Fretting Wear Resistance Research Articles

Dependence of fretting wear resistance on the α morphology and stress-induced martensite transformation in a metastable β titanium alloy

Systematic experimental investigations concerning the influence of α morphology on the fretting wear behaviors of metastable β titanium alloys are carried out. A Ti-10V-2Fe-3Al titanium alloy was subjected to different heat treatment routes to create dual phase microstructures consisted of β phase plus α phase with three different morphologies. The effect of α morphology on the fretting wear resistance, the resulting failure mechanisms, and stress induced martensite transformation (SIMT) were unraveled. Results show that the α morphology has a significant influence on fretting wear behaviors depending on the fretting run regimes. In the partial slip regime (PSR) and mixed fretting regime (MFR), the microstructure with lath α morphology has a lowest fretting wear volume accompanied by relatively strong SIMT effect. While in gloss slip regime (GSR), the globular α microstructure has a lowest fretting wear volume along with strongest SIMT response, yet a highest fretting wear volume for the acicular α morphology microstructure due to its brittleness nature. The subsurface observations demonstrates that a compacted and thick plastic deformation layer, especially for the mechanical mixture layer, can well protect the material surface against the fretting wear damage.

Effect of laser remelting on microstructure evolution and high-temperature fretting wear resistance in a laser-cladding self-lubricating composite coating on titanium alloy substrate

TC21 titanium alloy possesses the advantage including high strength, low density, and great resistance to damage. Combining it with surface modification technology, it is expected to improve the performance of aviation structural components. This work applied laser remelting technology to realize surface modification, and the hardness and fretting wear properties of the coating were investigated. This research has found that laser remelting technology can effectively refine grain size and improve the performance of coatings. By exploring different laser remelting powers (600 W, 900 W, 1200 W) and the different diameters of laser beam (3 mm, 6 mm), the optimal laser process was obtained with laser power and spot diameter of 600 W and 6 mm, respectively. The average grain size is 2.1 μm. The laser remelting coating has an average microhardness about 980 HV0.2, and it is 2.5 times and 1.3 times higher than the substrate and laser cladding hardness, respectively. A minimum coefficient of friction (COF) about 0.5 was obtained by the laser remelting coating, and the wear rate reaches the lowest of 1.87 × 10−6 mm3/(N·m) at fretting temperature with 500 °C. The abrasive wear and adhesive wear were the main wear mechanisms, and accompanied by oxidative wear. This study provides important reference for improving the performance of high-strength titanium alloy to obtain low defect, high-performance coatings with stable quality.

Exploring ambient and elevated temperature fretting wear behavior of laser-cladding (FeCrCoNi)84AlxNby high-entropy alloy coatings

In this work, (FeCrCoNi)84AlxNby (x = 12, 8, 4 and y = 4, 8, 12 (at. %)) high-entropy alloy (HEA) coatings were successfully deposited on 316 stainless steel via laser cladding (LC). FCC/BCC + Laves structure was introduced into FeCrCoNi HEA system by designing different Al/Nb ratios, aiming to improve the fretting wear resistance. The phase constituents, microstructure, and fretting wear resistance of (FeCrCoNi)84AlxNby HEA coatings at ambient temperature and 285 °C were respectively analyzed. Results confirmed that the microstructure of three HEA coatings displayed the interdendritic (IR) - dendritic (DR) structure. With the Al/Nb ratio decreased from 3/1 to 1/3, the phase constituents of HEA coatings transformed from the BCC solution to FCC solution and Laves phase, and the content of the Laves phase gradually increased. Moreover, the average grain size decreased from 16.9 μm to 4.6 μm, while the average geometrically necessary dislocations (GNDs) density increased from 1.842 × 1010 m−2 to 2.821 × 1010 m−2. The microhardness of the HEA coatings was improved from 210 HV0.2 to 361–647 HV0.2 compared with that of the substrate. The decrement of Al/Nb ratio improved the fretting wear resistance of HEA coatings both at ambient temperature and 285 °C, especially at 285 °C. The wear volume decreased from 0.8 × 105 μm3 to 0.39 × 105 μm3 and the fretting wear mechanism changed from severe fatigue wear to slight abrasive wear at 285 °C. In the Al4Nb12 HEA coating, the soft structure (FCC) and the hard structure (Laves) were combined into a wear-resistant skeleton, and the Laves structure was massively distributed along the FCC phase to prevent the FCC phase from further slipping in the fretting wear process, which in turn minimizes the fretting damage. The present work provides a theoretical basis for the related research on the fretting wear characteristics of laser cladding HEA coatings.

