0.48 0.48 0.48 0.48 0.42 0.42 0.42 0.42 0.45 0.45 0.45 0.45
0.52 0.65 0.79 0.92 0.52 0.65 0.79 0.92 0.52 0.65 0.79 0.92 0.52 0.65 0.79 0.92
27.6 34.6 41.5 48.4 37.8 47.3 56.7 66.2 29.0 33.8 40.5 47.3 35.4 44.3 53.2 62.1
where Tf = flash temperature (8C), m = coefficient of friction, V = velocity (m/s), Fn = normal force (N), Py = yield strength (Pa), and k = thermal conductivity (W/m8C). Table 4 shows the flash temperature of the coated samples with various parameters. The wear tests were performed at room temperature condition (26 8C) and the temperature was raised during the sliding. The thermal conductivity and yield strength of the AISI 1040 steel are 51.9 W/m8C and 415 MPa respectively. Friction at the contact surface will result in heat generation, which subsequently results in temperature increase (flash temperature). Hence it is important to characterize the flash temperatures during sliding. The temperature rise is started from 27.6 8C to a maximum of 48.4 8C for 0.5 h coating time with a normal load of 2 N. The flash temperature of the coating varies from 37.8 8C to 66.2 8C with 0.5 h coating time, which is the highest flash temperature. The better thermal conductivity of the substrate, creating it relatively easier to dissipate the heat through the layer, thus resulting is lower surface flash temperature. The value of flash temperature was calculated as the range between 29 8C and 47.3 8C for 1 h coating with 2 N load. The maximum of flash temperature was obtained as 62.1 8C and the minimum of 35.4 8C for 1 h coating time with 3 N load. The above results clearly show the impact of flash temperature. It is noted that the flash temperature of the coating was increased due to increasing load with sliding velocity and due to increase in surface roughness.
4.
Conclusions
This work has studied the surface morphology, friction, wear behaviour and flash temperature of the Ti–6Al–4V–2B4C coating and the following conclusions are noted. Ti–6Al–4V–2B4C coating were successfully deposited on AISI 1040 steel by magnetron sputtering method of various coating thickness. The prepared Ti–6Al–4V–2B4C coatings were characterized by AFM and XRD. The results show Ti–6Al–4V–2B4C coatings reveal dense uniform structure.
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The coefficient of friction of Ti–6Al–4V–2B4C coated AISI 1040 steel ranges between 0.43 and 0.48 against 0.5 h coatings, 0.42 and 0.45 against 1 h coatings. The coefficients of friction between steel ball and Ti–6Al–4V– 2B4C coated AISI 1040 steel were increased for all combinations with the increase in load. The flash temperature of the coatings has been estimated for various loads and sliding distances. A higher flash temperature of 48.4 8C and 66.2 8C has been estimated for 0.5 h coatings against 2 N and 3 N normal load respectively. The maximum flash temperature of 47.3 8C and 62.1 8C has been estimated for 1 h coatings against 2 N and 3 N normal load is noticed.
references
[1] P.J. Kelly, R.D. Arnell, Magnetron sputtering: a review of recent developments and applications, Vacuum 56 (2000) 159–172. [2] S. Sen, U. Sen, Sliding wear behavior of niobium carbide coated AISI 1040 steel, Wear 264 (2008) 219–225. [3] A.V. Stanishevsky, M.J. Walock, Y. Zou, L. Imhoff, A. Zairi, C. Nouveau, Growth of WC-Cr-N and WC-Al-N coatings in a RF-magnetron sputtering process, Vacuum 90 (2013) 129– 134. [4] N.V. Gavrilov, V.V. Ivanov, A.V. Nikonov, Investigations of Mn–Co–O and Mn–Co–Y–O coatings deposited by the magnetron sputtering on ferritic stainless steels, Surface & Coatings Technology 206 (2011) 1252–1258. [5] H. Pengfei, J. Bailing, Study on tribological property of CrCN coating based on magnetron sputtering plating technique, Vacuum 85 (2011) 994–998. [6] U. Sen, Wear properties of niobium carbide coatings performed by pack method on AISI 1040 steel, Thin Solid Films 483 (2005) 152–157. [7] L. Benea, S.-B. Başa, E. Danaila, N. Caron, O. Raquet, P. Ponthiaux, J.-P. Celis, Fretting and wear behaviors of Ni/nanoWC composite coatings in dry and wet conditions, Materials & Design 65 (2015) 550–558. [8] A. Cavasin, T. Brzezinski, S. Grenier, M. Smagorinski, W and B4C coatings for nuclear fusion reactors, Advanced Materials & Processes 167 (1998) 957–961. [9] R. Harichandran, N. Selvakumar, Effect of nano/micro B4C particles on the mechanical properties of aluminium metal matrix composites fabricated by ultrasonic cavitationassisted solidification process, Archives of Civil and Mechanical Engineering 16 (1) (2016) 147–158. [10] W. Chen, Y. Yamamoto, W.H. Peter, S.B. Gorti, A.S. Sabau, M. B. Clark, S.D. Nunn, J.O. Kiggans, C.A. Blue, J.C. Williams, B. Fuller, K. Akhtar, Cold compaction study of Armstrong process Ti–6Al–4V powders, Powder Technology 214 (2011) 194–199. [11] S.C. Vettivel, N. Selvakumar, N. Leema, Experimental and prediction of sintered Cu–W composite by using artificial neural networks, Materials and Design 45 (2013) 323–335. [12] M. Wang, T. Toihara, M. Sakurai, W. Kurosaka, S. Miyake, Surface morphology and tribological properties of DC sputtered nanoscale multilayered TiAlN/CNx coatings, Tribology International 73 (2014) 36–46. [13] K.W. Xu, G.L. Hou, B.C. Hendrix, J.W. He, Y. Sun, S. Zheng, A. Bloyce, T. Bell, Prediction of nanoindentation hardness profile from a load–displacement curve, Journal of Materials Research 13 (12) (1998) 3519–3526.
