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nanocrystalline composite coating synthesized by HVOF spraying
Journal of Alloys and Compounds 825 (2020) 154120
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Journal of Alloys and Compounds journal homepage: http://www.elsevier.com/locate/jalcom
Multi-scale mechanical properties of Fe-based amorphous/ nanocrystalline composite coating synthesized by HVOF spraying Sapan K. Nayak a, Anil Kumar a, Abhishek Pathak b, Atanu Banerjee b, Tapas Laha a, * a b
Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur, 721302, India Research and Development Division, Tata Steel, Jamshedpur, 831007, India
a r t i c l e i n f o
a b s t r a c t
Article history: Received 31 August 2019 Received in revised form 24 January 2020 Accepted 29 January 2020 Available online 31 January 2020
Fe-based (FeeCreBePeC) amorphous/nanocrystalline composite coatings were synthesized by high velocity oxy-fuel (HVOF) thermal spray method with varying powder feed rates and the multi-scale wear behaviour of the coatings’ is reported here. Microstructural characterization of the composite coating envisaged the presence of embedded nanocrystalline phases in the amorphous matrix. The porosity content decreased, whereas the amorphicity of the coating increased gradually with increment in the feed rate. The combined effect of (i) splat morphology and (ii) extent of devitrification on the mechanical and tribological properties of the various coatings was investigated. Increasing the powder feed rate resulted in higher hardness of the coating, which was attributed to better inter-splat bonding and reduction in a-Fe content in the amorphous matrix of the coating due to lower extent of devitrification. Nanotribology test on a single-splat revealed increment in wear resistance at elevated feed rate due to the reduction in volume fraction of softer nanocrystalline a-Fe phases. Besides, dry sliding wear investigated the coatings’ wear behaviour on a global basis and revealed decreasing trends for both wear rate and coefficient of friction with increasing feed rate. Most importantly, the Fe-based composite coatings exhibited low wear volume during nanotribology and lower friction coefficient, low wear rate of dry sliding wear study, compared to an SS316L coating, prepared using industrially optimized parameters. The enhanced wear resistance of the composite coating compared to that of the stainless steel coating makes it an effective method of surface protection for metallic substrates. © 2020 Elsevier B.V. All rights reserved.
Keywords: High velocity oxy-fuel (HVOF) spraying Fe based amorphous/nanocrystalline composite coating Nanohardness Nanotribology Wear
1. Introduction Bulk metallic glasses (BMGs) display an exceptional combination of mechanical and chemical properties, including, superior strength, and outstanding wear and corrosion resistance attributed to absence of long range periodicity of atom [1e3]. But, the intrinsic room temperature brittleness and strain softening of BMGs gravely impedes their industrial application [4,5]. Recently, the development of BMG composites with embedded crystalline secondary phase has proved to be a very effective approach to improve their toughness. This was attributed to the hindrance provided by the crystalline phase to the propagation of shear bands through the amorphous matrix [6,7]. Moreover, the usage of fully amorphous BMGs is limited due to the small critical casting thickness because of low glass forming ability (GFA) [8]. Development of metallic glass
* Corresponding author. E-mail address: [email protected] (T. Laha). https://doi.org/10.1016/j.jallcom.2020.154120 0925-8388/© 2020 Elsevier B.V. All rights reserved.
coatings of thickness in the micrometre range can successfully avert these constraints and widen their application [9,10]. These scenarios led to a drive towards the development of metallic glass composite coatings with nanocrystalline phases embedded in the amorphous matrix. In recent years, various thermally sprayed Febased amorphous/nanocrystalline composite coatings are being inspected as a feasible option of surface modification technique for long-term protection in various sectors, including marine equipment and boilers, etc. [9e12]. Among the various thermal spraying processes, HVOF spraying has been considered extensively because of its flexibility and versatility. The HVOF sprayed coatings exhibited high adhesion strength and low porosity attributed to extremely high velocity encountered by in-flight powder particles [13,14]. Additionally, a relatively high cooling rate (104e105 K/s) of HVOF process favors the evolution of amorphous phase [15]. Zhang et al. [16] synthesized Fe48Cr15Mo14C15B6Y2 fully amorphous coating by HVOF spraying and reported an improvement in wear resistance and attributed it to the higher hardness of the coating. Zhou et al. [17]
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observed an improvement in the wear resistance of the amorphous/nanocrystalline Fe48Cr15Mo14C15B6Y2 coating, which was ascribed to the higher amorphous content and lower porosity of the coating. Recently, Koga et al. [18] studied the tribological and mechanical properties of Fe60Cr8Nb8B24 coating at higher level loading condition and reported high wear resistance of the coating attributed to presence of higher amorphous content with some amount of hard boride phases. Until now, although some investigations on the mechanical and tribological properties of HVOF sprayed Febased amorphous or composite coatings have been carried out, such studies majorly concentrated on the systems having high Cr and Mo and high cost elements like Y, W, etc., making them cost intensive for the industrial usage [19]. In addition, a correlative study between indentation and tribological properties of the Febased composite coatings at multi-scale load is lacking. It was also observed from literature review that investigation on the influence of HVOF spraying parameters on the splat morphology and extent of crystallization and their combined effect on the mechanical and tribological properties of Fe-based composite coating are very limited. Correspondingly, in this work, an Fe-based amorphous/nanocrystalline composite coating with a low Cr and no Mo composition was synthesized by HVOF process with varying powder feed rate. The primary aim of this study was to investigate a correlation between the combined effect of splat morphology and phase evolution, resulting from the different heat input due to varying feed rate of the HVOF process, on the indentation and tribological performance of the synthesized coatings. Another salient aspect of this work is to understand the inter-relationship between indentation and tribological properties of the coatings on a multi-scale basis viz. Low load (nanoindentation and nanoscratch) and high load (microindentation and dry sliding wear). Overall, the present work aspires to systematically investigate the influence of varying powder feed rate of the HVOF process on the indentation and tribological properties of an economical Fe-based composite coating. 2. Experimental procedure The coatings investigated in this work were synthesized from a water atomized Fe-based feedstock powder of composition Fee10Cre4Pe4Be2C, wt.% on grit-blasted mild steel substrate with a HVOF spraying system (HIPOJET-2700, MEC, India). Oxygen, fuel gas, air flow rates and spray distance during the HVOF spraying process were fixed at 270 SLPM, 55e60 SLPM, 460 SLPM and 150 mm, respectively, to deposit coatings of 100 ± 20 mm thickness; while the powder feed rate was varied, ranging from 15 to 50 g/min to achieve different extent of melting. A higher feed rate i.e. greater than 50 g/min was not attempted, considering the saturation in the degree of melting and reduced bond strength due to lowered heat input of the powder particles at higher feed rate [20]. The coatings deposited with varying powder feed rate are represented as Coating-1 (15 g/min), Coating-2 (30 g/min), and Coating-3 (50 g/ min), respectively. An SS316L coating was also prepared using industrially optimized parameters for comparison purpose and denoted as SS coating. The morphology and characteristics of the feedstock powder and coatings were characterized using a scanning electron microscope (SEM, SUPRA 40, Carl Zeiss SMT AG, Germany). The volume fraction of porosity in the deposited coatings was estimated using area analysis method by ImageJ k 1.45 software on at least ten cross-sectional fields of view (500X) of the different coatings after polishing. Phase analysis was examined by X-Ray diffraction (XRD, DY1705, Empyrean, PANalytical, Neatherlands) in the 2q range of 35 e110 using a monochromatic Cr-Ka source. Phase evolution in the coating was further verified by a transmission electron microscopy (FEG-TEM, JEOL, JEM-2100F)
Fig. 1. (a) SEM micrograph and (b) XRD pattern of the water atomized Fe-based amorphous/crystalline feedstock powder used for producing different HVOF sprayed coatings.
using thin slices of the coated sample successively thinned down to 30 mm by mechanical polishing, followed by ion milling with a Gatan precision ion polishing system, model 691. Nanoindentation and nano-scratch tests were conducted with a Triboindenter (TI 950, Hysitron Inc., USA) using a standard three-sided pyramid Berkovich tip (TI-0039, Hysitron Inc., USA) at a peak load of 5000 mN and loading and unloading rate of 500 mN/s. The nanohardness reported here was acquired from the average of 100 indents i.e. 10 10 grid of indents. Constant low load nanoscratch tests were performed with a traverse speed of 0.5 mm s1 for a scratch track length of 10 mm. The scratch trails were examined by in-situ scanning probe microscopy (SPM) to observe their morphology and calculate the wear volume. The tribological properties of the coatings and substrate were evaluated by dry sliding wear test (TE97 Friction and Wear Demonstrator, Phoenix Tribology Ltd., England), with sample as the pin and alumina disc (track diameter 25 mm) as disc. The pin-on-disc test was performed at a load of 10 N, and a constant speed of 0.26 m/s and a sliding distance of 235 m. The worn surface morphology of the composite coating was characterized by the above-mentioned SEM to investigate its wear mechanism. 3. Results and discussion 3.1. Characteristics of the feedstock powder The microstructure and phase composition of the feedstock
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powder are shown in Fig. 1. The nearly-spherical shape of the particles shown in Fig. 1a was attributed to the selection of optimal parameters during the water atomization process [21]. As can be seen Fig. 1a, the size of the particle varied in the range of 5e30 mm. The wider size range and nearly-spherical nature of powders favors good flowability in HVOF spraying process. Fig. 1b showed the XRD analysis of the powders depicting a few sharp crystalline peaks merged on a broad halo peak in the 2q range of 60 e80 , revealed its amorphous/crystalline structure. This composite nature of the powder was attributed to the high GFA (PHSS ¼ 7.31 kJ/mol) of the alloy and relatively high solidification rate (104e106 K/s) during water atomization process helping in the formation of amorphous phase.