Effect of laser energy on the fretting wear resistance of femtosecond laser shock peened Ti6Al4V

Femtosecond laser shock peening (FsLSP) is performed on engineering alloys to improve their wear resistance in dry and oil-lubricated sliding conditions. In this study, the influence of FsLSP on the fretting wear behavior of Ti6Al4V alloy is studied. For this purpose, FsLSP treatment, with laser energies of 50, 100, 150, and 200 μJ, is performed on a Ti6Al4V sample which mainly consists of α-phase. Topographical investigations using white light interferometry reveal that with increase in the laser energy, the coverage area of laser-induced periodic surface structures (LIPSSs) decreases, and the extent of surface pitting damage increases, leading to higher surface roughness. While surface hardness also initially increases with increasing laser energy, it remains invariant when the energy is increased beyond 150 μJ. Sub-surface microstructural investigations and kernel average misorientation maps obtained from electron backscatter diffraction reveal that FsLSP treatment leads to the formation of severely deformed and mildly deformed layers along the depth of the alloy surface. Surface hardening due to FsLSP is attributed to the activation of prismatic <a>, basal <a> slip systems, and 101¯2, 112¯3 tensile twins in the severely deformed zone along with grain refinement, which is an outcome of dynamic recrystallization. Fretting wear tests indicate that the coefficient of friction (CoF) of FsLSP treated alloys is consistently lesser than that of its as-received counterpart, whose CoF is 0.38. In contrast, the wear resistance, quantified by the wear rate, wear volume and wear depth, is highest in the sample treated with laser energy of 100 μJ but lower for the as-received as well as 150 and 200 μJ laser treated samples. These results are explained on the basis of the differences in the contact area, formation of surface hardening layer and the size and integrity of asperities on the surface, which in turn influences the dominant fretting wear mechanism.

High-temperature fretting wear behavior and microstructure stability of a laser-cladding Ti-Al-C-N composite coating meditated by variable cycle conditions

Ti-6Al-4 V titanium alloy is used for low-pressure compressor blades of aero-engine due to its high specific strength, excellent corrosion resistance and high-temperature stability. Low-pressure compressor blades are subject to fretting wear in service, which may lead to fracture failure of the blades. The preparation of wear-resistant coatings is currently an effective solution in solving the problem of fretting wear on Ti-6Al-4 V titanium alloy. However, the fretting wear resistance and microstructure stability of the coating under variable cycle fretting conditions require more attention. In this work, the fretting wear performance and microstructure stability of the Ti-Al-C-N composite coating under variable cycle fretting conditions are investigated. The results show that the parameters of variable cycle operating conditions have a notable effect on the coefficient of friction (COF). The variable frequency and variable temperature working conditions result in the alteration of the fretting operation mechanism. Whereas the variable stroke amplitude and the variable load conditions do not cause changes in the fretting operation mechanism, and both are in the gross slip region (GSR). The lowest wear rate occurs under variable stroke amplitude conditions. The wear rate is the maximum under the variable cycle temperature condition. According to the dissipated energy calculation, the difference between the two different stroke amplitudes is the biggest among all the conditions. EBSD and TEM analyses show that the subsurface of variable stroke amplitude worn scar has a more uniform strain distribution, and reveals a unique subsurface structure with a transformation from crystalline to amorphous, which contributes to improving the wear resistance. This work provides insights into coating microstructure stability and wear mechanisms under variable cycle conditions.