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[14] C.-H. Tasi, Y.-C. Tseng, S.-R. Jian, Y.-Y. Liao, C.-M. Lin, P.-F. Yang, D.-L. Chen, H.-J. Chen, C.-W. Luo, J.-Y. Juang, Nanomechanical properties of Bi2Te3 thin films by nanoindentation, Journal of Alloys and Compounds 619 (2015) 834–838. [15] M. Yandouzi, A.J. Bottger, R.W.A. Hendrikx, M. Brochu, P. Richer, A. Charest, B. Jodoin, Microstructure and mechanical properties of B4C reinforced Al-based matrix composite coatings deposited by CGDS and PGDS processes, Surface & Coatings Technology 205 (2010) 2234–2246.
[16] Y.-S. Yang, T.-P. Cho, H.-W. Ye, The effect of deposition parameters on the mechanical properties of Cr–C–N coatings, Surface & Coatings Technology 259 (2014) 141–145. [17] S.B. Pitchuka, B. Boesl, C. Zhang, D. Lahiri, Dry sliding wear behavior of cold sprayed aluminum amorphous/ nanocrystalline alloy coatings, Surface & Coatings Technology 238 (2014) 118–125. [18] H.E. Maupin, R.D. Wilson, J.A. Hawk, Wear deformation of ordered Fe-Al intermetallic alloys, Wear 162–164 (1993) 432–440.
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Original Research Article
Microstructure, surface topography and sliding wear behaviour of titanium based coating on AISI 1040 steel by magnetron sputtering Selvakumar N a,1, Malkiya Rasalin Prince R b,* a
Centre for Nano Science & Technology, Department of Mechanical Engineering, Mepco Schlenk Engineering College, Sivakasi 626 005, Tamil Nadu, India b Department of Mechanical Engineering, Bethlahem Institute of Engineering, Karungal, Tamilnadu, India
article info
abstract
Article history:
In the present study, 2% B4C reinforced with Ti–6Al–4V composite coatings on AISI 1040 steel
Received 20 May 2016
plates were coated using magnetron sputtering. The microstructure and surface morphol-
Accepted 16 October 2016
ogies of the coated specimen were analyzed using SEM, XRD, EDS and AFM. The uniform
Available online
coating thickness of 75 nm and 110 nm on smooth surfaces have been obtained for 0.5 h and 1 h coating time respectively. Under the normal load of 2 N and 3 N, Ti–Al–V–B4C coatings
Keywords:
wear analysis were performed and resulted in excellent wear rate with lower coefficient of
Magnetron sputtering
friction. Ti–Al–V–B4C thin film shows the nano hardness value of 7.2 GPa and 9.7 GPa for 0.5 h
Ball on disc
and 1 h coating time and elastic modulus of 204 GPa. The surface roughness (Ra) of 0.5 h and
Flash temperature
1 h coating are 3.393 nm and 17.433 nm respectively. The addition of B4C particles reinforced
AISI 1040 steel
Ti–Al–V composite coatings showed enhanced nano hardness and improved the wear
Ti–6Al–4V–2B4C
resistance with decrease in the coefficient of friction. The amount of heat generated during wear test has been calculated. Ti–Al–V–B4C composite coatings were exposed to lowest wear rates among all loading conditions and thus signifying that it could be a promising alternative to other hard coatings. # 2016 Politechnika Wrocławska. Published by Elsevier Sp. z o.o. All rights reserved.
1.
Introduction
Medium carbon steel is the major constituent to fabricate components in engineering, mining, construction and agricultural field due to its better strength and higher hardness. Most of the sliding materials mainly failed due to wear, so wearable
materials have always been the best topic for the respective researchers. The uses of innovative coatings play an important role for the production of thin films with outstanding properties. In particular, the manufacturing of Ti–Al–V–B4C coating is a promising way to achieve thin films with outstanding properties. The most noted hardness of B4C is its excellent resistance to wear. Magnetron sputtering has
* Corresponding author. E-mail addresses: [email protected] (S. N), [email protected] (M.R.P. R). 1 Fax: +91 04562 2235111. http://dx.doi.org/10.1016/j.acme.2016.10.005 1644-9665/# 2016 Politechnika Wrocławska. Published by Elsevier Sp. z o.o. All rights reserved.
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become the choice for the deposition of a wide-range of industrially important hard coatings. Titanium Grade-5 (Ti–6Al–4V) alloy is mostly used in aerospace, medical and aircraft industries due to its unique strength-to-weight ratio. Carbide and nitride coatings improve the strength, hardness and wear resistance of steel. Boron carbide coating has found variety of applications such as plasma-faced components in fusion reactors, electromagnetic radiation field, coatings on nozzles, high precision tooling dies. Magnetron sputtering is an enormously adaptable technique for the deposition of highquality with well-adhered films [1]. The development of NbC coating on AISI 1040 steel exhibited low coefficient of friction, higher wear rate, compact, smooth, porosity free and homogeneous [2]. Hard coating with nitride and carbide is a general route for developing the wear resistance of metals. In general nitrides and carbides exhibit low coefficient of friction, excellent wear resistance and higher hardness [3]. Surface hardness of the steel has been improved via hard coatings and a mixed phase of film has been obtained. Among the ferrous materials, the AISI 1040 steel is the most popular material for industries [4]. A pin-on-disc experiment shows that the CrCN coatings exhibit lower friction coefficient and remarkable wear resistance better than CrN coating. [5]. Wear behaviour of TiAlN/ CNx coatings on cemented carbide tool steel were improved, the coefficient friction and wear depth of the coatings were reduced [6]. Ni/WC nanocomposite coatings exhibit improved nanohardness and better resistance to wear compared with pure Ni coatings. The nanoidentation was found that Ni/nanoWC composite coatings exhibit enhanced nanohardness as compared with pure nickel coatings [7]. Boron carbide coating has found a wide range of applications, including fusion reactor components, coating on nozzles, high precision tooling dies, radiation shields due to its superior physical and mechanical properties. B4C coated steel substrate shows high hardness and it can be used as inertial confinement in fusion reactors [8]. However, in order to afford adequate wear, the
coating need to be uniform, adhesive, pore free and wear resistant. Therefore, in the present study, Ti–Al–V–2B4C coatings were selected as wear resistive coatings for AISI 1040 steels in order to develop its wear resistance.