3.2. Morphological analysis of the coatings The surface morphology of the coatings deposited at lowest and highest powder feed rate (15 and 50 g/min) are shown in Fig. 2a and b, whereas the size and distribution of porosity was studied from the top polished surface micrographs, shown in Fig. 2d and e. Coating-1 deposited at the lowest powder feed rate, revealed a significantly larger amount of molten particles (Fig. 2a). The fraction of molten particles decreased while that of incompletely melted particles increased with the increment in feed rate from 15 to 50 g/min (Fig. 2a and b). An interestingly decreasing trend in the size and distribution of porosity was envisaged upon elevating the feed rate from 15 to 50 g/min (Fig. 2d and e). Besides, the crosssectional micrographs of the coatings are presented in Fig. 2g and
Fig. 3. XRD patterns of the various HVOF sprayed coatings prepared with different powder feed rates depicting variation in crystallization.
h, which revealed better inter-splat bonding with the increased feed rate. The thickness of Coating-1, Coating-2 and Coating-3 was measured as 93 ± 14, 103 ± 13 and 108 ± 13 mm, respectively. Moreover, the estimated pore volume fraction followed a descending trend with the increase in feed rate and the porosity
Fig. 2. SEM images of (aeb) as-sprayed, (dee) polished top surface and (geh) cross-sectional morphology of the coatings synthesized with the lowest and highest powder feed rate, respectively, (15 and 50 g/min), and (c, f and i) SS316L coating, illustrating the variation in degree of melting and porosity distribution in various coatings.
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Fig. 4. TEM images of (a, b) Coating-1 and Coating-3 with (c, d) corresponding SAD pattern exhibiting the nanocrystalline/amorphous nature of the coating. The extent of devitrification in the coatings decreased from Fig. 4a to b as the feed rate was increased, which was also substantiated from corresponding SAD patterns in Fig. 4c and d.
content (vol. %) were 6.7 ± 1.6, 4.6 ± 1.2, and 2.3 ± 0.5 for Coating-1, Coating-2, and Coating-3, respectively. The reduced porosity content at elevated powder feed rate was attributed to, (i) filling-up of the pores due to higher rate of impingement of particles on the deposited splat and (ii) intensified shot peening effect associated with the HVOF spraying process due to increased particle bombardment [22,23]. The SS coating prepared at 40 g/min exhibited greater amount of well melted particles, thickness of 112 ± 9 mm and porosity content of 2.1 ± 0.4 vol%, which implied the superior quality of the coating owing to its deposition at industrially optimized parameters.
3.3. Phase evolution in the coatings The XRD analysis of the HVOF sprayed Fe-based coatings shown in Fig. 3, revealed a broad halo peak in the 2q range of 60 e80 with few crystalline peaks indicated their amorphous/nanocrystalline composite structure. These crystalline peaks are associated to a-Fe, Fe2B, Fe23B6, Fe3B, FeB and FeP4 phases. Moreover, the peak
corresponding to a-Fe gradually became sharper and intense with decreasing the powder feed rate, revealing higher fraction of a-Fe in Coating-1. Evolution of crystalline phases in the coatings can be attributed to (i) crystallization during solidification of splat, due to higher extent of melting and heat input at the lower powder feed rate [24,25], and (ii) formation of crystalline phases at the intersplat regions of the prepared coatings due to surface oxidation of the molten powder particles during the spraying process [26]. The amorphicity of the coatings was evaluated from the fraction of integrated areas of the crystalline peaks to the area of the amorphous hump [27]. The amorphous phase content was estimated as 71%, 77%, and 81% for Coating-1, Coating-2, and Coating-3, respectively. The above results revealed an increment in amorphicity of the coating upon elevating the feed rate. The lowest amorphicity of Coating-1 was ascribed to precipitation of larger amount of crystalline phase because of higher extent of melting and heat input for the lower feed rate. For the better understanding of the phase evolution in the coatings, TEM study was employed to provide more detailed
Table 1 Mechanical properties obtained from microindentation, nanoindentation and wear studies of the Fe-based amorphous/nanocrystalline composite coatings prepared by HVOF spraying. Samples
Mild steel (substrate)
Coating-1
Coating-2
Coating-3
SS coating
Nanohardness, H (GPa) Vickers micro-hardness (HV0.025) Average scratch depth (nm) Wear volume, Wv (x1021 m3) Coefficient of friction (Dry sliding wear)
3.63 ± 0.24 171 ± 8 e e 0.48 ± 0.06
9.82 ± 2.61 958 ± 121 89.2 ± 1.5 13.5 ± 0.5 0.23 ± 0.04
10.53 ± 2.34 1034 ± 104 56.7 ± 1.1 5.6 ± 0.4 0.16 ± 0.02
11.14 ± 2.41 1091 ± 82 34.2 ± 0.8 2.3 ± 0.2 0.13 ± 0.01
7.12 ± 1.49 691 ± 78 153.1 ± 1.2 40.5 ± 0.3 0.18 ± 0.02
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Fig. 5. (a) Bar graph showing the distribution of indent number density (%) of various HVOF sprayed composite coatings in four different nanohardness range, which are, 5.0e7.5 GPa, 7.5e9.5 GPa, 9.5e12.5 GPa and 12.5e20.0 GPa, corresponding to mixed nano a-Fe and amorphous matrix, amorphous matrix, mixed amorphous and nano intermetallics and nano intermetallics rich regions, respectively, (b) load vs. depth of penetration plots corresponding to different phases i.e. amorphous and intermetallic, present in Coating-3 and crystalline phase of SS coating, and (ced) depth profiles of amorphous and intermetallic regions acquired by in-situ SPM imaging.
information. The TEM micrographs with their corresponding selected area diffraction (SAD) patterns of Coating-1 and Coating-3, sprayed at lowest (15 g/min) and highest (50 g/min) powder feed rate are shown in Fig. 4. It was observed from the TEM images (Fig. 4a and b), that size and volume fraction of crystalline phases in the amorphous matrix of the coating decreased upon elevating the feed rate. Moreover, SAD patterns revealed a reduction in the number of distinct spots in diffused rings from lower (Fig. 4c) to higher (Fig. 4d) feed rate, which validated the higher amorphicity of Coating-3. These findings from the TEM analysis are in well accord with the XRD results discussed earlier in this section.
3.4. Mechanical properties of the coatings Mechanical properties of the HVOF sprayed coatings were investigated by micro-indentation and nanoindentation tests and the results are reported in Table 1. It was observed that, the Febased composite coatings displayed higher microhardness as well as nanohardness than the SS coating. Moreover, an increasing tendency of hardness in coatings was envisaged, in both micro and nano scale with higher powder feed rate. This was ascribed to (i) decreased porosity content at higher feed rate owing to the better inter-splat bonding (Fig. 2), and (ii) reduction in crystalline content in the amorphous matrix of the coating due to lower devitrification (evident from Fig. 3). The decrement in a-Fe content with the elevated feed rate in composite coatings was also validated from the grid indentation technique results, discussed below. Since, it is very difficult to directly measure the volume fraction of different phases present in a coating through microscopy and other methods, in this work, statistical nanoindentation (grid technique of 100 indentations) was carried out obtain the volume fraction of various phases in the coating. Based on the previously reported literature [28e31], the nanohardness range can be divided into four different categories having hardness in the range of 5.0e7.5 GPa, 7.5e9.5 GPa, 9.5e12.5 GPa, and 12.5e20.0 GPa,
corresponding to (1) mixture of nanocrystalline a-Fe and amorphous matrix, (2) amorphous matrix, (3) mixture of amorphous and intermetallic phase, and (4) intermetallic regions, respectively. Graphical representation of the above-mentioned analysis of the coatings is shown in Fig. 5a. It can clearly be deduced from Fig. 5a that the number density of indents in the range of 5.0e7.5 GPa decreased with the increment in powder feed rate. This indicated the gradual reduction in a-Fe content of the coatings upon elevating the feed rate. The indent number density values in the range of 5.0e7.5 GPa for Coating-1 were 30.8%, in comparison to 11.3% in Coating-3. Additionally, the percentage of indents in the 7.5e9.5 GPa range showed an increasing trend, revealed an increment in amorphous phase content with elevating feed rate. However, the indent number density for the hardness of 12.5e20 GPa, belonging to intermetallic rich regions remained almost similar, revealed an insignificant influence of powder feed rate on the intermetallic formation. Although devitrification is higher for lowest powder feed rate, the crystallization effect is related to the precipitation of nanocrystalline a-Fe in the amorphous matrix. The prompt formation of nanocrystalline a-Fe can be ascribed to the primary crystallization of the Fe-based amorphous matrix [32]. The heterogeneous microstructure of the composite coatings i.e. the presence of amorphous and intermetallic phase mixture, can be substantiated from the obtained nanoindentation loaddisplacement curves of the different phases, which can be seen in Fig. 5b. The region rich in intermetallic phase exhibited a higher slope and lower depth of penetration, manifesting its higher nanohardness, compared to amorphous phase which revealed higher depth of penetration. Fig. 5c and d showed the in-situ scanning probe micrographs of depth profiles corresponding to residual impression of indents in amorphous and intermetallic regions, respectively. The decrease in depth of indentation from 73 nm (amorphous phase) to 20 nm (intermetallic phase) substantiates the presence of different phases in the coatings. Additionally, the higher depth of penetration for SS coating (Fig. 5b)
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Fig. 6d, validated its inferior wear resistance. Since the depth profiles presented in Fig. 6e, are nearly symmetrical, volume of the scratch trails i.e. wear volume (Wv) can be obtained from SPM image by using Eq. (1), [34].