Improved mechanical and fretting wear behaviour of Stir-Cast AA7075 composites reinforced with hexagonally ordered MoS2 and SiC

In this study, three different types of hybrid composites were developed using AA7075, MoS₂, and SiC through a stir-casting process. The first composite was reinforced with MoS₂/SiC at 5/10 wt%. The second was reinforced with MoS₂/SiC at 7.5/7.5 wt% and the third with MoS₂/SiC at 10/5 wt%. Both reinforcements exhibited hexagonal structures at the casting temperature. The refined grains led to improved mechanical and fretting wear properties. For the composite with MoS₂/SiC at 10/5 wt%, fretting wear resistance was enhanced compared to the other samples. An average coefficient of friction of 0.471 was obtained for the MoS₂/SiC 10/5 wt% sample. XRD results revealed the presence of various phases, including Al12Mo.

Tribological and mechanical properties improvement of G20CrNiMo alloy via fabricating gradient composite layer through ultrasonic strengthening grinding process

Fretting wear is one of the main causes of damage failure at the contact interface, which significantly limits the reliable application of mechanical parts. To address this issue, a composite microstructure comprising a gradient structure, α-Al2O3 particles, and micro-dimples was fabricated on the G20CrNiMo alloy by an improved method of ultrasonic strengthening grinding process (USGP). Subsequently, the fretting resistance and mechanical properties of the treated G20CrNiMo alloy were investigated. The results indicated that USGP could significantly enhance mechanical strength and wear resistance properties. The USGP-treated sample demonstrated an increment of approximately 25.32 % in tensile strength compared to the untreated sample. It also exhibited reductions of about 19.61 % and 49.56 % in friction coefficient and wear volume, respectively. After USGP treatment, the gradient structure incorporating dense dislocation and high-angle grain boundaries (HAGBs) limited the shear motion of the G20CrNiMo alloy, thereby enhancing its mechanical properties. Furthermore, the synergistic effect of gradient structure, Al2O3 particles, and micro-dimples effectively restricted shear deformation and formed a supplementary glaze to further improve its fretting wear resistance.

Subsurface deformation mechanism and the interplay relationship between strength-ductility and fretting wear resistance during fretting of a high-strength titanium alloy

Fretting wear damage of high-strength titanium fasteners has caused a large number of disastrous accidents. Traditionally, it is believed that both high strength and excellent ductility can reduce fretting wear damage. However, whether strength and ductility are contradictory or not and their appropriate matching strategy under the external applied normal stress (Fw) are still confusing problems. Here, by analyzing the subsurface-microstructure deformation mechanism of several samples containing various α precipitate features, for the first time, we design strategies to improve fretting damage resistance under different matching relation between Fw and the tensile strength of materials (Rm). It is found that when Fw is greater than Rm or Fw is nearly equivalent to Rm, the deformation mechanism mainly manifests as serious grain fragmentation of β and αGB constituents. Homogeneous deformation in large areas only reduces damage to a limited extent. It is crucial to improve the strength to resist cracking and wear, but it is of little significance to improve the ductility. However, when Fw is far less than Rm, coordinated deformation ability reflected by ductility plays a more important role. The deformation mechanism mainly manifests as localized deformation of β and αGB constituents (kinking induced by twinning and spheroidizing). A unique composite structure of nano-grained/lamellar layer and localized deformation transition layer reduces fretting damage by five times compared with a single nano-grained layer. Only when the strength is great enough, improving the plasticity can reduce wear. This study can provide a principle for designing fretting damage resistant alloys.

