Browsing by Author "Preetham Kumar, G.V."

Now showing 1 - 20 of 23

Dry sliding wear behaviour of Al-5Zn-2Mg alloy processed by severe plastic deformation
(Elsevier Ltd, 2019) Manjunath, G.K.; Udaya Bhat, K.; Preetham Kumar, G.V.
Equal channel angular extrusion/pressing (ECAE/P) is an effectual technique to raise the mechanical, physical properties and resistance to wear of the materials. In this research, Al-5Zn-2Mg alloy material was ECAPed in route BC at lowest temperature. Hardness of the test material was increased after ECAE/P due to microstructure refinement. To demonstrate the wear characteristics of the Al-5Zn-2Mg alloy material after ECAE/P, wear tests (in dry sliding condition) were conducted at 2 conditions (condition 1: 19.62 N load and 1 m/s sliding speed, condition 2: 39.24 N load and 2 m/s sliding speed). The wear rate and magnitude of coefficient of friction (Î¼) were lessened after ECAE/P. Abrasive, adhesive and oxidation wear mechanisms are the predominant wear mechanisms noticed in the ECAE/P processed billets. Along with these mechanisms relocation of iron elements from the counter body (disc) to the test material was noticed. Â© 2019 Elsevier Ltd.
Effect of equal channel angular pressing on the microstructure and mechanical properties of Al-10Zn-2Mg alloy
(American Institute of Physics Inc. subs@aip.org, 2018) Manjunath, G.K.; Preetham Kumar, G.V.; Bhat, K.U.
The current investigation is focused on evaluating the mechanical properties and the microstructure of cast Al-10Zn-2Mg alloy processed through equal channel angular pressing (ECAP). The ECAP processing was attempted at minimum possible processing temperature. Microstructural characterization was carried out in optical microscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffraction analysis. Hardness measurement and tensile tests were employed to estimate the mechanical properties. Experimental results showed that, ECAP processing leads to noticeable grain refinement in the alloy. Reasonable amount of dislocations were observed in the ECAP processed material. After ECAP processing, precipitates nucleation in the material was detected in the XRD analysis. ECAP leads to considerable enhancement in the mechanical properties of the material. After ECAP processing, microhardness of the material is increased from 144 Hv to 216 Hv. Also, after ECAP processing the UTS of the material is increased from 140 MPa to 302 MPa. The increase in the mechanical properties of the alloy after ECAP processing is due to the dislocation strengthening and grain refinement strengthening. Finally, fracture surface morphology of the tensile test samples also studied. Â© 2018 Author(s).
Effect of grain refinement on material properties of Mg-8%Al-0.5%Zn alloy after the combined processes of multi-direction forging and equal channel angular pressing
(Institute of Physics, 2019) Naik, G.M.; Anjan, B.N.; Narendranath, S.; S Satheesh Kumar, S.; Preetham Kumar, G.V.
Establishing the novel microstructure is an effective method to accelerate the applications of magnesium and its alloys. In this work, an Mg-8%Al-0.5%Zn alloy (AZ80 Mg) with ultra-fine-grain (UFG) size of ?1.29 ?m was achieved by the combined processes of multi-directional forging (MDF) and equal channel angular pressing (ECAP). The achieved ultra-fine grain structure made the Mg alloy, owing to inclusive performance as the structural material. The AZ80 Mg alloy with MDF 6 pass followed by two pass ECAP has superior mechanical properties such as ultimate tensile strength (UTS) of 352 MPa and elongation of 11% when compared to as-received Mg alloy. Also, an unprocessed Mg alloy showed the corrosion rate of a 13.28 mm y?1, the corrosion rate of processed Mg alloy could be further decelerated through a change of microstructure obtained from combined processes of MDF and ECAP. This study outstandingly obtained a 94% reduction of corrosion rate after MDF-3P followed by an ECAP-2P (0.77 mm y?1) process compared to as-received Mg alloy. © 2019 IOP Publishing Ltd.
Effect of multi directional forging on impression creep behavior of Zn-24Al-2Cu alloy
(Elsevier Ltd, 2018) Sharath, P.C.; Rajendra Udupa, K.; Preetham Kumar, G.V.