1 Wv ¼ cosð70:3 Þ: d2n :l 2
(1)
where, dn is normal displacement and l is length of scratch. It can be observed from the nanoscratch test results reported in Table 1, Coating-3 presented lowest scratch depth (34.2 nm), and lowest wear volume (2.3 1021 m3), establishing its superior wear resistance than that of the other coatings.
3.6. Macro-scale wear behaviour investigated by dry sliding wear The global deformation behaviour of various coatings can be extracted from their macro-wear characterization. The interaction volume during dry sliding wear includes all the heterogeneities in the coatings structure viz. inter-splat boundaries, porosities, etc. Pin-on-disc tribometer was employed to investigate the macroscale wear properties of the coatings. The results of the dry sliding wear test are shown in Fig. 7. Specific wear rate (W in mm3/ Nm) was evaluated by using Eq. (2), given below.
W¼
Fig. 6. (aed) Low load nano-scratch tracks obtained from SPM imaging and (e) 2D cross-sectional scratch profiles of different coatings synthesized by HVOF process.
established the composite coatings as harder ones. 3.5. Nano-scale wear behaviour studied via nano-scratch Owing to the heterogeneous nature of the thermal sprayed coatings, comprising of multi layered splats; the deformation behaviour of a single splat can only be investigated at lower level of loading [33]. Therefore, for understanding the single splat tribological behaviour of the HVOF sprayed composite coating, low load naoscratch test was employed. The wear resistance in this method was evaluated from the depth of scratch groove and wear volume. Fig. 6 presents the in-situ SPM micrographs of the scratch trails and their cross-sectional depth profiles of the different coatings. The width of the scratch trails (Fig. 6aec) revealed a decreasing trend with increase in powder feed rate. Moreover, a reduction in scratch depth was also observed as the feed rate increased from 15 to 50 g/ min, which can be seen in Fig. 6e. This indicated an increment in wear resistance behaviour, which was ascribed to the reduction in volume fraction of softer nanocrystalline a-Fe phases in the coating prepared at higher feed rate, described in the earlier section (Fig. 5a). Besides, the wider and deeper scratch of SS coating in
V S:F
(2)
where, V is wear volume loss in mm3, S is sliding distance in m, and F is applied load in N. Fig. 7a presents the wear rate of the various coatings. It was observed that, all the composite coatings exhibited lower wear rate than the SS coating, which was attributed to their higher hardness. Moreover, wear rate followed a decreasing trend with the increment in powder feed rate. The decreased wear rate was ascribed to the reduced porosity content and higher hardness resulting from well-adhered splats for the coatings at elevated feed rate. Additionally, the wear rate of Coating-3 (9 106 mm3/Nm) was found to be around one-fourth of that of the mild steel substrate (37.9 106 mm3/Nm) and also one-third of that of the SS coating (27.9 106 mm3/Nm), implying enhanced resistance to wear for Coating-3 with respect to that of the substrate as well as SS coating. Fig. 7b illustrated the variation in coefficient of friction (COF) with the sliding distance for substrate and the coatings. The lower value of COF for the coatings was ascribed to their higher hardness. The average COF value of coatings decreased with increasing powder feed rate. The highest value of COF and higher fluctuations in COF curve were observed for Coating-1, which was attributed to the highest porosity content with relatively bigger pores (Fig. 2d) and poorly adhered splat (Fig. 2g). Moreover, penetration depth after the wear test of the coatings followed a descending trend with the increased feed rate in the order of Coating-1 (5.6 ± 0.8 mm) > Coating-2 (3.9 ± 0.5 mm) > Coating-3 (2.5 ± 0.4 mm). The SS coating exhibited a penetration depth of 14.7 ± 0.9 mm, which was higher than those of the composite coatings. This observation is consistent with the specific wear rate and COF results discussed earlier in this section. The worn surface morphology of the Coating-1 was investigated to analyse its mechanism of failure in dry sliding wear environment (Fig. 7c and d). Trace of any adhesive wear was absent on the worn surface of the Fe-based amorphous/nanocrystalline composite coating. However, the presence of cracks was detected in Fig. 7c and d, indicating the dominant wear mechanism of the coating as fatigue wear. During fatigue wear, because of the alternating load effect, the nucleation and propagation of cracks transpire along the
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Fig. 7. (a) Wear rate (b) coefficient of friction (COF) vs. sliding distance plots acquired from dry sliding wear test (pin-on-disc) performed on the coatings and mild steel substrate, (ced) worn surface morphologies of Coating-1, (e) worn surface area of Coating-1 used for EDS mapping, and corresponding EDS mapping of (f) Fe, and (g) O element *Figure a: Ct-1, Ct-2, Ct-3, Ct-SS and MS (sub) corresponds to Coating-1, Coating-2, Coating-3, SS coating and mild steel substrate, respectively.
defective regions of the coating viz. porosity and inter-splat regions, which ultimately leads to its delamination or flaking off from the substrate, illustrated in Fig. 7d [17,35]. Besides, the generated frictional heat during the wear condition can result in oxidative wear [36]. The oxygen mapping of the worn surface of the coating implied the oxidative wear of the coating (Fig. 7g). Therefore, it can be deduced that the mechanism of wear in dry sliding condition of Fe-based amorphous/nanocrystalline coating is fatigue accompanied by oxidative wear. The wear behaviour of the composite coatings was significantly influenced by their characteristics at both nano- (phase composition) and micro-level (porosity, inter-splat boundaries). Wear resistance of composite coatings can be enhanced by the dispersion of nanocrystalline phases in the amorphous matrix, which impede the propagation of shear bands. However, the nature of the
crystalline phases (soft or hard) being flaked off from the coating as debris particle can adversely affect their tribological behaviour. The morphology and size distribution of the debris particles are also very important in this context. It is known that, the hard phases, again depending upon their surface properties, could aggravate the wear problem by causing deep grove formation, or also could act as lubricating particles after their exfoliation from the coatings; whereas, soft phases on the wear track can cause both redeposition phenomenon and adhesive mode of wear [12,37]. As discussed earlier in section 3.3 and 3.4, an increment in amorphicity along with decreased a-Fe phase content was observed upon elevating the feed rate from 15 to 30 g/min, whereas intermetallic phase content remained almost same. Thus, enhanced wear resistance of Coating-3 can be attributed to the reduced abrasion of its worn track due to presence of lower amount of softer a-Fe phase.
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Moreover, tribological characteristics of the coatings are determined by presence of porosity and inter-splat regions on microlevel, as these defects can serve as crack initiation and/or propagation points of fatigue wear or diffusion channel for oxygen atom during oxidative wear, leading to accelerated loss of material. The superior resistance to wear for Coating-3 can also be explained in terms of lowest porosity content and better inter-splat bonding. In addition, the Fe-based composite coatings in this study, exhibited lower friction coefficient, low specific wear rate, compared to the substrate as well as SS coating owing to their higher hardness. Moreover, specific wear rate of Coating-3 (9 106 mm3/Nm) is lower than those of the high Cr and Mo containing HVOF sprayed Fe-based amorphous coatings synthesized by Terajima et al. [38], Wang et al. [39] and Xie et al. [40]. The coatings prepared by Terajima et al., Wang et al. and Xie et al. manifested specific wear rate of ~ 105, ~12.4 106 and ~20 106 mm3/Nm, respectively. Therefore, the application of this composite coating on ductile substrates can be an economical and effective surface protection method under dry sliding wear condition. 4. Conclusions Economical (low Cr and no Mo) highly wear resistant Fe-based amorphous/nanocrystalline composite coatings were deposited on mild steel substrate by high velocity oxy-fuel (HVOF) spraying using water atomized amorphous/crystalline feedstock powder (Fee10Cre4Be4Pe2C, wt.%) with different powder feed rates and the following conclusions can be delineated: 1. Porosity content and the degree of crystallinity (precipitation of nanocrystalline phases) decreased with the increment in feed rate, which were associated to the HVOF shot peening effect and the reduced degree of melting of powder particles, respectively. 2. Higher hardness of the coatings with increased powder feed rate was attributed to better inter-splat bonding and lower extent of devitrification. 3. Increment in the powder feed rate resulted in lower wear volume during nano-scratch test of the coatings, which was ascribed to the reduction in volume fraction of softer nanocrystalline a-Fe phases at higher feed rate. 4. Dry sliding wear study revealed decreasing trends for both wear rate and coefficient of friction with increasing feed rate due to better inter-splat bonding and lower porosity content of the coatings. 5. Most importantly, the Fe-based composite coatings exhibited low wear volume during nano-scratch test and lower friction coefficient, low specific wear rate of dry sliding wear study, compared to the substrate as well as the SS coating. In addition, wear rate of the coating deposited at highest feed rate of 50 g/ min i.e. Coating-3 was found to be around one-fourth of that of the substrate and also one-third of that of the SS coating, implying enhanced resistance to wear for Coating-3 compared to other coatings.
Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. CRediT authorship contribution statement Sapan
K.