Enhancing high-temperature fretting wear resistance of Ti-64 alloy by laser cladding FeCrAlMoxNby high entropy alloy coatings

Fretting wear is the main factor restricting the application of titanium alloy as compressor blades. Preparing a kind of high entropy alloy (HEA) coating is an effective way to improve the fretting wear resistance under high temperature conditions. Thus, in the present work, the FeCrAlMoxNby HEA coating was fabricated on a Ti-64 substrate by the laser cladding technology. The phase composition, microstructure and fretting wear resistance of the coating at high temperatures (200 °C, 300 °C and 400 °C) were investigated. It was demonstrated that the laser cladding FeCrAlMoxNby HEA coatings exhibited dense and uniform microstructures consisting of a BCC phase and a Laves phase (Cr2Nb). In addition, the changing trend of phase content of BCC and Laves phase is the same as the trend of atomic content of Mo and Nb respectively. The presence of the Laves phase increases the hardness of the coating. Due to its high hardness and the formation of a protective oxide layer, the coating demonstrated significantly superior resistance to high-temperature fretting wear compared to the substrate. The lowest wear rate is Mo0·5Nb0.5 coating at 300 °C, only 1.3 × 10−6 mm3/N·m. The current results provide a new method to protect titanium alloy's surface from fretting wear damage in high-temperature service environments.

Effect of the APS YAG coating on the fretting wear properties of Ti60 titanium alloy

To enhance the fretting wear resistance of Ti60 titanium alloy, a YAG coating was applied to the surface using the APS (atmospheric plasma spray) process, followed by an investigation of its fretting wear performance. Nanoindentation technology was employed to evaluate nanomechanical properties, and subsequently, techniques including SEM, EDS, TEM, XRD, XPS, and laser confocal microscopy were utilized to characterize microstructural features of the wear marks and the composition of wear debris. The results indicated that, owing to the presence of the APS YAG coating, the surface nanohardness of the Ti60 titanium alloy increased from 4.4 GPa to 11.06 GPa, while the fretting friction coefficient decreased from 0.186 to 0.155, and the volume wear is reduced by 80.53 %, which significantly improves the fretting wear resistance of Ti60 titanium alloy. As the number of fretting cycles increased, a complete friction layer formed on the surface of the Ti60 titanium alloy, leading to a decrease in fretting friction coefficient and a shift in the wear mechanism. Ultimately, a mixed mechanism was observed involving oxidative wear, abrasive wear, fatigue-induced peeling of the friction layer, and localized plastic deformation. Conversely, the fretting wear mechanism of the APS YAG coating consistently demonstrated abrasive wear, adhesive wear, and fatigue-induced cracking and spalling of the coating.

Revealing fretting wear resistance mechanism under liquid lead-bismuth eutectic of Cr-Al-C composite coatings fabricated by laser cladding

Laser cladding technology was utilized to construct protective coatings on the surfaces of service materials and to study the mechanical and fretting wear properties of the coatings. The coating mainly consists of diffuse Cr2AlC phase, interdendritic Cr7C3 phase and dendritic Cr-based solid solution. The hardness of the coating was enhanced to 690 HV, which is 3.1 times higher than the hardness of the substrate. The change in H3/Er2 values of the coating and the substrate were calculated by nanoindentation to be 0.04 and 0.024, respectively, and the anti-fretting wear properties of the coating was excellent. The statistical distribution of the Schmidt factor of the coatings is between 0.41 and 0.5, which indicates that the coatings have a high probability of initiating slip and high plastic deformation capacity. For those grains with large Schmidt factors, dislocations can be easily activated in response to applied stresses. Strength is the first element of wear resistance, and with sufficiently high strength, the plasticity enhancement can be very effective in improving the fretting damage resistance. After the fretting wear test in liquid LBE, the Cr-Al-C composite coating has a huge increase in wear resistance compared to the substrate. The wear resistance of the coating was 33 times that of the 316 stainless steel substrate at a test temperature of 450 °C