Multi directional forging (MDF) of Zn-24Al-2Cu alloy were carried at 100Â°C and 200Â°C with total equivalent strain of 0.6 and 1.2 respectively. The average grain size was reduced from 30 to 1 Î¼m after MDF processing. Impression creep behavior of MDF processed samples was studied at 2 kg and 2.5 kg load with temperatures 30, 50, 100 and 150Â°C. Microstructural characterizations were carried out using optical microscope, transmission electron microscope and X-Ray diffractometer. Steady state creep rate values were recorded in the range of 1.2x10-5 to 5.2x10-7. The four phase transformation occurred in the structure after MDF process and during the impression creep test. Initial stress exponent (n) values are in the range of 2.5 to greater than 5. High values of 'n' showed due to the existence of threshold stress. The true activation energy values calculated are in the range of 22-129 kJ/mol. Changes in creep properties of MDF processed samples seem to be more sensitive to change in temperature compared to microstructural differences. Lattice diffusion controlled by dislocation climb is the dominant creep mechanism. Â© 2018 Elsevier Ltd. All rights reserved.
Effect of Multi Directional Forging on the Microstructure and Mechanical Properties of Zn-24 wt% Al-2 wt% Cu Alloy
(Springer India sanjiv.goswami@springer.co.in, 2017) Sharath, P.C.; Udupa, K.R.; Preetham Kumar, G.V.
Multi directional forging is an important process for producing fine grains in bulk materials by means of severe plastic deformation. Zn-Al alloy is used for making sleeves of plain bearings, but the presence of porosity degrades its usage in industrial application. In the present investigation, multi directional forging of Zn-24Al-2Cu alloy was carried out at 100 and 200 °C up to total strain of 0.6 and 1.2 respectively. Mechanical properties and microstructural characterization were carried out on the processed material. It was inferred that processing at 100 °C up to three passes increased ultimate tensile strength from 185 to 267 MPa with ductility of 14 %. The average grain size was reduced from 30 to 2 µm. In the case of samples processed at 200 °C up to six passes, the average grain size was reduced to 1 µm. The ultimate tensile strength increased to 276 MPa and ductility significantly improved to 21 %. The strength of the processed material increased due to strain hardening and grain refinement. Uniform distribution of various dispersed phases contributed to the enhancement of ductility during multi directional forging at 200 °C. Analysis of the fractured surface of the tensile samples revealed highly ductile nature of the fracture. © 2016, The Indian Institute of Metals - IIM.
Effect of SiC Reinforcement on Microstructure and Mechanical Properties of Aluminum Metal Matrix Composite
(Institute of Physics Publishing helen.craven@iop.org, 2018) Ajagol, P.; Anjan, B.N.; Marigoudar, R.N.; Preetham Kumar, G.V.
Aluminum reinforced with silicon carbide composites areextensively used in automobile industries and aerospaceowing to their favourable microstructure and improved mechanical behaviour with respect to pure aluminium but at a lower cost. Aluminium is remarkable for the low density and its ability to resist corrosion. The aim of present study istoevaluate the mechanical and microstructural properties of aluminum with silicon carbide (average particle size 30-45Î¼m) reinforced in varying weight percentages (wt %) ranging from 0-15 wt% in a step of 5% each. Ultimate tensile strength, micro hardness and density of the fabricated composites were investigated as a function of varying SiC wt%. Microstructure analysis was carried out on casted composites using optical microscopy and scanning electron microscopy. From micrographs it is clear that fair distribution of reinforcing particles in the matrix and also observed some clustering and porosity in the cast material. Results revealed that, the addition of SiC reinforcement in the aluminum matrix increases the hardness and ultimate tensile strength gradually from 23 HV to 47 HV and 84 MPa to 130 MPa respectively. Â© Published under licence by IOP Publishing Ltd.
Effect of zinc content on the microstructure and mechanical properties of Al-Zn-Mg alloy
(Elsevier Ltd, 2022) Manjunath, G.K.; Udaya Bhat, K.; Preetham Kumar, G.V.