Nayak:
Conceptualization,
Methodology,
Investigation, Formal analysis, Data curation, Visualization, Writing - original draft. Anil Kumar: Methodology, Investigation, Formal analysis. Abhishek Pathak: Methodology. Atanu Banerjee: Methodology, Resources, Project administration. Tapas Laha: Conceptualization, Supervision, Validation, Writing - review & editing, Resources, Project administration. Acknowledgements The author, T. Laha thankfully acknowledges the financial support obtained from Research and Development Division of Tata Steel, India. References [1] C. Suryanarayana, A. Inoue, Iron-based bulk metallic glasses, Int. Mater. Rev. 58 (2012) 131e166. [2] D.H. Kwon, E.S. Park, M.Y. Huh, H.J. Kim, J.C. Bae, Wear behavior of Fe-based bulk metallic glass composites, J. Alloys Compd. 509 (2011) S105eS108. [3] D.D. Liang, X.S. Wei, C.T. Chang, J.W. Li, X.M. Wang, J. Shen, Effect of W addition on the glass forming ability and mechanical properties of Fe-based metallic glass, J. Alloys Compd. 731 (2018) 1146e1150. [4] M.F. Ashby, A.L. Greer, Metallic glasses as structural materials, Scripta Mater. 54 (2006) 321e326. [5] M. Chen, Mechanical behavior of metallic glasses: microscopic understanding of strength and ductility, Annu. Rev. Mater. Res. 38 (2008) 445e469. [6] S.F. Guo, L. Liu, N. Li, Y. Li, Fe-based bulk metallic glass matrix composite with large plasticity, Scripta Mater. 62 (2010) 329e332. [7] W. Yang, H. Liu, Y. Zhao, A. Inoue, K. Jiang, J. Huo, H. Ling, Q. Li, B. Shen, Mechanical properties and structural features of novel fe-based bulk metallic glasses with unprecedented plasticity, Sci. Rep. 4 (2014) 1e6. [8] X.J. Gu, S.J. Poon, G.J. Shiflet, Mechanical properties of iron-based bulk metallic glasses, J. Mater. Res. 22 (2007) 344e351. [9] W. Guo, Y. Wu, J. Zhang, S. Hong, G. Li, G. Ying, J. Guo, Y. Qin, Fabrication and characterization of thermal-sprayed Fe-based amorphous/nanocrystalline composite coatings: an overview, J. Therm. Spray Technol. 23 (2014) 1157e1180. [10] Y. Wang, M.Y. Li, L.L. Sun, X.Y. Zhang, J. Shen, Environmentally assisted fracture behavior of Fe-based amorphous coatings in chloride-containing solutions, J. Alloys Compd. 738 (2018) 37e48. [11] B.Y. Fu, D.Y. He, L.D. Zhao, Effect of heat treatment on the microstructure and mechanical properties of Fe-based amorphous coatings, J. Alloys Compd. 480 (2009) 422e427. [12] L. Liu, J.K. Xiao, X. Wei, Y. Ren, G. Zhang, C. Zhang, Effects of temperature and atmosphere on microstructure and tribological properties of plasma sprayed FeCrBSi coatings, J. Alloys Compd. 753 (2018) 586e594. [13] M.P. Planche, H. Liao, B. Normand, C. Coddet, Relationships between NiCrBSi particle characteristics and corresponding coating properties using different thermal spraying processes, Surf. Coating. Technol. 200 (2005) 2465e2473. [14] S. Sampath, X.Y. Jiang, J. Matejicek, L. Prchlik, A. Kulkarni, A. Vaidya, Role of thermal spray processing method on the microstructure, residual stress and properties of coatings: an integrated study of Ni-5 wt. % Al bond coats, Mater. Sci. Eng. A. 364 (2004) 216e231. [15] H.J. Kim, K.M. Lim, B.G. Seong, C.G. Park, Amorphous phase formation of Zrbased alloy coating by HVOF spraying process, J. Mater. Sci. 36 (2001) 49e54. [16] C. Zhang, L. Liu, K.C. Chan, Q. Chen, C.Y. Tang, Wear behavior of HVOF-sprayed Fe-based amorphous coatings, Intermetallics 29 (2012) 80e85. [17] Z. Zhou, L. Wang, D.Y. He, F.C. Wang, Y.B. Liu, Microstructure and wear resistance of Fe-based amorphous metallic coatings prepared by HVOF thermal spraying, J. Therm. Spray Technol. 19 (2010) 1287e1293. [18] G.Y. Koga, R. Schulz, S. Savoie, A.R.C. Nascimento, Y. Drolet, C. Bolfarini, C.S. Kiminami, W.J. Botta, Microstructure and wear behavior of Fe-based amorphous HVOF coatings produced from commercial precursors, Surf. Coating. Technol. 309 (2017) 938e944. [19] J. Li, L. Yang, H. Ma, K. Jiang, C. Chang, J.Q. Wang, Z. Song, X. Wang, R.W. Li, Improved corrosion resistance of novel Fe-based amorphous alloys, Mater. Des. 95 (2016) 225e230. [20] M. Taheri, Z. Valefi, K. Zangeneh-Madar, Influence of HVOF process parameters on microstructure and bond strength of NiCrAlY coatings, Surf. Eng. 28 (2012) 266e272. [21] B. Hausnerova, B.N. Mukund, D. Sanetrnik, Rheological properties of gas and water atomized 17-4PH stainless steel MIM feedstocks: effect of powder shape and size, Powder Technol. 312 (2017) 152e158. [22] M. Li, P.D. Christofides, Modeling and control of high-velocity oxygen-fuel (HVOF) thermal spray: a tutorial review, J. Therm. Spray Technol. 18 (2009) 753e768. [23] D. Zois, A. Lekatou, M. Vardavoulias, T. Vaimakis, A.E. Karantzalis, Partially amorphous stainless steel coatings: microstructure, annealing behavior and statistical optimization of spray parameters, Surf. Coating. Technol. 206 (2011) 1469e1483.
S.K. Nayak et al. / Journal of Alloys and Compounds 825 (2020) 154120 [24] P. Bansal, P.H. Shipway, S.B. Leen, Residual stresses in high-velocity oxy-fuel thermally sprayed coatings - modelling the effect of particle velocity and temperature during the spraying process, Acta Mater. 55 (2007) 5089e5101. [25] L. Qiao, Y. Wu, S. Hong, J. Cheng, Z. Wei, Influence of the high-velocity oxygenfuel spray parameters on the porosity and corrosion resistance of iron-based amorphous coatings, Surf. Coating. Technol. 366 (2019) 296e302. [26] Y. Wang, S.L. Jiang, Y.G. Zheng, W. Ke, W.H. Sun, X.C. Chang, W.L. Hou, J.Q. Wang, Effect of processing parameters on the microstructures and corrosion behaviour of high-velocity oxy-fuel (HVOF) sprayed Fe-based amorphous metallic coatings, Mater. Corros. 64 (2013) 801e810. [27] J. Wu, S.D. Zhang, W.H. Sun, Y. Gao, J.Q. Wang, Enhanced corrosion resistance in Fe-based amorphous coatings through eliminating Cr-depleted zones, Corrosion Sci. 136 (2018) 161e173. [28] R.S. Maurya, A. Sahu, T. Laha, Quantitative phase analysis in Al86Ni8Y6 bulk glassy alloy synthesized by consolidating mechanically alloyed amorphous powder via spark plasma sintering, Mater. Des. 93 (2016) 96e103. [29] Y.Y. Sun, M. Song, X.Z. Liao, G. Sha, Y.H. He, Effects of isothermal annealing on the microstructures and mechanical properties of a FeCuSiBAl amorphous alloy, Mater. Sci. Eng. A. 543 (2012) 145e151. [30] A. Kumar, R. Kumar, P. Bijalwan, M. Dutta, A. Banerjee, T. Laha, Fe-based amorphous/nanocrystalline composite coating by plasma spraying: effect of heat input on morphology, phase evolution and mechanical properties, J. Alloys Compd. 771 (2019) 827e837. [31] A. Agarwal, N.B. Dahotre, Mechanical properties of laser-deposited composite boride coating using nanoindentation, Metall. Mater. Trans. A Phys. Metall. Mater. Sci. 31 (2000) 401e408. [32] D.M. Mini c, A. Mari ci c, B. Adnadevi c, Crystallization of a-Fe phase in amorphous Fe81B13Si4C2 alloy, J. Alloys Compd. 473 (2009) 363e367.
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[33] A. Loganathan, A. Sahu, C. Rudolf, C. Zhang, S. Rengifo, T. Laha, B. Boesl, A. Agarwal, Multi-scale tribological and nanomechanical behavior of cold sprayed Ti2AlC MAX phase coating, Surf. Coating. Technol. 334 (2018) 384e393. [34] K. Balani, S.P. Harimkar, A. Keshri, Y. Chen, N.B. Dahotre, A. Agarwal, Multiscale wear of plasma-sprayed carbon-nanotube-reinforced aluminum oxide nanocomposite coating, Acta Mater. 56 (2008) 5984e5994. [35] J.B. Cheng, X.B. Liang, Z.H. Wang, B.S. Xu, Dry sliding friction and wear properties of metallic glass coating and martensite stainless coating, Tribol. Int. 60 (2013) 140e146. [36] L. Xie, X. Xiong, Y. Zeng, Y. Wang, The wear properties and mechanism of detonation sprayed iron-based amorphous coating, Surf. Coating. Technol. 366 (2019) 146e155. [37] C. Si, B. Duan, Q. Zhang, J. Cai, W. Wu, Microstructure, corrosion-resistance, and wear-resistance properties of subsonic flame sprayed amorphous Fe e Mo e Cr e Co coating with extremely high amorphous rate, J. Mater. Res. Technol. (2020) 1e12. [38] T. Terajima, F. Takeuchi, K. Nakata, S. Adachi, K. Nakashima, T. Igarashi, Composite coating containing WC/12Co cermet and Fe-based metallic glass deposited by high-velocity oxygen fuel spraying, J. Alloys Compd. 504S (2010) S288eS291. [39] W. Wang, C. Zhang, P. Xu, M. Yasir, L. Liu, Enhancement of oxidation and wear resistance of Fe-based amorphous coatings by surface modification of feedstock powders, Mater. Des. 73 (2015) 35e41. [40] L. Xie, Y.M. Wang, X. Xiong, Z.K. Chen, Comparison of microstructure and tribological properties of plasma, high velocity oxy-fuel and detonation sprayed coatings from an iron-based powder, Mater. Trans. 59 (2018) 1591e1595.