Effect of laser shock peening on cylinder-on-flat torsional fretting wear resistance performance of titanium alloy

Torsional fretting wear is a commonly wear form in assemblies, while its inherent concealment and debris evolution make it difficult to study. Titanium alloy, widely used in aviation and aerospace, suffer from fretting wear under complex alternating load. In this paper, the effects of laser shock peening (LSP), fretting amplitude, and frequency on cylinder-on-flat torsional fretting wear of TC21 alloy was investigated. The friction torque and fretting loop were illustrated to identify the fretting regime. Results shown that LSP reconstructed surface morphology, increased surface roughness and hardness, meanwhile reduced the wear volume of titanium by more than 30 %. The fretting wear mechanisms varied with amplitude: lower amplitudes led to oxidation and adhesive wear, while higher amplitudes caused oxidation and abrasive wear. The results of wear volume shown that the influence of fretting frequency on wear was related to the difficulty of wear debris discharge.

Abnormal fretting wear behavior of Fe-based amorphous coating

To promote the application of Fe-based amorphous coating (AMC)-protected magnesium alloys in fretting wear conditions, a Fe-based AMC with a thickness of about 164 μm was deposited on AZ31B magnesium alloy substrate by detonation spraying. The microstructure and fretting wear behaviors against GCr15 counterpart ball in different frequencies of the Fe-based AMC were studied in detail. The results show that the Fe-based AMC has a substantially complete amorphous structure, the porosity and surface hardness are ≤1.2 vol %, and 764.7 ± 37.5 Hv0.1, respectively. Therefore, the Fe-based AMC presents excellent fretting wear resistance, and its wear rate is almost 1/10 of that of AZ31B magnesium alloy, and 1/5 of that of high-velocity oxygen-fuel sprayed 316L stainless steel coating on AZ31B magnesium alloy substrate. The fretting wear behavior of Fe-based AMC was found to be sensitive to the fretting frequency: as the frequency increases from 5 to 100 Hz, the average steady-state friction coefficient increases from 0.77 to 1.07, but the wear rate exhibits an anomalous phenomenon, decreasing from 5.26 × 10−5 mm3N−1m−1 to 3.47 × 10−5 mm3N−1m−1. The improvement in wear rate is mainly attributed to the formation of an oxygen-rich river-like friction layer on the worn surface as the transient contact temperature increases with frequency, effectively suppressing delamination wear. Additionally, the occurrence of high transient frictional temperatures at high frequencies leads to evident crystallization within the coating, accompanied by the formation of nanocrystals, oxide films, and a large area river-like friction layer consisting of debris-compacted layers, which strengthens the Fe-based AMC. Consequently, the wear mechanism changes from delamination wear and abrasive wear at low frequencies to oxidative wear and adhesive wear at high frequencies, resulting in superior fretting wear resistance of the Fe-based AMC at high frequencies.

The oil lubricated fretting wear behavior under different sliding displacements and frequencies of Ti6Al4V titanium alloy as affected by micro-shot peening

The fretting wear behavior under oil lubricants is of great practical significance since oil is usually used to regulate fretting regime for minimizing wear. In this study, micro-shot peening (MSP) was performed on Ti6Al4V titanium alloy, in which 0.6 MPa injection air pressure, 60 s shot time and high-speed steel particles with an average diameter of 50 μm were used. Surface topography, microstructure, hardness and compression residual stress of test samples were examined. Oil lubricated fretting wear tests were then conducted between titanium alloy sample and GCr15 counterbody under different sliding displacements and frequencies. The test results show that the surface structure of MSP treated samples experienced severe plastic deformation, the surface hardness was increased from 310.8 HV to 433.5 HV, and a compression residual stress of −303.5 MPa was introduced within surface layer. Moreover, MSP treatment reduced the coefficients of friction through producing a micro-dimpled surface. Thereby, the fretting wear resistance of MSP treated sample under oil lubricated condition was improved. By comparison, at higher sliding displacement and frequency, the ability of MSP treatment to resist fretting wear was improved more significantly since more better lubricating effect can be obtained. Fretting damage of untreated sample under oil lubrication was mainly attributed to fatigue wear, delamination wear, abrasive wear and oxidation wear, while that of MSP treated sample was mainly regional peeling off and abrasive wear.