In the present work, Aluminium-Zinc-Magnesium alloys (5 wt%, 10 wt% and 15 wt% Zinc and 2 wt% Magnesium) were prepared by casting process in a metal die. After casting process, heat treatment was conducted to the prepared alloys. To study the consequence of Zinc on the prepared alloys microstructure and mechanical properties were investigated. In as-cast state, in all three compositions, dendrite formation was noticed. While, after homogenization heat treatment, grain boundaries were noticed. Rise in the Zinc in the material leads to enhance the secondary particles. Microhardness and tension experiments were conducted to investigate the mechanical properties. Rise in the Zinc in the material leads to enhance the microhardness and tension strength. But ductility of the material declined with rise in the Zinc in the material. © 2021
Evolution of Tribological Properties of Cast Alâ€“10Znâ€“2Mg Alloy Subjected to Severe Plastic Deformation
(Springer Science and Business Media Deutschland GmbH, 2020) Manjunath, G.K.; Preetham Kumar, G.V.; Udaya Bhat, K.
In the current investigation, tribological behaviour of the cast Alâ€“10Znâ€“2Mg alloy processed by severe plastic deformation (SPD) technique was studied. In this work, one of the SPD techniques, equal channel angular pressing (ECAP) was adopted as a processing tool. ECAP was carried out in route BC and processing was attempted at the lowest temperature. After ECAP, grain structure of the material was refined and considerable improvement in the microhardness of the alloy was perceived. Mainly, wear resistance of the alloy material was enhanced with successive ECAP passes. Coefficient of friction of the alloy material was decreased with successive ECAP passes. Wear resistance of the alloy was decreased with a rise in the applied load and the sliding speed. Both at low and high load condition, abrasive wear was noticed in as-cast and homogenized specimens. Whereas in ECAPed specimens, in addition to abrasive wear, oxidation wear and adhesive wear were observed in low load and it changes to abrasive wear at high load. In the ECAPed specimens, at low load transfer of iron particles from the steel disc surface to the specimen surface was identified. Â© 2020, Springer Nature Singapore Pte Ltd.
Flow Properties of Cast Al-Zn-Mg Alloys Subjected to Equal Channel Angular Pressing
(Institute of Physics Publishing helen.craven@iop.org, 2018) Manjunath, G.K.; Preetham Kumar, G.V.; Udaya Bhat, K.
Flow stress can be described as the stress necessary to continue deformation at any stage of plastic strain. The strength coefficient (K) and strain-hardening exponent (n) are the two important flow properties of the material. In the present work, flow properties of three different cast Al-Zn-Mg alloys processed by equal channel angular pressing (ECAP) were investigated. ECAP processing was carried out in a die having Î¦ = 120Â° and Î¨ = 30Â°. After ECAP processing, significant grain refinement and increase in the hardness was observed. Compression test was used to determine the flow properties of ECAP processed samples. Force-stroke data was recorded from the compression test. Flow curves were drawn by using force-stroke data. Strength coefficient and strain-hardening exponent were determined from the log-log plot of true stress-strain curves. Significant increase in the strength coefficient was observed after ECAP processing. Also, the strength coefficient is increased when the zinc content is increased in the alloy. Strain-hardening exponent was decreased with increase in the number of ECAP passes. Â© Published under licence by IOP Publishing Ltd.
Influence of Multi-directional Room-Temperature Forging Process on Microstructure and Mechanical Behaviour of Eutectic Al-12Si Alloy
(Springer, 2022) Kumara, B.; Preetham Kumar, G.V.
In the present work, the influence of multi-directional forging on the microstructure and mechanical behaviour of eutectic Al-12Si alloy at ambient temperature has been examined. The sample for multi-directional forging was prepared by melting and pouring the commercially available LM-6 aluminum alloy ingot into a casting die. Prior to the forging process, the samples were solutionized for 3Â h at 525 Â°C and then cooled in water. Light optical microscopy and scanning electron microscopy were used to examine the microstructure of materials. Microstructural observations have shown that effectively broken coarse needle-shaped plates like silicon particles with an average size of 11.7Â Âµm in length of as-cast samples into fine particles with an average size of 2.8Â Âµm in length after three cycles of forging (9 passes) and are evenly distributed in the Î±-Al phase. After three cycles, the tensile strength of the as-cast sample is enhanced from 192 to 382Â MPa, and its hardness is enhanced from 66.6 to 100.2Â Hv, respectively. X-ray diffraction analysis of Al-12Si alloys revealed the existence of Î±-Al and eutectic silicon (Si) phases. The peak broadening is also noted in X-ray diffraction pattern of three cycles, samples with cumulative strains of 2.43, which confirms the reduction in silicon particle size and grain size. Facets and tearing ridges are observed on the tensile fracture surface of forged samples. The improvement in the mechanical properties of forged samples can be attributed to the evenly distributed silicon particles and the work hardening of the aluminum phase. Â© 2022, ASM International.