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Journal of Alloys and Compounds journal homepage: http://www.elsevier.com/locate/jalcom
Multi-scale mechanical properties of Fe-based amorphous/ nanocrystalline composite coating synthesized by HVOF spraying Sapan K. Nayak a, Anil Kumar a, Abhishek Pathak b, Atanu Banerjee b, Tapas Laha a, * a b
Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur, 721302, India Research and Development Division, Tata Steel, Jamshedpur, 831007, India
a r t i c l e i n f o
a b s t r a c t
Article history: Received 31 August 2019 Received in revised form 24 January 2020 Accepted 29 January 2020 Available online 31 January 2020
Fe-based (FeeCreBePeC) amorphous/nanocrystalline composite coatings were synthesized by high velocity oxy-fuel (HVOF) thermal spray method with varying powder feed rates and the multi-scale wear behaviour of the coatings’ is reported here. Microstructural characterization of the composite coating envisaged the presence of embedded nanocrystalline phases in the amorphous matrix. The porosity content decreased, whereas the amorphicity of the coating increased gradually with increment in the feed rate. The combined effect of (i) splat morphology and (ii) extent of devitrification on the mechanical and tribological properties of the various coatings was investigated. Increasing the powder feed rate resulted in higher hardness of the coating, which was attributed to better inter-splat bonding and reduction in a-Fe content in the amorphous matrix of the coating due to lower extent of devitrification. Nanotribology test on a single-splat revealed increment in wear resistance at elevated feed rate due to the reduction in volume fraction of softer nanocrystalline a-Fe phases. Besides, dry sliding wear investigated the coatings’ wear behaviour on a global basis and revealed decreasing trends for both wear rate and coefficient of friction with increasing feed rate. Most importantly, the Fe-based composite coatings exhibited low wear volume during nanotribology and lower friction coefficient, low wear rate of dry sliding wear study, compared to an SS316L coating, prepared using industrially optimized parameters. The enhanced wear resistance of the composite coating compared to that of the stainless steel coating makes it an effective method of surface protection for metallic substrates. © 2020 Elsevier B.V. All rights reserved.
Keywords: High velocity oxy-fuel (HVOF) spraying Fe based amorphous/nanocrystalline composite coating Nanohardness Nanotribology Wear
1. Introduction Bulk metallic glasses (BMGs) display an exceptional combination of mechanical and chemical properties, including, superior strength, and outstanding wear and corrosion resistance attributed to absence of long range periodicity of atom [1e3]. But, the intrinsic room temperature brittleness and strain softening of BMGs gravely impedes their industrial application [4,5]. Recently, the development of BMG composites with embedded crystalline secondary phase has proved to be a very effective approach to improve their toughness. This was attributed to the hindrance provided by the crystalline phase to the propagation of shear bands through the amorphous matrix [6,7]. Moreover, the usage of fully amorphous BMGs is limited due to the small critical casting thickness because of low glass forming ability (GFA) [8]. Development of metallic glass
* Corresponding author. E-mail address: [email protected] (T. Laha). https://doi.org/10.1016/j.jallcom.2020.154120 0925-8388/© 2020 Elsevier B.V. All rights reserved.
coatings of thickness in the micrometre range can successfully avert these constraints and widen their application [9,10]. These scenarios led to a drive towards the development of metallic glass composite coatings with nanocrystalline phases embedded in the amorphous matrix. In recent years, various thermally sprayed Febased amorphous/nanocrystalline composite coatings are being inspected as a feasible option of surface modification technique for long-term protection in various sectors, including marine equipment and boilers, etc. [9e12]. Among the various thermal spraying processes, HVOF spraying has been considered extensively because of its flexibility and versatility. The HVOF sprayed coatings exhibited high adhesion strength and low porosity attributed to extremely high velocity encountered by in-flight powder particles [13,14]. Additionally, a relatively high cooling rate (104e105 K/s) of HVOF process favors the evolution of amorphous phase [15]. Zhang et al. [16] synthesized Fe48Cr15Mo14C15B6Y2 fully amorphous coating by HVOF spraying and reported an improvement in wear resistance and attributed it to the higher hardness of the coating. Zhou et al. [17]
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observed an improvement in the wear resistance of the amorphous/nanocrystalline Fe48Cr15Mo14C15B6Y2 coating, which was ascribed to the higher amorphous content and lower porosity of the coating. Recently, Koga et al. [18] studied the tribological and mechanical properties of Fe60Cr8Nb8B24 coating at higher level loading condition and reported high wear resistance of the coating attributed to presence of higher amorphous content with some amount of hard boride phases. Until now, although some investigations on the mechanical and tribological properties of HVOF sprayed Febased amorphous or composite coatings have been carried out, such studies majorly concentrated on the systems having high Cr and Mo and high cost elements like Y, W, etc., making them cost intensive for the industrial usage [19]. In addition, a correlative study between indentation and tribological properties of the Febased composite coatings at multi-scale load is lacking. It was also observed from literature review that investigation on the influence of HVOF spraying parameters on the splat morphology and extent of crystallization and their combined effect on the mechanical and tribological properties of Fe-based composite coating are very limited. Correspondingly, in this work, an Fe-based amorphous/nanocrystalline composite coating with a low Cr and no Mo composition was synthesized by HVOF process with varying powder feed rate. The primary aim of this study was to investigate a correlation between the combined effect of splat morphology and phase evolution, resulting from the different heat input due to varying feed rate of the HVOF process, on the indentation and tribological performance of the synthesized coatings. Another salient aspect of this work is to understand the inter-relationship between indentation and tribological properties of the coatings on a multi-scale basis viz. Low load (nanoindentation and nanoscratch) and high load (microindentation and dry sliding wear). Overall, the present work aspires to systematically investigate the influence of varying powder feed rate of the HVOF process on the indentation and tribological properties of an economical Fe-based composite coating. 2. Experimental procedure The coatings investigated in this work were synthesized from a water atomized Fe-based feedstock powder of composition Fee10Cre4Pe4Be2C, wt.% on grit-blasted mild steel substrate with a HVOF spraying system (HIPOJET-2700, MEC, India). Oxygen, fuel gas, air flow rates and spray distance during the HVOF spraying process were fixed at 270 SLPM, 55e60 SLPM, 460 SLPM and 150 mm, respectively, to deposit coatings of 100 ± 20 mm thickness; while the powder feed rate was varied, ranging from 15 to 50 g/min to achieve different extent of melting. A higher feed rate i.e. greater than 50 g/min was not attempted, considering the saturation in the degree of melting and reduced bond strength due to lowered heat input of the powder particles at higher feed rate [20]. The coatings deposited with varying powder feed rate are represented as Coating-1 (15 g/min), Coating-2 (30 g/min), and Coating-3 (50 g/ min), respectively. An SS316L coating was also prepared using industrially optimized parameters for comparison purpose and denoted as SS coating. The morphology and characteristics of the feedstock powder and coatings were characterized using a scanning electron microscope (SEM, SUPRA 40, Carl Zeiss SMT AG, Germany). The volume fraction of porosity in the deposited coatings was estimated using area analysis method by ImageJ k 1.45 software on at least ten cross-sectional fields of view (500X) of the different coatings after polishing. Phase analysis was examined by X-Ray diffraction (XRD, DY1705, Empyrean, PANalytical, Neatherlands) in the 2q range of 35 e110 using a monochromatic Cr-Ka source. Phase evolution in the coating was further verified by a transmission electron microscopy (FEG-TEM, JEOL, JEM-2100F)
Fig. 1. (a) SEM micrograph and (b) XRD pattern of the water atomized Fe-based amorphous/crystalline feedstock powder used for producing different HVOF sprayed coatings.
using thin slices of the coated sample successively thinned down to 30 mm by mechanical polishing, followed by ion milling with a Gatan precision ion polishing system, model 691. Nanoindentation and nano-scratch tests were conducted with a Triboindenter (TI 950, Hysitron Inc., USA) using a standard three-sided pyramid Berkovich tip (TI-0039, Hysitron Inc., USA) at a peak load of 5000 mN and loading and unloading rate of 500 mN/s. The nanohardness reported here was acquired from the average of 100 indents i.e. 10 10 grid of indents. Constant low load nanoscratch tests were performed with a traverse speed of 0.5 mm s1 for a scratch track length of 10 mm. The scratch trails were examined by in-situ scanning probe microscopy (SPM) to observe their morphology and calculate the wear volume. The tribological properties of the coatings and substrate were evaluated by dry sliding wear test (TE97 Friction and Wear Demonstrator, Phoenix Tribology Ltd., England), with sample as the pin and alumina disc (track diameter 25 mm) as disc. The pin-on-disc test was performed at a load of 10 N, and a constant speed of 0.26 m/s and a sliding distance of 235 m. The worn surface morphology of the composite coating was characterized by the above-mentioned SEM to investigate its wear mechanism. 3. Results and discussion 3.1. Characteristics of the feedstock powder The microstructure and phase composition of the feedstock
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powder are shown in Fig. 1. The nearly-spherical shape of the particles shown in Fig. 1a was attributed to the selection of optimal parameters during the water atomization process [21]. As can be seen Fig. 1a, the size of the particle varied in the range of 5e30 mm. The wider size range and nearly-spherical nature of powders favors good flowability in HVOF spraying process. Fig. 1b showed the XRD analysis of the powders depicting a few sharp crystalline peaks merged on a broad halo peak in the 2q range of 60 e80 , revealed its amorphous/crystalline structure. This composite nature of the powder was attributed to the high GFA (PHSS ¼ 7.31 kJ/mol) of the alloy and relatively high solidification rate (104e106 K/s) during water atomization process helping in the formation of amorphous phase.