2.
Materials and experimental details
2.1.
Materials
Titanium alloy Ti–6Al–4V has notable mechanical properties at room temperature, having better tensile strength. Ti–6Al–4V has exceptional resistance to corrosion in most natural and various industrial processing environments. Boron carbide is an extremely hardest ceramic material and ranking third behind diamond and cubic boron nitride. The chemical composition of AISI 1040 steel is C 0.35-0.44%, Si 0.20%, Mn 0.75%, S 0.05%, P 0.04% and balance Fe [9].
2.2.
XRD analysis
Crystal structure and orientation of the Ti–6Al–4V–2B4C coating were studied by X-ray diffractometer with monochromated Cu Ka radiation (K = 1.54060 Å) at 60 kV over the range of 2u = 20–808 with a step size of 0.0170 and a step time of 3.1750 s. The phase purity and grain size were determined by XRD analysis.
2.3.
Target and substrate preparation
The powders form of Ti, Al, V and B4C were used as target material. The target was prepared with Ti–6Al–4V–2B4C. The powders were milled and mixed properly via mechanical milling under argon atmosphere. This mechanical milling process provided homogeneous mixture of the composites for formulating the target. Fig. 1 shows the scanning electron microscopic image of the pre compacted powders. All the pre
Fig. 1 – SEM image of pre compacted Ti–6Al–4V–2B4C powders.
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on the holder, by maintaining a target to substrate distance of 60 mm. Sputtering chamber was evacuated to 1 105 N/m2 and the substrates were blasted using argon ion (Ar+). The substrate coating temperature was maintained at about 100 20 8C. The coating time for all specimens was fixed as 0.5 h, 1 h respectively. For all the coatings the sputtering gas pressure is kept in the range of (Ar) 0.001 to 0.1 N/m2. Ti–6Al– 4V–2B4C adhesion layers were deposited on the substrate uniformly.
2.5.
Fig. 2 – EDS pattern of Ti–6Al–4V–2B4C target.
compacted powder particles were in irregular, angular shape with rough surfaces, in order to study the microstructure of the Ti, Al, V, B4C powders before preparing target. Chen et al. [10] explained the method of achieving 75% relative density of compact for Ti–Al–V with a compaction pressure of 700 MPa. The green compact of Ti–6Al–4V–2B4C was uniaxially compressed by compression testing machine. Total required amount of Ti, Al, V and B4C milled powders were pressed uniaxially with a pressure of 650 MPa at room temperature. The green compact was sintered with an inert gas circulated electric muffle furnace at 950 8C for a holding period of 1 h. To avoid oxidization, the green compacts in the beginning were protected with inert argon atmosphere in the furnace. After that the sintered target was brought into room temperature under furnace cooling conditions. The target with a diameter of 54 mm and thickness of 3 mm was obtained. Fig. 2 shows the Energy Dispersive Spectrum (EDS) analysis of Ti–6Al–4V–2B4C target. EDS analysis confirms the presence of Ti, Al, V, B and C. The elemental peak of Ti was identified as the major peak with high intensity. The other elements like Al, V, B and C were identified with minor peaks. In EDS analysis, no oxide peak was observed. EDS analysis suggests that B and C particles in the target were stable during sintering time and no intermetallic layer were found in the target. AISI 1040 steel plates were used as the substrate for the required coating. AISI 1040 steel plate samples of 60 mm diameter and 3 mm thickness were prepared by 350 grit waterproof silicon carbide grinding wheels and then by 60, 80, 120, 220, 320 grade Al2O3 waterproof papers to get a smooth mirror polishing surface. After that, the organic impurities present in the surface were cleaned with n-propanol and acetone. Then the cleaned samples were loaded in the sputtering chamber for coating. The loaded substrates were further cleaned by argon ion bombardment for achieving better bonding of coatings.
2.4.
AFM analysis
AFM is suitable for obtaining three-dimensional topographic information of thin film coatings for structural analysis on the nano scale. The topography of the coating is analyzed with AFM (XE 70, Park Systems–S. Korea). The surface roughness and particle size are examined using AFM analysis. AFM nano indentation was also used to study the mechanical properties of the coatings with a variation of loads. Analysis of surface quality and roughness of Ti–6Al–4V–2B4C thin film were carried out using AFM method. This was verified by performing force measurements on underlying AISI 1040 steel substrate at a sufficiently small loading force to ensure little indentation.
2.6.
Wear test
After coating of Ti–6Al–4V–2B4C on AISI 1040 substrate, the dry sliding wear test was conducted using a ball on disc wear tester. Fig. 3 shows the ball on disc arrangement that was used for the wear test. The contact steel ball was cleaned with acetone for better surface contact between ball and disc. The steel ball of 10 mm in diameter with a hardness value of 450 VHN was used for wear test and it is fixed in the holder. The wear test parameters were noted and given in Table 1. Wear test was conducted on the coated specimen by applying load on steel ball with varying track radius of 20 mm, 25 mm, 30 mm and 35 mm respectively. Wear tests were carried out with two normal loads (2 N, 3 N) and different sliding velocities (0.52, 0.65, 0.79 and 0.92 m/s). The sliding velocity was calculated from the track radius and sliding speed. The wear testing was carried out with a fixed time of 2 min for all the tests. After each test the wear loss of the coated disc was weighed using a sensitive electronic balance with an accuracy of 0.01 mg to find out the weight loss. The weight loss was converted into volume loss. The wear rate was calculated from
Deposition of Ti–Al–V–2B4C films
Sputter deposition technique is a physical vapour deposition method for preparing thin films using a DC magnetron sputtering process. These methods consist of emitting material from a target that is a source (Ti–6Al–4V–2B4C) onto a substrate (AISI 1040). The target and substrate were mounted
Fig. 3 – Schematic diagram of ball-on-disc wear testing machine.