Influence of Multi-directional Room-Temperature Forging Process on Microstructure and Mechanical Behaviour of Eutectic Al-12Si Alloy
(Springer, 2022) Kumara, B.; Preetham Kumar, G.V.
In the present work, the influence of multi-directional forging on the microstructure and mechanical behaviour of eutectic Al-12Si alloy at ambient temperature has been examined. The sample for multi-directional forging was prepared by melting and pouring the commercially available LM-6 aluminum alloy ingot into a casting die. Prior to the forging process, the samples were solutionized for 3 h at 525 °C and then cooled in water. Light optical microscopy and scanning electron microscopy were used to examine the microstructure of materials. Microstructural observations have shown that effectively broken coarse needle-shaped plates like silicon particles with an average size of 11.7 µm in length of as-cast samples into fine particles with an average size of 2.8 µm in length after three cycles of forging (9 passes) and are evenly distributed in the α-Al phase. After three cycles, the tensile strength of the as-cast sample is enhanced from 192 to 382 MPa, and its hardness is enhanced from 66.6 to 100.2 Hv, respectively. X-ray diffraction analysis of Al-12Si alloys revealed the existence of α-Al and eutectic silicon (Si) phases. The peak broadening is also noted in X-ray diffraction pattern of three cycles, samples with cumulative strains of 2.43, which confirms the reduction in silicon particle size and grain size. Facets and tearing ridges are observed on the tensile fracture surface of forged samples. The improvement in the mechanical properties of forged samples can be attributed to the evenly distributed silicon particles and the work hardening of the aluminum phase. © 2022, ASM International.
Influence of sic and al2o3 particulate reinforcement on the mechanical properties of za27 metal matrix composites
(Trans Tech Publications Ltd ttp@transtec.ch, 2019) Anjan, B.N.; Preetham Kumar, G.V.
Zinc aluminum based matrix composites reinforced with SiC and Al2O3 particles have significant applications in the automobile field. Stir casting method followed by squeeze process was used for fabrication. ZA27 composites reinforced with SiC and Al2O3 particles (20-50Âµm) in various weight percentage (wt%) ranges from 0-10 in a step of 5 each was fabricated. OM, SEM and EDS analysis of microstructures obtained for matrix alloy and reinforced composites were performed in order to know the effect of varying wt% on physical and mechanical properties of composites. Squeeze casting technique shows better features such as fine microstructure as a result of low porosity and good bonding between matrix and reinforcement. Addition of reinforcements decreased the densities of matrix alloy. SiC reinforced composites showed better results as compared with Al2O3 reinforced ones. Hardness and ultimate tensile strength value of 10 wt% reinforced composites showed improved results. Â© 2019 Trans Tech Publications Ltd, Switzerland.
Investigation on Microstructure and Mechanical Properties of Solution Heat-Treated and Multi Directional Forging-Processed LM-25 Aluminium Alloy
(Springer, 2020) Kumara, B.; Preetham Kumar, G.V.
The experimental study of hypoeutectic Al-7.3Si alloy on microstructure and mechanical properties processed by MDF at room temperature was reported in this paper. A commercial LM-25 aluminium alloy ingot was melted in an electric casting furnace and poured into a preheated rectangular casting die. The samples were then solutionized for 10 h at 535 °C and quenched in water for MDF processing. Microstructure analysis of the samples was done with the help of optical microscopy and scanning electron microscopy. Microstructural observation of MDF processed up to six passes sample showed that coarse eutectic silicon particles with an average length of 16 µm are effectively broken into fine particles with an average length of 4 µm and uniformly distributed in aluminium phase. After six passes, UTS of as-cast specimen is increased from 177 to 441 MPa and microhardness is increased from 75 to 127 Hv. XRD analysis of the samples confirmed the presence of Al phase and eutectic Si phase. Therefore, modification of eutectic Si particle with Al phase refinement has been demonstrated to be a very important factor for enhancing mechanical properties of aluminium–silicon alloy. © 2020, The Indian Institute of Metals - IIM.
Microstructural characterization and mechanical properties of cast Al-15Zn-2Mg alloy subjected to severe plastic deformation
(Elsevier Ltd, 2018) Manjunath, G.K.; Udaya Bhat, K.; Preetham Kumar, G.V.