3.2. Morphological analysis of the coatings The surface morphology of the coatings deposited at lowest and highest powder feed rate (15 and 50 g/min) are shown in Fig. 2a and b, whereas the size and distribution of porosity was studied from the top polished surface micrographs, shown in Fig. 2d and e. Coating-1 deposited at the lowest powder feed rate, revealed a significantly larger amount of molten particles (Fig. 2a). The fraction of molten particles decreased while that of incompletely melted particles increased with the increment in feed rate from 15 to 50 g/min (Fig. 2a and b). An interestingly decreasing trend in the size and distribution of porosity was envisaged upon elevating the feed rate from 15 to 50 g/min (Fig. 2d and e). Besides, the crosssectional micrographs of the coatings are presented in Fig. 2g and
Fig. 3. XRD patterns of the various HVOF sprayed coatings prepared with different powder feed rates depicting variation in crystallization.
h, which revealed better inter-splat bonding with the increased feed rate. The thickness of Coating-1, Coating-2 and Coating-3 was measured as 93 ± 14, 103 ± 13 and 108 ± 13 mm, respectively. Moreover, the estimated pore volume fraction followed a descending trend with the increase in feed rate and the porosity
Fig. 2. SEM images of (aeb) as-sprayed, (dee) polished top surface and (geh) cross-sectional morphology of the coatings synthesized with the lowest and highest powder feed rate, respectively, (15 and 50 g/min), and (c, f and i) SS316L coating, illustrating the variation in degree of melting and porosity distribution in various coatings.
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Fig. 4. TEM images of (a, b) Coating-1 and Coating-3 with (c, d) corresponding SAD pattern exhibiting the nanocrystalline/amorphous nature of the coating. The extent of devitrification in the coatings decreased from Fig. 4a to b as the feed rate was increased, which was also substantiated from corresponding SAD patterns in Fig. 4c and d.
content (vol. %) were 6.7 ± 1.6, 4.6 ± 1.2, and 2.3 ± 0.5 for Coating-1, Coating-2, and Coating-3, respectively. The reduced porosity content at elevated powder feed rate was attributed to, (i) filling-up of the pores due to higher rate of impingement of particles on the deposited splat and (ii) intensified shot peening effect associated with the HVOF spraying process due to increased particle bombardment [22,23]. The SS coating prepared at 40 g/min exhibited greater amount of well melted particles, thickness of 112 ± 9 mm and porosity content of 2.1 ± 0.4 vol%, which implied the superior quality of the coating owing to its deposition at industrially optimized parameters.
3.3. Phase evolution in the coatings The XRD analysis of the HVOF sprayed Fe-based coatings shown in Fig. 3, revealed a broad halo peak in the 2q range of 60 e80 with few crystalline peaks indicated their amorphous/nanocrystalline composite structure. These crystalline peaks are associated to a-Fe, Fe2B, Fe23B6, Fe3B, FeB and FeP4 phases. Moreover, the peak
corresponding to a-Fe gradually became sharper and intense with decreasing the powder feed rate, revealing higher fraction of a-Fe in Coating-1. Evolution of crystalline phases in the coatings can be attributed to (i) crystallization during solidification of splat, due to higher extent of melting and heat input at the lower powder feed rate [24,25], and (ii) formation of crystalline phases at the intersplat regions of the prepared coatings due to surface oxidation of the molten powder particles during the spraying process [26]. The amorphicity of the coatings was evaluated from the fraction of integrated areas of the crystalline peaks to the area of the amorphous hump [27]. The amorphous phase content was estimated as 71%, 77%, and 81% for Coating-1, Coating-2, and Coating-3, respectively. The above results revealed an increment in amorphicity of the coating upon elevating the feed rate. The lowest amorphicity of Coating-1 was ascribed to precipitation of larger amount of crystalline phase because of higher extent of melting and heat input for the lower feed rate. For the better understanding of the phase evolution in the coatings, TEM study was employed to provide more detailed
Table 1 Mechanical properties obtained from microindentation, nanoindentation and wear studies of the Fe-based amorphous/nanocrystalline composite coatings prepared by HVOF spraying. Samples
Mild steel (substrate)
Coating-1
Coating-2
Coating-3
SS coating
Nanohardness, H (GPa) Vickers micro-hardness (HV0.025) Average scratch depth (nm) Wear volume, Wv (x1021 m3) Coefficient of friction (Dry sliding wear)
3.63 ± 0.24 171 ± 8 e e 0.48 ± 0.06
9.82 ± 2.61 958 ± 121 89.2 ± 1.5 13.5 ± 0.5 0.23 ± 0.04
10.53 ± 2.34 1034 ± 104 56.7 ± 1.1 5.6 ± 0.4 0.16 ± 0.02
11.14 ± 2.41 1091 ± 82 34.2 ± 0.8 2.3 ± 0.2 0.13 ± 0.01
7.12 ± 1.49 691 ± 78 153.1 ± 1.2 40.5 ± 0.3 0.18 ± 0.02
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Fig. 5. (a) Bar graph showing the distribution of indent number density (%) of various HVOF sprayed composite coatings in four different nanohardness range, which are, 5.0e7.5 GPa, 7.5e9.5 GPa, 9.5e12.5 GPa and 12.5e20.0 GPa, corresponding to mixed nano a-Fe and amorphous matrix, amorphous matrix, mixed amorphous and nano intermetallics and nano intermetallics rich regions, respectively, (b) load vs. depth of penetration plots corresponding to different phases i.e. amorphous and intermetallic, present in Coating-3 and crystalline phase of SS coating, and (ced) depth profiles of amorphous and intermetallic regions acquired by in-situ SPM imaging.
information. The TEM micrographs with their corresponding selected area diffraction (SAD) patterns of Coating-1 and Coating-3, sprayed at lowest (15 g/min) and highest (50 g/min) powder feed rate are shown in Fig. 4. It was observed from the TEM images (Fig. 4a and b), that size and volume fraction of crystalline phases in the amorphous matrix of the coating decreased upon elevating the feed rate. Moreover, SAD patterns revealed a reduction in the number of distinct spots in diffused rings from lower (Fig. 4c) to higher (Fig. 4d) feed rate, which validated the higher amorphicity of Coating-3. These findings from the TEM analysis are in well accord with the XRD results discussed earlier in this section.
3.4. Mechanical properties of the coatings Mechanical properties of the HVOF sprayed coatings were investigated by micro-indentation and nanoindentation tests and the results are reported in Table 1. It was observed that, the Febased composite coatings displayed higher microhardness as well as nanohardness than the SS coating. Moreover, an increasing tendency of hardness in coatings was envisaged, in both micro and nano scale with higher powder feed rate. This was ascribed to (i) decreased porosity content at higher feed rate owing to the better inter-splat bonding (Fig. 2), and (ii) reduction in crystalline content in the amorphous matrix of the coating due to lower devitrification (evident from Fig. 3). The decrement in a-Fe content with the elevated feed rate in composite coatings was also validated from the grid indentation technique results, discussed below. Since, it is very difficult to directly measure the volume fraction of different phases present in a coating through microscopy and other methods, in this work, statistical nanoindentation (grid technique of 100 indentations) was carried out obtain the volume fraction of various phases in the coating. Based on the previously reported literature [28e31], the nanohardness range can be divided into four different categories having hardness in the range of 5.0e7.5 GPa, 7.5e9.5 GPa, 9.5e12.5 GPa, and 12.5e20.0 GPa,
corresponding to (1) mixture of nanocrystalline a-Fe and amorphous matrix, (2) amorphous matrix, (3) mixture of amorphous and intermetallic phase, and (4) intermetallic regions, respectively. Graphical representation of the above-mentioned analysis of the coatings is shown in Fig. 5a. It can clearly be deduced from Fig. 5a that the number density of indents in the range of 5.0e7.5 GPa decreased with the increment in powder feed rate. This indicated the gradual reduction in a-Fe content of the coatings upon elevating the feed rate. The indent number density values in the range of 5.0e7.5 GPa for Coating-1 were 30.8%, in comparison to 11.3% in Coating-3. Additionally, the percentage of indents in the 7.5e9.5 GPa range showed an increasing trend, revealed an increment in amorphous phase content with elevating feed rate. However, the indent number density for the hardness of 12.5e20 GPa, belonging to intermetallic rich regions remained almost similar, revealed an insignificant influence of powder feed rate on the intermetallic formation. Although devitrification is higher for lowest powder feed rate, the crystallization effect is related to the precipitation of nanocrystalline a-Fe in the amorphous matrix. The prompt formation of nanocrystalline a-Fe can be ascribed to the primary crystallization of the Fe-based amorphous matrix [32]. The heterogeneous microstructure of the composite coatings i.e. the presence of amorphous and intermetallic phase mixture, can be substantiated from the obtained nanoindentation loaddisplacement curves of the different phases, which can be seen in Fig. 5b. The region rich in intermetallic phase exhibited a higher slope and lower depth of penetration, manifesting its higher nanohardness, compared to amorphous phase which revealed higher depth of penetration. Fig. 5c and d showed the in-situ scanning probe micrographs of depth profiles corresponding to residual impression of indents in amorphous and intermetallic regions, respectively. The decrease in depth of indentation from 73 nm (amorphous phase) to 20 nm (intermetallic phase) substantiates the presence of different phases in the coatings. Additionally, the higher depth of penetration for SS coating (Fig. 5b)
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Fig. 6d, validated its inferior wear resistance. Since the depth profiles presented in Fig. 6e, are nearly symmetrical, volume of the scratch trails i.e. wear volume (Wv) can be obtained from SPM image by using Eq. (1), [34].