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Table 1 – Wear and friction test parameters of Ti–6Al–4V– 2B4C coated sample. Parameters
Values
Applied load (N) No. of trail for each samples Velocity (m/s) Speed of the disc (rpm) Wear track diameter (mm) Working temperature (8C) Relative humidity (%) Test duration (s) Test balls Environment
2, 3 3 0.52, 0.65, 0.79 and 0.92 500 20, 25, 30 and 35 26 65 120 Steel Dry air
the wear volume and the sliding distance. Frictional force was measured from the recorded graph during wear test. The wear volume, wear rate, specific wear rate and coefficient of friction were calculated by using the following Eqs. (1)–(4) [11].
Wear loss Density
(1)
Wear volume Sliding distance
(2)
Wear volume ¼
Wear rate ¼
Specific wear rate ¼
Wear volume Load Sliding distance
(3)
Frictional force Applied load
(4)
Coefficient of friction ¼
3.
Results and discussion
3.1.
XRD analysis
Fig. 4 shows the XRD pattern with the peaks Ti, Al, V and B4C. The elemental confirmation was made by XRD study and Ti (JCPDS 89-2762) exhibited a peak at 35.18, indicating a strong (1 0 0) orientation in the coating. Ti peaks with 2u values of
Fig. 4 – XRD pattern of the Ti–6Al–4V–2B4C coated AISI 1040 steel.
40.28, 62.98, 70.68, 76.18 and 77.38 belong to the crystal planes of (1 0 1), (1 1 0), (1 0 3), (1 1 2) and (2 0 1) respectively. Aluminium peaks in the plane (1 1 1), (2 0 0) and (3 1 1) were confirmed using the JCPDS file no. 89-4037 with 2u values of 38.48 and 44.88. It can be matched with the JCPDS file no. 22-1058 for vanadium with characteristic peaks in the plane of (1 1 0) corresponding 2u value of 42.18. The presence of boron carbide particles in the coating were represented by the characteristic peaks in the plane of (2 0 0), (2 1 4) and (0 2 7) with 2u values of 53.48, 58.88 and 65.18. The results matched very well with the JCPDS file No. 75-0424. It is noted that no oxide peak was observed in the XRD analysis. This suggests that no intermetallic layer were found during coating and B4C particles were stable during coating time. XRD patterns confirm the presence of B4C in the coating. It was observed that the peaks of Ti, Al, V and B4C were wider. The broadness of the peaks deals with the size of the particles and the randomness with which they are orientated. Hence from this analysis it is clear that the particles present in the coatings are in nano scale. Fig. 5 shows the Energy Dispersive Spectrum (EDS) analysis of Ti–6Al–4V–2B4C coating. From Fig. 5, the various elements in the coating were identified through different peaks. The various elements identified in the coating are Ti, Al, V, B, C, Si, Mn, S, P and Fe. The elements of substrate are shown in Fig. 5, the presence of C, Si, Mn, S, P and Fe confirms the chemical composition of the substrate. No oxide peak was observed in the EDS analysis.
3.2.
AFM analysis
AFM profiles in Figs. 6 and 7 demonstrate the topography of Ti– 6Al–4V–2B4C coated AISI 1040 steel substrate. The thickness of coated Ti–6Al–4V–2B4C thin films was evaluated by AFM method, the overall thickness of the coating was determined around 75 nm throughout the coating for 0.5 h coating time. Fig. 6(a) displays two-dimensional (2D) AFM images of Ti–6Al– 4V–2B4C films with 0.5 h coating duration. The AFM image reveals the waviness surface texture of Ti–6Al–4V–2B4C thin films. Waviness is the measure of extensively spaced component in the surface pattern and is associated to roughness. The average surface roughness Ra on the coating was 3.946– 3.393 nm. The average distance between the highest peak and bottom most valley (Rz) is calculated as 24.451 nm. The average
Fig. 5 – EDS pattern of Ti–6Al–4V–2B4C coated AISI 1040 steel.
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Fig. 6 – Topography of 0.5 h coated Ti–6Al–4V–2B4C film (a) 2D and (b) 3D.
mean square Rq value of the coating is obtained as 4.529 nm. It is noted that the surface roughness of Ti–6Al–4V–2B4C coating is lower than that of the TiAlN/CNx coatings [12]. Fig. 6(b) shows three-dimensional (3D) AFM images of Ti– 6Al–4V–2B4C films. The surface of the coatings is relatively smooth and the surface looks like valley and hill shape. The surface of the coatings and film growth were in ordered manner. The ‘‘valley’’ section is comparatively smooth, while the ‘‘hill’’ sector encloses many crystal-like structures that exhibit certain orientations. It is understood that reduction in grain size may moderate the roughness of the film surface and thus the wear behaviour of the coating was enriched. Fig. 7(a) shows the two-dimensional (2D) image of the Ti– 6Al–4V–2B4C coatings with 1 h coating time. The coating thickness of 110 nm has been obtained for 1 h coating duration. The surface roughness Ra of the Ti–6Al–4V–2B4C coating was 15.749–17.433 nm. The average distance between the highest peak and lowest valley, Rz, is calculated as 82.564 nm. The Rq value of the coating is obtained as 20.212 nm. Due to the increase in coating thickness and constant substrate temperature, the value of surface roughness improved with coating time. This is due to the more
deposition time that admits the formation of coarse structures which leads to an increase in surface roughness. Fig. 7(b) shows three-dimensional (3D) AFM images of Ti– 6Al–4V–2B4C films. The surface looks like a honeycomb structure. It is clearly noted that the surface roughness of the coated surface has been enriched. The maximum grain size of the coatings was observed that of 25 nm and the average grain size of the coatings was observed that of 4 nm. The overall height of the coating was detected around 25 nm throughout the coating. The value of the peak position was measured which is approximately 74 nm. Both the coatings were having homogeneous microstructure observed by AFM. The Ti–6Al–4V–2B4C thin film coatings reveal similar dense, homogeneous microstructure even though the grain size of the coating increasing with increasing the coating time.