In the present work, Al-15Zn-2Mg alloy was processed by ECAP technique for grain refinement. The ECAP processing was conducted at 150 Â°C. Microstructural characterization was carried out in OM, SEM, TEM and XRD. To evaluate the mechanical properties, hardness measurement and tensile tests were conducted at room temperature. Microstructural characterization showed that, ECAP processing leads to decrease in the grain size of the alloy. Also, small amount of dislocations were also observed in the ECAP processed material. After ECAP processing, precipitates nucleation in the material was identified in the XRD analysis. The strength and the hardness values were increased after ECAP processing. After ECAP processing, microhardness of the material is increased from 173 Hv to 252 Hv and the UTS of the material is increased from 166 MPa to 362 MPa. After tensile testing, fracture surface of the cast material showed dendritic structure and the fracture surface of the ECAP processed material showed dimples. Â© 2018 Elsevier Ltd. All rights reserved.
Microstructure and Wear Performance of ECAP Processed Cast Al–Zn–Mg Alloys
(Springer, 2018) Manjunath, G.K.; Udaya Bhat, K.; Preetham Kumar, G.V.; Ramesh, M.R.
In the present investigation, wear performance of equal channel angular pressing (ECAP) processed cast Al–Zn–Mg alloys under dry sliding wear conditions was studied against a steel disc. Initially, Al–Zn–Mg alloys (with 5, 10, 15% zinc and 2% magnesium) were ECAP processed. After ECAP, grain size was reduced and enhancement in the hardness was observed. Wear resistance of the alloys increased after ECAP processing. Wear resistance of the alloys also increased when the quantity of the zinc was increased in the alloys. But, wear resistance of all three alloys decreased with increase in the load and the sliding speed. Coefficient of friction of the alloys decreased after ECAP processing. Coefficient of friction of the alloys also decreased when the quantity of the zinc was increased in the alloys. Coefficient of friction of all three alloys increased with increase in the load and the sliding speed. Irrespective of the alloy composition and applied load, worn surfaces of the cast and homogenized samples were composed of plastic deformation, scratches and micro-ploughing. On the other hand, in ECAP processed samples, morphology of the worn surfaces depended on the applied load. Abrasive wear is the main wear mechanism perceived in cast and homogenized samples at all loads. While in ECAP processed samples, the wear mechanism shifted from adhesive and oxidation wear to abrasive wear with increase in the load. Formation of oxide layers on the surface of the sample increased with increase in the ECAP passes. In ECAP processed samples, transfer of iron content from the disc to the sample surface was identified. © 2018, The Indian Institute of Metals - IIM.
Microstructure Evolution in Cast Al-Zn-Mg Alloys Processed by Equal Channel Angular Pressing
(Springer New York LLC barbara.b.bertram@gsk.com, 2018) Manjunath, G.K.; Udaya Bhat, K.; Preetham Kumar, G.V.
In the present work, microstructure development and enhancement in the microhardness of Al-Zn-Mg alloys (with 5, 10, and 15% zinc) during equal channel angular pressing (ECAP) were investigated. Dendritic morphology was observed in the cast condition of all three alloys, and precipitates were situated along the inter-dendritic regions. After homogenization, precipitates in the inter-dendritic regions were uniformly distributed in the aluminum matrix and grain boundaries were developed. After 4 passes in route BC, large reduction in the grain size was observed. X-ray diffractometry showed that MgZn2 precipitate was developed in the ECAP-processed samples. Increase in the intensity of MgZn2 peaks was observed when the quantity of zinc is increased in the material. Also, changes in the intensity of XRD peaks were observed in ECAP-processed samples due to shear deformation. After ECAP, substantial increase in the microhardness was perceived. After four passes, microhardness increased to 109, 67, and 58% from the initial condition in A1, A2, and A3 alloys, respectively. Also, improvement in the microhardness was also observed when the quantity of zinc is increased in the material. © 2017, Springer Science+Business Media, LLC, part of Springer Nature and ASM International.
Severe plastic deformation of Al-15Zn-2Mg alloy: Effect on wear properties
(Trans Tech Publications Ltd ttp@transtec.ch, 2019) Manjunath, G.K.; Bhat, K.U.; Preetham Kumar, G.V.