Study on Fretting Wear Properties of GCr15 Steel Via Ultrasonic Surface Rolling Process

Abstract Ultrasonic surface rolling (USR) was applied to GCr15 steel with different static loads and passes to improve the friction and wear properties, and then the fretting wear mechanism of GCr15 steel after USR treatment was systematically investigated. The results showed that the specimens treated by the USR had lower surface roughness and significantly increased compressive residual stress and microhardness. Furthermore, severe plastic deformation occurred in the surface layer of the specimen, which refined the grains and increased the density of high- and low-angle grain boundaries. Besides, the results of the fretting test showed that the USR treated specimens had lower wear volume, dissipated energy, and steady-state friction coefficient. The fretting wear resistance increased with the static load and the number of passes. The fretting wear mechanism changed from abrasive wear and severe adhesive wear to slight fatigue wear and abrasive wear owing to the use of the USR treatment. Surface smoothing and hardening are responsible for the improvement in the fretting wear properties of GCr15 steel for USR treatment.

Effect of rolling-texture intensity on fretting damage and subsurface deformation behavior in a high-strength titanium alloy

Fretting damage is common in the high-strength titanium alloy fastener widely used in the aeronautic industry, leading to the failure of fastening fit or the initiation of crack. The titanium alloy fasteners often have typical preferred orientation characteristics (i.e., texture), and this is one of the important factors affecting its performance. However, the investigations on the mechanism of β rolling-texture intensity on fretting damage resistance and subsurface deformation are less addressed. Hence, fretting wear tests were carried out on samples with different rolling texture intensities. The results demonstrate that the samples with quite low (A-10 % sample) and quite high (D-70 % sample) rolling-texture intensity both exhibit excellent fretting wear resistance, but their mechanisms are completely different. Uniformly dispersed grain orientation renders the A-10 % sample with good recovery ability and a positive friction effect during wear. Low stress only concentrating at grain boundaries (GBs) weakens cracks’ initiation and propagation. The unique orientation-layered structure (OLS) leads to excellent recovery ability and a positive friction effect. Crack propagation is inhibited and only propagates along the OLS boundary without a connected trend. However, samples with moderate rolling texture intensity exhibit severe wear. Dislocations are restricted in local areas, so the poor recovery ability makes them have a negative friction effect. Crack propagation driving force continuously increases. Appropriate rolling texture intensity can reduce wear by three times. This study can provide information on the principle for designing fretting damage-resistant alloys.

Synergistic mechanism of the fretting wear resistance of Fe2O3/Ag nanostructured coatings prepared by sliding friction and magnetron sputtering

The synergistic effect of the hard/soft phases of a material is potentially valuable and significant for improving wear resistance. Given this, a method for preparing Fe2O3/Ag nanostructured coatings, in which reciprocating sliding friction is used to prepare nano-Fe2O3 coatings and magnetron sputtering is used to prepare nano-Ag coatings, is proposed. The fretting wear test using a SiC ball as the friction pair shows that a large amount of oxide accumulates on the friction pair surface of the substrate, while that of the coating is smooth, and the coating greatly improves the wear resistance of the sample. In particular, the Fe2O3/Ag coating has better fretting wear resistance, and the wear rate is as low as 7.03 × 10−6 μm3N−1μm−1. The excellent tribological properties of Fe2O3/Ag nanostructured coatings at room temperature are derived from the Ag–Fe2O3 nanocomposite layer with a Ag composition gradient, which is formed by Ag nanoparticles gradually penetrating into the Fe2O3 layer under the normal load produced during fretting wear. Furthermore, the Ag/Fe2O3 semi-coherent interface, which is induced between Ag and Fe2O3 nanoparticles under fretting wear, endows the composite layer with excellent thermal and mechanical stability. This design idea of using a fretting wear load to prepare composite coatings with the synergistic effect of hard and soft phases to strengthen the wear performance of a workpiece also provides a reference for the preparation of other hard/soft heterogeneous coatings.