3.3. Effect of hardness on Ti–6Al–4V–2B4C coated AISI 1040 steel AFM nano indention is an alternative technique to evaluate the mechanical properties of thin film coatings on a very small scale. Even though thin film coatings with coating thickness
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Fig. 7 – Topography of 1 h coated Ti–6Al–4V–2B4C film (a) 2D and (b) 3D.
lesser than 5 nm can be calculated. Nano technique allows the user to measure the nanoscale hardness of thin film coatings. Nano indentation technique consists of 3 phases such as loading, holding and unloading processes. The contact mode AFM probe can be applied to obtain the image. The penetration of the indentation is measured from the AFM image. During indentation, a force–displacement (F-D) curve has been obtained and nano hardness of the coating has been calculated from F-D curve. At first the indentation process progresses, during the indentation amount of force required for indentation gradually increases which is specified by the red line. The maximum applying load as 4 nN, after applying the specified load the tip freely penetrates the coating which is displayed by the inclined blue line. After that, the tip is slowly removed from the coating. The F-D curve of the coating has been obtained for the load input of 4 nN. From these F-D curves, the nano hardness (H) of the coating can be calculated by using the formula (5) [13]. H¼
P 24:5ðhc Þ2
(5)
where P – maximum applied load, hc – penetration depth. Fig. 8(a–b) represents the nanoindentation force– displacement curve of 0.5 h coating and 1 h coating time.
Ti–6Al–4V–2B4C coated AISI 1040 steel shows the maximum elastic modulus of 204 GPa. The calculated value of hardness for the Ti–6Al–4V–2B4C coating under 0.5 h and 1 h coating time is 7.2 GPa and 9.7 GPa respectively [14]. Initially the hardness of the coating increased because of small penetration depth, which is generally recognized as the conversion between only elastic to elastic/plastic contact takes place and at this stage the obtained mean contact pressure does not exactly denote the actual hardness of the coating. The mean interaction pressure represents the hardness of the coating only under the condition of a fully developed plastic zone. When the coating has no plastic zone, or formed only partially plastic zone, the mean contact pressure is less than the hardness of the coating. The hardness value of the coating initially rises with the depth of penetration to a maximum value and then gradually decreases to a constant value. During this stage, the value of the hardness decreases and reaches a constant value, which could be observed as true hardness of the Ti–6Al–4V– 2B4C coating. The hardness behaviour of the Ti–6Al–4V–2B4C coated AISI 1040 steel substrates is certainly defined not only in terms of the film thickness but also in terms of the indentation depth. The indentation depth on the film strongly affects the hardness of the Ti–6Al–4V–2B4C coated AISI 1040 steel
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Fig. 8 – Force–displacement curve for different coating time (a) 0.5 h and (b) 1.0 h. substrates, and it probably influences the mechanical behaviour such as the load capacity and the wear resistance of realworld applications. It can be seen that the nano hardness of the Ti–6Al–4V–2B4C coated AISI 1040 steel substrates decreases when increasing the maximum indentation depth. The higher nano hardness of the composite coatings is due to the finer surface morphology, more compact structure and also as a result of homogeneously distribution of nano B4C particles in the coating. The finer surface can increase the load carrying areas and increase the indentation resistance of the Ti–6Al– 4V–2B4C coating. On the other hand, the nano B4C particles possess higher nano hardness, which can hinder the migration of dislocations during the deformation. Adhesive force measurements were carried out for Ti–6Al– 4V–2B4C coating using the ‘‘force calibration mode’’. Fig. 8 shows an example of a force distance curve obtained for Ti– 6Al–4V–2B4C coating. The indicated point A is called ‘‘pull on’’ point because the cantilever suddenly springs in contact with the sample because of short range attractive forces. The intender extends until the cantilever attains the preset trigger deflection value. The cantilever deflects beyond the free air deflection point because of adhesive forces, the cantilever elastic force equals the adhesive force and the just after this point, the cantilever give way back to free air deflection value. The point where the cantilever force equals the adhesive force is termed as 'pull off' point since the cantilever pulls off from the sample at this point.