1 Wv ¼ cosð70:3 Þ: d2n :l 2
(1)
where, dn is normal displacement and l is length of scratch. It can be observed from the nanoscratch test results reported in Table 1, Coating-3 presented lowest scratch depth (34.2 nm), and lowest wear volume (2.3 1021 m3), establishing its superior wear resistance than that of the other coatings.
3.6. Macro-scale wear behaviour investigated by dry sliding wear The global deformation behaviour of various coatings can be extracted from their macro-wear characterization. The interaction volume during dry sliding wear includes all the heterogeneities in the coatings structure viz. inter-splat boundaries, porosities, etc. Pin-on-disc tribometer was employed to investigate the macroscale wear properties of the coatings. The results of the dry sliding wear test are shown in Fig. 7. Specific wear rate (W in mm3/ Nm) was evaluated by using Eq. (2), given below.
W¼
Fig. 6. (aed) Low load nano-scratch tracks obtained from SPM imaging and (e) 2D cross-sectional scratch profiles of different coatings synthesized by HVOF process.
established the composite coatings as harder ones. 3.5. Nano-scale wear behaviour studied via nano-scratch Owing to the heterogeneous nature of the thermal sprayed coatings, comprising of multi layered splats; the deformation behaviour of a single splat can only be investigated at lower level of loading [33]. Therefore, for understanding the single splat tribological behaviour of the HVOF sprayed composite coating, low load naoscratch test was employed. The wear resistance in this method was evaluated from the depth of scratch groove and wear volume. Fig. 6 presents the in-situ SPM micrographs of the scratch trails and their cross-sectional depth profiles of the different coatings. The width of the scratch trails (Fig. 6aec) revealed a decreasing trend with increase in powder feed rate. Moreover, a reduction in scratch depth was also observed as the feed rate increased from 15 to 50 g/ min, which can be seen in Fig. 6e. This indicated an increment in wear resistance behaviour, which was ascribed to the reduction in volume fraction of softer nanocrystalline a-Fe phases in the coating prepared at higher feed rate, described in the earlier section (Fig. 5a). Besides, the wider and deeper scratch of SS coating in
V S:F
(2)
where, V is wear volume loss in mm3, S is sliding distance in m, and F is applied load in N. Fig. 7a presents the wear rate of the various coatings. It was observed that, all the composite coatings exhibited lower wear rate than the SS coating, which was attributed to their higher hardness. Moreover, wear rate followed a decreasing trend with the increment in powder feed rate. The decreased wear rate was ascribed to the reduced porosity content and higher hardness resulting from well-adhered splats for the coatings at elevated feed rate. Additionally, the wear rate of Coating-3 (9 106 mm3/Nm) was found to be around one-fourth of that of the mild steel substrate (37.9 106 mm3/Nm) and also one-third of that of the SS coating (27.9 106 mm3/Nm), implying enhanced resistance to wear for Coating-3 with respect to that of the substrate as well as SS coating. Fig. 7b illustrated the variation in coefficient of friction (COF) with the sliding distance for substrate and the coatings. The lower value of COF for the coatings was ascribed to their higher hardness. The average COF value of coatings decreased with increasing powder feed rate. The highest value of COF and higher fluctuations in COF curve were observed for Coating-1, which was attributed to the highest porosity content with relatively bigger pores (Fig. 2d) and poorly adhered splat (Fig. 2g). Moreover, penetration depth after the wear test of the coatings followed a descending trend with the increased feed rate in the order of Coating-1 (5.6 ± 0.8 mm) > Coating-2 (3.9 ± 0.5 mm) > Coating-3 (2.5 ± 0.4 mm). The SS coating exhibited a penetration depth of 14.7 ± 0.9 mm, which was higher than those of the composite coatings. This observation is consistent with the specific wear rate and COF results discussed earlier in this section. The worn surface morphology of the Coating-1 was investigated to analyse its mechanism of failure in dry sliding wear environment (Fig. 7c and d). Trace of any adhesive wear was absent on the worn surface of the Fe-based amorphous/nanocrystalline composite coating. However, the presence of cracks was detected in Fig. 7c and d, indicating the dominant wear mechanism of the coating as fatigue wear. During fatigue wear, because of the alternating load effect, the nucleation and propagation of cracks transpire along the
S.K. Nayak et al. / Journal of Alloys and Compounds 825 (2020) 154120
7
Fig. 7. (a) Wear rate (b) coefficient of friction (COF) vs. sliding distance plots acquired from dry sliding wear test (pin-on-disc) performed on the coatings and mild steel substrate, (ced) worn surface morphologies of Coating-1, (e) worn surface area of Coating-1 used for EDS mapping, and corresponding EDS mapping of (f) Fe, and (g) O element *Figure a: Ct-1, Ct-2, Ct-3, Ct-SS and MS (sub) corresponds to Coating-1, Coating-2, Coating-3, SS coating and mild steel substrate, respectively.
defective regions of the coating viz. porosity and inter-splat regions, which ultimately leads to its delamination or flaking off from the substrate, illustrated in Fig. 7d [17,35]. Besides, the generated frictional heat during the wear condition can result in oxidative wear [36]. The oxygen mapping of the worn surface of the coating implied the oxidative wear of the coating (Fig. 7g). Therefore, it can be deduced that the mechanism of wear in dry sliding condition of Fe-based amorphous/nanocrystalline coating is fatigue accompanied by oxidative wear. The wear behaviour of the composite coatings was significantly influenced by their characteristics at both nano- (phase composition) and micro-level (porosity, inter-splat boundaries). Wear resistance of composite coatings can be enhanced by the dispersion of nanocrystalline phases in the amorphous matrix, which impede the propagation of shear bands. However, the nature of the
crystalline phases (soft or hard) being flaked off from the coating as debris particle can adversely affect their tribological behaviour. The morphology and size distribution of the debris particles are also very important in this context. It is known that, the hard phases, again depending upon their surface properties, could aggravate the wear problem by causing deep grove formation, or also could act as lubricating particles after their exfoliation from the coatings; whereas, soft phases on the wear track can cause both redeposition phenomenon and adhesive mode of wear [12,37]. As discussed earlier in section 3.3 and 3.4, an increment in amorphicity along with decreased a-Fe phase content was observed upon elevating the feed rate from 15 to 30 g/min, whereas intermetallic phase content remained almost same. Thus, enhanced wear resistance of Coating-3 can be attributed to the reduced abrasion of its worn track due to presence of lower amount of softer a-Fe phase.
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Moreover, tribological characteristics of the coatings are determined by presence of porosity and inter-splat regions on microlevel, as these defects can serve as crack initiation and/or propagation points of fatigue wear or diffusion channel for oxygen atom during oxidative wear, leading to accelerated loss of material. The superior resistance to wear for Coating-3 can also be explained in terms of lowest porosity content and better inter-splat bonding. In addition, the Fe-based composite coatings in this study, exhibited lower friction coefficient, low specific wear rate, compared to the substrate as well as SS coating owing to their higher hardness. Moreover, specific wear rate of Coating-3 (9 106 mm3/Nm) is lower than those of the high Cr and Mo containing HVOF sprayed Fe-based amorphous coatings synthesized by Terajima et al. [38], Wang et al. [39] and Xie et al. [40]. The coatings prepared by Terajima et al., Wang et al. and Xie et al. manifested specific wear rate of ~ 105, ~12.4 106 and ~20 106 mm3/Nm, respectively. Therefore, the application of this composite coating on ductile substrates can be an economical and effective surface protection method under dry sliding wear condition. 4. Conclusions Economical (low Cr and no Mo) highly wear resistant Fe-based amorphous/nanocrystalline composite coatings were deposited on mild steel substrate by high velocity oxy-fuel (HVOF) spraying using water atomized amorphous/crystalline feedstock powder (Fee10Cre4Be4Pe2C, wt.%) with different powder feed rates and the following conclusions can be delineated: 1. Porosity content and the degree of crystallinity (precipitation of nanocrystalline phases) decreased with the increment in feed rate, which were associated to the HVOF shot peening effect and the reduced degree of melting of powder particles, respectively. 2. Higher hardness of the coatings with increased powder feed rate was attributed to better inter-splat bonding and lower extent of devitrification. 3. Increment in the powder feed rate resulted in lower wear volume during nano-scratch test of the coatings, which was ascribed to the reduction in volume fraction of softer nanocrystalline a-Fe phases at higher feed rate. 4. Dry sliding wear study revealed decreasing trends for both wear rate and coefficient of friction with increasing feed rate due to better inter-splat bonding and lower porosity content of the coatings. 5. Most importantly, the Fe-based composite coatings exhibited low wear volume during nano-scratch test and lower friction coefficient, low specific wear rate of dry sliding wear study, compared to the substrate as well as the SS coating. In addition, wear rate of the coating deposited at highest feed rate of 50 g/ min i.e. Coating-3 was found to be around one-fourth of that of the substrate and also one-third of that of the SS coating, implying enhanced resistance to wear for Coating-3 compared to other coatings.
Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. CRediT authorship contribution statement Sapan
K.