Tribological Properties of γ-TiAl Alloy Fretting against Nickel-Based Superalloy at Elevated Temperature

The tribological properties of γ-TiAl alloys under sliding condition have been well established, but the mechanisms for fretting wear, especially at elevated temperature, remain to be further clarified. In the present study, the tribological behaviors and mechanisms of a γ-TiAl alloy were investigated under an elevated temperature fretting condition. The wear scars, debris, and tribolayers were studied with scanning electron microscope, energy dispersive spectrometer, and Raman spectrometer. The structural and mechanical properties of the tribolayers were investigated utilizing transmission electron microscope and nanoindentation tests. The results demonstrated that the severe adhesive wear, delamination, and abrasive wear in the early stage of fretting resulted in high wear rate of the γ-TiAl alloy. As fretting progresses, the formation of tribolayers with nanograins and excellent mechanical properties improved the fretting wear resistance of the γ-TiAl alloy. Due to the protective effect of the adhesively transferred γ-TiAl, the wear rate of the nickel-based superalloy counterpart was significantly lower.

Role of temperature in tribolayers in fretting wear of γ-TiAl alloy

The formation of tribolayers may play significant influences on fretting wear. At elevated temperature, the adhesion among wear debris and the increased diffusion rate facilitate the formation of tribolayers. However, the intensification of oxidation at elevated temperature and the low diffusion rate in oxides may play an adverse role. The present study aims to investigate the role of temperature in tribolayers in fretting wear using a γ-TiAl alloy. Scanning electron microscope, energy dispersive spectrometer, Raman spectrometer, transmission electron microscope and nanoindentation were utilized to investigate the wear debris, tribolayers, and wear scars. The fretting tests showed that, compared with that at room temperature (RT) and 350 °C, significant reduction in wear rate and decrease in the fluctuation of friction coefficient occurred at 550 and 750 °C. It was further revealed that when temperature raised from room temperature (RT) to 750 °C, the oxidation of the wear debris increased slightly and the diffusion coefficients increased prominently, which facilities the formation of well tribo-sintered tribolayers. The well tribo-sintered tribolayers presented homogenous structure, nanocrystalline grains with excellent mechanical properties, and resulted in the improvement in the fretting wear resistance of the γ-TiAl alloy at 550 and 750 °C.

Microstructures and properties of FeCrAlMoSix high entropy alloy coatings prepared by laser cladding on a titanium alloy substrate

By laser cladding, a FeCrAlMoSix high entropy alloy (HEA) coating (x = 0, 0.05, and 0.10) was produced on Ti6Al4V titanium alloy surface to improve its resistance to the influence of high-temperature fretting wear on Ti6Al4V. The mechanical characteristics, phase composition, and fretting wear resistance of the coating were examined at RT and 400 °C. The findings show that the FeCrAlMoSix coating is made up of a B2 phase and an intermetallic compound μ phase. At RT and 400 °C, increasing the Si concentration significantly enhanced the coating's microhardness. At x = 0.10, the average microhardness of the coated surface was 805 HV, and grain refinement and increase in μ phase were the reasons for the improvement of microhardness. The fretting wear experiment shows that the coating system can reduce wear loss and COF. In addition, at RT and high temperature, increasing the Si element can considerably improve the coating's resistance to fretting wear. However, due to stress concentration, too much μ phase may increase the risk of microcracking in the coating. This work provides a potential method for improving the protection against fretting wear damage on the titanium alloys' surface.