3.4. Effect of specific wear rate on Ti–6Al–4V–2B4C coated AISI 1040 steel Fig. 9 shows the scattered variation of specific wear rate as a function of reinforcement and applied load for both 0.5 h and 1 h coating with Ti–6Al–4V–2B4C on AISI 1040 steel. It shows that as the sliding increases, the specific wear rate of both the coatings was increased. The specific wear rate of the 0.5 h coating is more than that of the 1 h coating for all applied normal loads. Also, it is noticed that with increase of normal
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load value in the contact zone there is an increase of specific wear rate value, which is accordant to theoretical forms. The lower specific wear rates in coating with higher amount of B4C particles can be attributed to the high hardness and good interfacial bonding on both coating. On the other hand, the coating experiences an increase in specific wear rate with increasing applied loads, indicating that B4C particles can protect the coating effectively during sliding wear. From Fig. 9 it is clear that the specific wear rate of the 3 N loads is high compared to the coating with 2 N loads. At 2 N loads, the specific wear rate of both coatings with 2% B4C are almost same. Wear resistance is defined as the reciprocal of the weight loss for a given sliding distance. The specific wear rate varied from 3.1017 104 mm3/Nm for 0.5 h coating with maximum load and sliding distance. Similarly for 1 h coating the specific wear rate was 3.5952 104 mm3/Nm [15]. Fig. 9 shows the scattered variation in specific wear rate with sliding distance and load for both coated and uncoated AISI 1040 steel. It is clear from Fig. 9 that the specific wear rate of coated steel is 2 times lower than the uncoated steel. Further uncoated steel the maximum specific wear rate of produces 4.9952 104 mm3/Nm. The Ti–6Al–4V–2B4C coated AISI 1040 steel exhibits specific wear rate values up to 2 times lower values than that of the uncoated AISI 1040 steel. The specific wear rate of uncoated AISI 1040 steel was discussed by Ugur Sen [6] which produces higher specific wear rate when compared with Ti–6Al–4V–2B4C coated AISI 1040 steel. The specific wear rate decreases as the amount of B4C reinforcement increases for all applied normal loads but its effect is more predominant at lower loads. At 3 N loads the specific wear rate is almost independent of the B4C amount. It is clearly stated that this parameter brings out the development in inherent wear resistance of the coating with increase in the amount of B4C reinforcement. Three experimental trials were conducted on the AISI 1040 coated steel for the coating time (0.5 and 1 h) and uncoated steel for two loads with four sliding distances to determine the SWR. Fig. 9 shows the scattered diagram against specific wear rate of Ti–6Al–4V–2B4C coated AISI 1040 steel with sliding distance, coating time and load for all the 3 replications of coated and uncoated AISI 1040 steel. The averages of three trials of each sample are indicted by a smooth line. Similarly, Fig. 10 shows the scattered variation of specific wear rate with varying sliding velocity and load for each sample. It is further observed that the specific wear rate increases with the increase in sliding velocity for all samples. This is due to the fact that frictional heat generated between the contact surfaces of disc and steel ball was more. Moreover duration of wear test is same (120 s) for all sliding velocities thus the sliding length varies based on sliding velocity of samples. Three experimental trials were done on the AISI 1040 coated steel for coating time (0.5 and 1 h) and uncoated steel for two loads with four sliding velocity to determine the SWR. Fig. 10 shows the specific wear rate of Ti–6Al–4V–2B4C coated AISI 1040 steel against sliding velocity, coating time and load for all the 3 replications of coated and uncoated AISI 1040 steel. Curve fitting technique was applied to develop the best fit, second order polynomial equations for each coating along with its regression co-efficient value recorded in Tables 2 and 3. The
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Fig. 9 – Specific wear rate of Ti–6Al–4V–2B4C coated AISI 1040 steel on sliding distance for all the 3 replications.
regression coefficient is used for defining the residuals of each experimental run. The scattered points of specific wear rate indicate that the regression coefficient is a best fit for the experimental values with R2 value < 1.
3.5.
Effect of friction coefficient
The coefficient of friction of Ti–6Al–4V–2B4C coated and uncoated samples were presented in Fig. 11. The values of the coefficient of friction correspond to dry sliding conditions, and are related with the hardness values. Due to the increase of coating time and coating thickness the hardness of the AISI 1040 steel was increased. Furthermore the hardness increases with decrease in coefficient of friction. The coefficients of friction obtained for uncoated AISI 1040 steel is 0.58 for 0.5 h coating and 0.65 for 1 h coating against 2 N and 3 N. The coefficient of friction of Ti–6Al–4V–2B4C coated AISI 1040 steel is decreased by 75% when compared with uncoated steel. Coefficient of friction of NbC coated AISI 1040 steel varies from 0.40-0.55 as explained by Saduman Sen [2]. The coefficients of friction of Ti–6Al–4V–2B4C coated AISI 1040 steel ranges between 0.43 and 0.48 against 0.5 h coatings, 0.42 and 0.45 against 1 h coatings with normal load of 2 N and 3 N respectively [16]. It is clearly shows that the coefficient of friction is decreased with increase in coating thickness. The value of coefficient of friction obtained in our study was lower
due to the several reasons: contact geometry, combination load and speed, surface roughness, counter-body material, etc. Ti–6Al–4V–2B4C coated AISI 1040steel suffered a lesser amount of severe wear since it had higher wear resistance due to its high hardness. Fig. 11 shows the variation of coefficient of friction with various loads and coating time. While the Ti–6Al– 4V–2B4C coated AISI 1040 steel surface and counter-body (E52100 steel ball) were in relative motion, the frictional heat developed between the surfaces were continuous because there was no time to dissipate the heat. Due to that reason the coefficient of friction was not stabilized.
3.6.
Analysis of wear mechanism
The wear rates of Ti–6Al–4V–2B4C coatings are influenced by many parameters. Wear mechanism is one of the parameters that have an effect on the evolution of the AISI 1040 steel coated Ti–6Al–4V–2B4C wear process. Adhesion, oxidation, delamination and micro-abrasive wear mechanisms can occur during wear test. Fig. 12 presents SEM image of the worn surface of Ti– 6Al–4V–2B4C coating. It is well known that the wear resistance of coating is dependent on the load, working conditions and the nature of boding between substrate and coating. The Ti–6Al– 4V–2B4C coated AISI 1040 steel shows a decreased specific wear rate; due to the B4C particles present in the film can protect the coating effectively. The Ti–6Al–4V–2B4C coated AISI 1040 steel
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Fig. 10 – Specific wear rate of Ti–6Al–4V–2B4C coated AISI 1040 steel on sliding velocity for all the 3 replications.