In the present work, Al-Zn-Mg alloy having highest zinc content was deformed by one of the severe plastic deformation (SPD) technique, equal channel angular pressing (ECAP) and effect of ECAP on the microstructure evolution and the wear properties were studied. ECAP was performed in a split die and the channels of the die are intersecting at an angle of 120Â°. ECAP was attempted at least possible temperature and the alloy was successfully ECAPed at 423 K. Below this temperature samples were failed in the first pass itself. After ECAP, significant drop in the grain size was reported. Also, ECAP leads to significant raise in the microhardness of the alloy. Predominantly, after ECAP, upsurge in the wear resistance of the alloy was noticed. To figure out the response of ECAP on the wear properties of the alloy; worn surfaces of the wear test samples were analyzed in SEM. Â© 2019 Trans Tech Publications Ltd, Switzerland.
Tensile Properties and Tensile Fracture Characteristics of Cast Al–Zn–Mg Alloys Processed by Equal Channel Angular Pressing
(Springer India sanjiv.goswami@springer.co.in, 2017) Manjunath, G.K.; Preetham Kumar, G.V.; Bhat, K.U.
In the present work, as-cast Al–5Zn–2Mg, Al–10Zn–2Mg and Al–15Zn–2Mg alloys were ECAP processed and tensile tests were carried out to determine the strength and ductility. After tensile testing, morphology of the fracture surfaces of tensile tested samples were studied. After ECAP processing, significant improvement in the yield stress and ultimate tensile strength were observed in all the three alloys. Also, yield stress and ultimate tensile strength were increased with increase in the zinc content of the material. The elongation to failure increased significantly with increase in the number of ECAP passes. SEM micrographs revealed that, the fracture surface of the cast samples of the alloys were composed of the dendritic structure, while the ECAP processed samples consisted of small size dimples. Size of the dimples were reduced with the increase in the number of ECAP passes. © 2017, The Indian Institute of Metals - IIM.
Tensile toughness characteristics of cast Al-Zn-Mg alloys processed by equal channel angular pressing
(Trans Tech Publications Ltd ttp@transtec.ch, 2020) Manjunath, G.K.; Bhat, K.U.; Preetham Kumar, G.V.
In the current study, consequence of ECAP on the toughness characteristics of the Al-Zn-Mg alloys was studied. Three set of Al-Zn-Mg alloys (5, 10 and 15% Zn and 2% Mg) were selected and ECAPed. Also, consequence of zinc on the toughness characteristics of the alloy, before and after ECAP was studied. After ECAP, grain size of the alloys decreased and significant rise in the strength and ductility of the alloys were noticed. Mainly, modulus of toughness of the alloys increased with successive ECAP passes. But, the modulus of toughness of the alloys decreased with rise in the zinc in the material. Â© 2020 Trans Tech Publications Ltd, Switzerland.
The Effect of Detonation Frequency on the Linear Reciprocating Wear Behavior of Detonation Sprayed Ni-20%Cr Coatings at Elevated Temperatures
(Springer, 2025) Prasad, R.; Purushotham, N.; Preetham Kumar, G.V.; Babu, P.S.; Govindarajan, G.; Rajasekaran, B.
The study explores the impact of detonation frequency (3 and 6 Hz) on the temperature-dependent linear reciprocating wear behavior of Ni-20%Cr coatings deposited by detonation spraying on a nickel-based superalloy (IN718). Dry sliding experiments were carried out at both ambient (25 °C) and high (420 °C) temperatures, using an alumina (Al2O3) ball as the counter material and different loads (5, 10, and 20 N). HV0.2 microhardness indentations were used to test material hardness variations attributed to heat exposure. X-ray diffraction (XRD), Raman spectroscopy, and field emission scanning electron microscopy with energy-dispersive spectroscopy (FESEM with EDS) were used to investigate the wear characteristics and mechanisms. Furthermore, surface roughness and profiles of worn surfaces (including track depth, breadth, and wear volume) enabled the calculation of wear rates using confocal optical 3D profilometry. The results showed the 6 Hz Ni-20%Cr coating showed better wear resistance than the 3 Hz coating. However, a higher wear rate and low friction coefficient at 420 °C were observed due to partial oxide particles, which were insufficient to restrict direct ball-to-metal contact. The research delves into wear maps, tribolayer formation, wear mechanisms, and sub-mechanisms. © ASM International 2024.