Nayak:
Conceptualization,
Methodology,
Investigation, Formal analysis, Data curation, Visualization, Writing - original draft. Anil Kumar: Methodology, Investigation, Formal analysis. Abhishek Pathak: Methodology. Atanu Banerjee: Methodology, Resources, Project administration. Tapas Laha: Conceptualization, Supervision, Validation, Writing - review & editing, Resources, Project administration. Acknowledgements The author, T. Laha thankfully acknowledges the financial support obtained from Research and Development Division of Tata Steel, India. References [1] C. Suryanarayana, A. Inoue, Iron-based bulk metallic glasses, Int. Mater. Rev. 58 (2012) 131e166. [2] D.H. Kwon, E.S. Park, M.Y. Huh, H.J. Kim, J.C. Bae, Wear behavior of Fe-based bulk metallic glass composites, J. Alloys Compd. 509 (2011) S105eS108. [3] D.D. Liang, X.S. Wei, C.T. Chang, J.W. Li, X.M. Wang, J. Shen, Effect of W addition on the glass forming ability and mechanical properties of Fe-based metallic glass, J. Alloys Compd. 731 (2018) 1146e1150. [4] M.F. Ashby, A.L. Greer, Metallic glasses as structural materials, Scripta Mater. 54 (2006) 321e326. [5] M. Chen, Mechanical behavior of metallic glasses: microscopic understanding of strength and ductility, Annu. Rev. Mater. Res. 38 (2008) 445e469. [6] S.F. Guo, L. Liu, N. Li, Y. Li, Fe-based bulk metallic glass matrix composite with large plasticity, Scripta Mater. 62 (2010) 329e332. [7] W. Yang, H. Liu, Y. Zhao, A. Inoue, K. Jiang, J. Huo, H. Ling, Q. Li, B. Shen, Mechanical properties and structural features of novel fe-based bulk metallic glasses with unprecedented plasticity, Sci. Rep. 4 (2014) 1e6. [8] X.J. Gu, S.J. Poon, G.J. Shiflet, Mechanical properties of iron-based bulk metallic glasses, J. Mater. Res. 22 (2007) 344e351. [9] W. Guo, Y. Wu, J. Zhang, S. Hong, G. Li, G. Ying, J. Guo, Y. Qin, Fabrication and characterization of thermal-sprayed Fe-based amorphous/nanocrystalline composite coatings: an overview, J. Therm. Spray Technol. 23 (2014) 1157e1180. [10] Y. Wang, M.Y. Li, L.L. Sun, X.Y. Zhang, J. Shen, Environmentally assisted fracture behavior of Fe-based amorphous coatings in chloride-containing solutions, J. Alloys Compd. 738 (2018) 37e48. [11] B.Y. Fu, D.Y. He, L.D. Zhao, Effect of heat treatment on the microstructure and mechanical properties of Fe-based amorphous coatings, J. Alloys Compd. 480 (2009) 422e427. [12] L. Liu, J.K. Xiao, X. Wei, Y. Ren, G. Zhang, C. Zhang, Effects of temperature and atmosphere on microstructure and tribological properties of plasma sprayed FeCrBSi coatings, J. Alloys Compd. 753 (2018) 586e594. [13] M.P. Planche, H. Liao, B. Normand, C. Coddet, Relationships between NiCrBSi particle characteristics and corresponding coating properties using different thermal spraying processes, Surf. Coating. Technol. 200 (2005) 2465e2473. [14] S. Sampath, X.Y. Jiang, J. Matejicek, L. Prchlik, A. Kulkarni, A. Vaidya, Role of thermal spray processing method on the microstructure, residual stress and properties of coatings: an integrated study of Ni-5 wt. % Al bond coats, Mater. Sci. Eng. A. 364 (2004) 216e231. [15] H.J. Kim, K.M. Lim, B.G. Seong, C.G. Park, Amorphous phase formation of Zrbased alloy coating by HVOF spraying process, J. Mater. Sci. 36 (2001) 49e54. [16] C. Zhang, L. Liu, K.C. Chan, Q. Chen, C.Y. Tang, Wear behavior of HVOF-sprayed Fe-based amorphous coatings, Intermetallics 29 (2012) 80e85. [17] Z. Zhou, L. Wang, D.Y. He, F.C. Wang, Y.B. Liu, Microstructure and wear resistance of Fe-based amorphous metallic coatings prepared by HVOF thermal spraying, J. Therm. Spray Technol. 19 (2010) 1287e1293. [18] G.Y. Koga, R. Schulz, S. Savoie, A.R.C. Nascimento, Y. Drolet, C. Bolfarini, C.S. Kiminami, W.J. Botta, Microstructure and wear behavior of Fe-based amorphous HVOF coatings produced from commercial precursors, Surf. Coating. Technol. 309 (2017) 938e944. [19] J. Li, L. Yang, H. Ma, K. Jiang, C. Chang, J.Q. Wang, Z. Song, X. Wang, R.W. Li, Improved corrosion resistance of novel Fe-based amorphous alloys, Mater. Des. 95 (2016) 225e230. [20] M. Taheri, Z. Valefi, K. Zangeneh-Madar, Influence of HVOF process parameters on microstructure and bond strength of NiCrAlY coatings, Surf. Eng. 28 (2012) 266e272. [21] B. Hausnerova, B.N. Mukund, D. Sanetrnik, Rheological properties of gas and water atomized 17-4PH stainless steel MIM feedstocks: effect of powder shape and size, Powder Technol. 312 (2017) 152e158. [22] M. Li, P.D. Christofides, Modeling and control of high-velocity oxygen-fuel (HVOF) thermal spray: a tutorial review, J. Therm. Spray Technol. 18 (2009) 753e768. [23] D. Zois, A. Lekatou, M. Vardavoulias, T. Vaimakis, A.E. Karantzalis, Partially amorphous stainless steel coatings: microstructure, annealing behavior and statistical optimization of spray parameters, Surf. Coating. Technol. 206 (2011) 1469e1483.
S.K. Nayak et al. / Journal of Alloys and Compounds 825 (2020) 154120 [24] P. Bansal, P.H. Shipway, S.B. Leen, Residual stresses in high-velocity oxy-fuel thermally sprayed coatings - modelling the effect of particle velocity and temperature during the spraying process, Acta Mater. 55 (2007) 5089e5101. [25] L. Qiao, Y. Wu, S. Hong, J. Cheng, Z. Wei, Influence of the high-velocity oxygenfuel spray parameters on the porosity and corrosion resistance of iron-based amorphous coatings, Surf. Coating. Technol. 366 (2019) 296e302. [26] Y. Wang, S.L. Jiang, Y.G. Zheng, W. Ke, W.H. Sun, X.C. Chang, W.L. Hou, J.Q. Wang, Effect of processing parameters on the microstructures and corrosion behaviour of high-velocity oxy-fuel (HVOF) sprayed Fe-based amorphous metallic coatings, Mater. Corros. 64 (2013) 801e810. [27] J. Wu, S.D. Zhang, W.H. Sun, Y. Gao, J.Q. Wang, Enhanced corrosion resistance in Fe-based amorphous coatings through eliminating Cr-depleted zones, Corrosion Sci. 136 (2018) 161e173. [28] R.S. Maurya, A. Sahu, T. Laha, Quantitative phase analysis in Al86Ni8Y6 bulk glassy alloy synthesized by consolidating mechanically alloyed amorphous powder via spark plasma sintering, Mater. Des. 93 (2016) 96e103. [29] Y.Y. Sun, M. Song, X.Z. Liao, G. Sha, Y.H. He, Effects of isothermal annealing on the microstructures and mechanical properties of a FeCuSiBAl amorphous alloy, Mater. Sci. Eng. A. 543 (2012) 145e151. [30] A. Kumar, R. Kumar, P. Bijalwan, M. Dutta, A. Banerjee, T. Laha, Fe-based amorphous/nanocrystalline composite coating by plasma spraying: effect of heat input on morphology, phase evolution and mechanical properties, J. Alloys Compd. 771 (2019) 827e837. [31] A. Agarwal, N.B. Dahotre, Mechanical properties of laser-deposited composite boride coating using nanoindentation, Metall. Mater. Trans. A Phys. Metall. Mater. Sci. 31 (2000) 401e408. [32] D.M. Mini c, A. Mari ci c, B. Adnadevi c, Crystallization of a-Fe phase in amorphous Fe81B13Si4C2 alloy, J. Alloys Compd. 473 (2009) 363e367.
9
[33] A. Loganathan, A. Sahu, C. Rudolf, C. Zhang, S. Rengifo, T. Laha, B. Boesl, A. Agarwal, Multi-scale tribological and nanomechanical behavior of cold sprayed Ti2AlC MAX phase coating, Surf. Coating. Technol. 334 (2018) 384e393. [34] K. Balani, S.P. Harimkar, A. Keshri, Y. Chen, N.B. Dahotre, A. Agarwal, Multiscale wear of plasma-sprayed carbon-nanotube-reinforced aluminum oxide nanocomposite coating, Acta Mater. 56 (2008) 5984e5994. [35] J.B. Cheng, X.B. Liang, Z.H. Wang, B.S. Xu, Dry sliding friction and wear properties of metallic glass coating and martensite stainless coating, Tribol. Int. 60 (2013) 140e146. [36] L. Xie, X. Xiong, Y. Zeng, Y. Wang, The wear properties and mechanism of detonation sprayed iron-based amorphous coating, Surf. Coating. Technol. 366 (2019) 146e155. [37] C. Si, B. Duan, Q. Zhang, J. Cai, W. Wu, Microstructure, corrosion-resistance, and wear-resistance properties of subsonic flame sprayed amorphous Fe e Mo e Cr e Co coating with extremely high amorphous rate, J. Mater. Res. Technol. (2020) 1e12. [38] T. Terajima, F. Takeuchi, K. Nakata, S. Adachi, K. Nakashima, T. Igarashi, Composite coating containing WC/12Co cermet and Fe-based metallic glass deposited by high-velocity oxygen fuel spraying, J. Alloys Compd. 504S (2010) S288eS291. [39] W. Wang, C. Zhang, P. Xu, M. Yasir, L. Liu, Enhancement of oxidation and wear resistance of Fe-based amorphous coatings by surface modification of feedstock powders, Mater. Des. 73 (2015) 35e41. [40] L. Xie, Y.M. Wang, X. Xiong, Z.K. Chen, Comparison of microstructure and tribological properties of plasma, high velocity oxy-fuel and detonation sprayed coatings from an iron-based powder, Mater. Trans. 59 (2018) 1591e1595.