showed the lowest wear and coefficient of friction values. In addition, the lowest wear of the counter-body (E-52100 steel ball) occurred when it was in the contact with this coating. The wear rate of counter body was negligible compared to that of coated specimen. This clearly shows that the hardness value of the coating is higher. The worn surface of coating illustrate with mixed regions of delamination and micro-abrasive wear. The surface expose smoother wear surface with reduced wear and delamination. It is noted that the worn surface of the AISI 1040
Table 2 – Curve fitting results: specific wear rate vs sliding velocity. Coating time (h)
Load (N)
Polynomial equation – second order
R2
Uncoated Uncoated 0.5 0.5 1.0 1.0
2 3 2 3 2 3
y = 0.4755x2 + 1.0163x 0.0313 y = 0.5778x2 + 1.1763x 0.1428 y = 0.4755x2 + 0.8941x 0.0634 y = 0.5778x2 + 1.1458x 0.2359 y = 1.1544x2 + 2.1032x 0.6568 y = 0.7300x2 + 1.3963x 0.4311
0.9970 0.9986 0.9629 0.9922 0.9933 0.9907
steel displays signs of abrasive and adhesion wear as well as severe plastic deformation on the coated surface. Wear scars of the coated samples was observed by SEM, in order to identify the microstructural behaviour and leading wear mechanisms of the coated samples. Fig. 12(a–b) shows the SEM image of wear track of 0.5 h and 1 h coated AISI 1040 steel with maximum of 3 N load. Fig. 12(a) indicates the cracks and pulled out particles corresponding to weaker regions in the coatings. Wear track of the disc contains oxide layers with cracks. The oxide layers were formed due to the increase in sliding speed, which may cause an increase in temperature of the contact area between Ti–6Al–4V–2B4C coated AISI 1040 steel and counter body. Oxidation takes place on the contact area due to increase in temperature on the wear track. Fig. 12(b) shows the increase in amount of delamination of the coated AISI 1040 steel on the wear track with increase in
Table 3 – Curve fitting results: specific wear rate vs sliding distance. Coating time (h)
Load (N)
Polynomial equation – second order
R2
Uncoated Uncoated 0.5 0.5 1.0 1.0
2 3 2 3 2 3
y = 3E05x2 + 0.0085x 0.0317 y = 4E05x2 + 0.0098x 0.1432 y = 3E05x2 + 0.0075x 0.0636 y = 4E05x2 + 0.0096x 0.2362 y = 8E05x2 + 0.0185x 0.6919 y = 5E05x2 + 0.0116x 0.4315
0.9970 0.9986 0.9628 0.9921 0.9933 0.9907
Fig. 11 – Coefficient of friction of tested samples.
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Fig. 12 – SEM image of the wear track of coated samples (a) 0.5 h and (b) 1.0 h.
load. Worn material of the coating is accumulated over the wear track; this accumulated worn material caused fluctuation of the penetration depth value during the wear test [2,6]. The Energy Dispersive Spectrum (EDS) analysis of the worn surfaces of Ti–6Al–4V–2B4C coated AISI 1040 steel is shown in Fig. 13. Through EDS analysis, it is confirmed that the wear tracks mainly consists of Ti, Al, V, B, C, Si, Mn, S, P, O, and Fe. The Ti peak in the wear track was identified with high intensity in the EDS analysis. EDS analysis shows the presence of oxide layer in the wear track. The oxide layers were formed due to increase in temperature on the wear track.
3.7.
the sliding wear test was calculated for various sliding velocity and load. Tf ¼
pffiffiffi mV pFn Py 8k
(6)
Flash temperature
This present section deals about the estimation of flash temperature generated during sliding wear of the coating. Flash temperature is the term mentioned as the maximum temperature which is generated during sliding wear test and is explained by Suresh Babu Pitchuka [17]. The flash temperatures of the coatings were estimated using Archard's equation for the material mentioned in Eq. (6) [18]. Flash temperature of
Fig. 13 – EDS of worn surface of Ti–6Al–4V–2B4C coated AISI 1040 steel.
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Table 4 – Flash temperature of various samples. Coating time (h) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
Fn (N)
COF (m)
V (m/s)
Tf (8C)
2 2 2 2 3 3 3 3 2 2 2 2 3 3 3 3
0.43 0.43 0.43 0.43 0.48 0.48 0.48 0.48 0.42 0.42 0.42 0.42 0.45 0.45 0.45 0.45
0.52 0.65 0.79 0.92 0.52 0.65 0.79 0.92 0.52 0.65 0.79 0.92 0.52 0.65 0.79 0.92
27.6 34.6 41.5 48.4 37.8 47.3 56.7 66.2 29.0 33.8 40.5 47.3 35.4 44.3 53.2 62.1
where Tf = flash temperature (8C), m = coefficient of friction, V = velocity (m/s), Fn = normal force (N), Py = yield strength (Pa), and k = thermal conductivity (W/m8C). Table 4 shows the flash temperature of the coated samples with various parameters. The wear tests were performed at room temperature condition (26 8C) and the temperature was raised during the sliding. The thermal conductivity and yield strength of the AISI 1040 steel are 51.9 W/m8C and 415 MPa respectively. Friction at the contact surface will result in heat generation, which subsequently results in temperature increase (flash temperature). Hence it is important to characterize the flash temperatures during sliding. The temperature rise is started from 27.6 8C to a maximum of 48.4 8C for 0.5 h coating time with a normal load of 2 N. The flash temperature of the coating varies from 37.8 8C to 66.2 8C with 0.5 h coating time, which is the highest flash temperature. The better thermal conductivity of the substrate, creating it relatively easier to dissipate the heat through the layer, thus resulting is lower surface flash temperature. The value of flash temperature was calculated as the range between 29 8C and 47.3 8C for 1 h coating with 2 N load. The maximum of flash temperature was obtained as 62.1 8C and the minimum of 35.4 8C for 1 h coating time with 3 N load. The above results clearly show the impact of flash temperature. It is noted that the flash temperature of the coating was increased due to increasing load with sliding velocity and due to increase in surface roughness.
4.
Conclusions
This work has studied the surface morphology, friction, wear behaviour and flash temperature of the Ti–6Al–4V–2B4C coating and the following conclusions are noted. Ti–6Al–4V–2B4C coating were successfully deposited on AISI 1040 steel by magnetron sputtering method of various coating thickness. The prepared Ti–6Al–4V–2B4C coatings were characterized by AFM and XRD. The results show Ti–6Al–4V–2B4C coatings reveal dense uniform structure.
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The coefficient of friction of Ti–6Al–4V–2B4C coated AISI 1040 steel ranges between 0.43 and 0.48 against 0.5 h coatings, 0.42 and 0.45 against 1 h coatings. The coefficients of friction between steel ball and Ti–6Al–4V– 2B4C coated AISI 1040 steel were increased for all combinations with the increase in load. The flash temperature of the coatings has been estimated for various loads and sliding distances. A higher flash temperature of 48.4 8C and 66.2 8C has been estimated for 0.5 h coatings against 2 N and 3 N normal load respectively. The maximum flash temperature of 47.3 8C and 62.1 8C has been estimated for 1 h coatings against 2 N and 3 N normal load is noticed.
references
[1] P.J. Kelly, R.D. Arnell, Magnetron sputtering: a review of recent developments and applications, Vacuum 56 (2000) 159–172. [2] S. Sen, U. Sen, Sliding wear behavior of niobium carbide coated AISI 1040 steel, Wear 264 (2008) 219–225. [3] A.V. Stanishevsky, M.J. Walock, Y. Zou, L. Imhoff, A. Zairi, C. Nouveau, Growth of WC-Cr-N and WC-Al-N coatings in a RF-magnetron sputtering process, Vacuum 90 (2013) 129– 134. [4] N.V. Gavrilov, V.V. Ivanov, A.V. Nikonov, Investigations of Mn–Co–O and Mn–Co–Y–O coatings deposited by the magnetron sputtering on ferritic stainless steels, Surface & Coatings Technology 206 (2011) 1252–1258. [5] H. Pengfei, J. Bailing, Study on tribological property of CrCN coating based on magnetron sputtering plating technique, Vacuum 85 (2011) 994–998. [6] U. Sen, Wear properties of niobium carbide coatings performed by pack method on AISI 1040 steel, Thin Solid Films 483 (2005) 152–157. [7] L. Benea, S.-B. Başa, E. Danaila, N. Caron, O. Raquet, P. Ponthiaux, J.-P. Celis, Fretting and wear behaviors of Ni/nanoWC composite coatings in dry and wet conditions, Materials & Design 65 (2015) 550–558. [8] A. Cavasin, T. Brzezinski, S. Grenier, M. Smagorinski, W and B4C coatings for nuclear fusion reactors, Advanced Materials & Processes 167 (1998) 957–961. [9] R. Harichandran, N. Selvakumar, Effect of nano/micro B4C particles on the mechanical properties of aluminium metal matrix composites fabricated by ultrasonic cavitationassisted solidification process, Archives of Civil and Mechanical Engineering 16 (1) (2016) 147–158. [10] W. Chen, Y. Yamamoto, W.H. Peter, S.B. Gorti, A.S. Sabau, M. B. Clark, S.D. Nunn, J.O. Kiggans, C.A. Blue, J.C. Williams, B. Fuller, K. Akhtar, Cold compaction study of Armstrong process Ti–6Al–4V powders, Powder Technology 214 (2011) 194–199. [11] S.C. Vettivel, N. Selvakumar, N. Leema, Experimental and prediction of sintered Cu–W composite by using artificial neural networks, Materials and Design 45 (2013) 323–335. [12] M. Wang, T. Toihara, M. Sakurai, W. Kurosaka, S. Miyake, Surface morphology and tribological properties of DC sputtered nanoscale multilayered TiAlN/CNx coatings, Tribology International 73 (2014) 36–46. [13] K.W. Xu, G.L. Hou, B.C. Hendrix, J.W. He, Y. Sun, S. Zheng, A. Bloyce, T. Bell, Prediction of nanoindentation hardness profile from a load–displacement curve, Journal of Materials Research 13 (12) (1998) 3519–3526.
292
archives of civil and mechanical engineering 17 (2017) 281–292
[14] C.-H. Tasi, Y.-C. Tseng, S.-R. Jian, Y.-Y. Liao, C.-M. Lin, P.-F. Yang, D.-L. Chen, H.-J. Chen, C.-W. Luo, J.-Y. Juang, Nanomechanical properties of Bi2Te3 thin films by nanoindentation, Journal of Alloys and Compounds 619 (2015) 834–838. [15] M. Yandouzi, A.J. Bottger, R.W.A. Hendrikx, M. Brochu, P. Richer, A. Charest, B. Jodoin, Microstructure and mechanical properties of B4C reinforced Al-based matrix composite coatings deposited by CGDS and PGDS processes, Surface & Coatings Technology 205 (2010) 2234–2246.
[16] Y.-S. Yang, T.-P. Cho, H.-W. Ye, The effect of deposition parameters on the mechanical properties of Cr–C–N coatings, Surface & Coatings Technology 259 (2014) 141–145. [17] S.B. Pitchuka, B. Boesl, C. Zhang, D. Lahiri, Dry sliding wear behavior of cold sprayed aluminum amorphous/ nanocrystalline alloy coatings, Surface & Coatings Technology 238 (2014) 118–125. [18] H.E. Maupin, R.D. Wilson, J.A. Hawk, Wear deformation of ordered Fe-Al intermetallic alloys, Wear 162–164 (1993) 432–440.