Dominant Wear Mechanism Research Articles

Evaluation of microstructural, tribological and tensile characteristics of AA7075 surface composites fabricated through friction stir process

Superior wear resistance and a high level of tensile strength in piston ring materials are achieved using AA7075 surface composites (SCs) that are fabricated by reinforcing the steel slag (SS) particulates through proper selection of friction stir process (FSP) parameters using the multipass technique. The optical structure elucidates that fine and equi-axed grains are ascertained in the stir zone of the processed region, and by increasing the number of passes from one to three, a homogenous dispersion of particulates and a reduced grain size (9 µm) is obtained. In particular, a clear and defect-free interface is prominent on the resulting composite surface. Field emission – scanning electron microscopy (FESEM) identifies the dispersion of reinforcements, while X-ray diffraction (XRD) technique and energy dispersive spectroscopy (EDS) mapping confirm the existence of reinforcing elements. The Orowan strengthening effect and reduced oxygen content around the SiO2 and CaO elements in the three-pass FSP SC specimen tend to increase its load-bearing capacity and result in superior hardness (353.3 VHN) and tensile strength (792.6 MPa). However, the same specimen exhibits a reduced percentage (%) elongation due to multiplied fragmentation of reinforcements, which eventually restricts the plastic movement of the AA7075 matrix. The SEM fracture morphology indicates that failure occurred through a combination of ductile and brittle modes. Furthermore, the SC specimen with two passes prominently decreases the wear rate (333 × 104 mm3/m), which can be attributed to the commendable trilayer formation, and the worn morphology indicates the abrasive wear was the dominant wear mechanism. This fabricated specimen with high-strength characteristics can be beneficial for design engineers. During piston ring design, an increased level of the factor of safety can be achieved.

A Study on Outstanding High‐Temperature Wear Resistance of High‐Entropy Alloys

Wear property is a main reason for failure, especially for those parts which are mechanically moving and interacting with each other in industrial utilization. High‐entropy alloys (HEAs) are considered promising candidates to possess outstanding tribological factors of performance at high temperatures compared with conventional engineering alloys, which have drawn much attention from academic and industrial points of view. This study is performed to survey the influence of microstructure, grain size, precipitation, reinforcement, and elements addition on the wear resistance of HEAs over a wide temperature range. In this respect, the worn microstructure, wear rate, friction coefficient, hardness, wear track, and subsurface are precisely checked. This review also explores the high‐temperature wear resistance of thermally sprayed and additively manufactured HEAs associated with emphasizing the dominant wear mechanisms through in a wide range of temperatures.

High-temperature oxidation and tribological behaviors of WTaVCr alloy coating prepared by double glow plasma surface alloying technology

Tungsten-based refractory high entropy alloys (RHEAs) are a potential candidate for plasma-facing materials (PFM) due to their excellent properties. However, the oxidation resistance of W-based RHEAs is poor. Moreover, there is still a lack of research on the evaluation of room temperature wear. In this work, several WTaVCr alloy coatings were fabricated by double glow plasma surface alloying (DGPSA) technology at different temperatures and different source ratios. The microstructure of WTaVCr coatings exhibited BCC solid solution phase. The coatings were compact and uniform. The scratch test indicates that the coating combines the substrate well. The surface hardness of the samples increases significantly after alloying, which is 5 times that of the substrate. Sliding wear tests were performed on the coating as well as the substrate. The fairly low specific wear rate of the coating (W31.7Ta13.3V42.9Cr12.2) proved its excellent wear-resisting property (The wear rate was 8 × 10−7 mm3/N∙m, which was two orders of magnitude lower than that of the substrate), and the dominant wear mechanism was abrasive wear and oxidative wear. The coating (W45Ta45.4V4.5Cr5.1) showed a favorable oxidation resistance, and a continuous Cr2O3 protective layer was formed on the surface. The oxidation resistance of the coating was approximately a quarter of the W-substrate.

Dry sliding tribological properties of Cu-WS2 self-lubricating composites at 25–500 °C

Cu-WS2 composites are being used as self-lubricating materials for various engineering applications. The poor wettability between Cu and WS2 is a main obstacle for obtaining high-performance Cu-WS2. In order to improve the wettability, a thin Cu layer was deposited on the surface of the WS2 powder through an electroless plating technology. Cu-WS2 composites were prepared via spark plasma sintering (SPS) using the mix powders of Cu and Cu-WS2. Microstructure, mechanical properties and tribological properties of the Cu-WS2 composites were investigated, and that of the Cu were also comparatively studied. Results show that the WS2 powder coated with Cu (abbreviated as WS2@Cu powder) improves the poor wettability between Cu and WS2 and meanwhile the distribution of WS2. Cu-WS2 composites sintered below 750 °C could reduce the reaction between Cu and WS2 and ensure more WS2 in the composites. Both the coefficient of friction (COF) and the wear rate of the Cu-WS2 are lower than that of the Cu. A lubricant film leads to the excellent tribological properties as the Cu-WS2 composites were tested at 25−200 °C. However, the disappearance of WS2 and the formation of Cu2O cause to the decreasing self-lubricating performances at 300−500 °C. With an increase in the test temperature, the dominant wear mechanisms of the Cu-WS2 composites change from adhesive wear to a mixture of abrasive and oxidation wear, and that of the Cu change from adhesive wear to a mixture of fatigue and oxidation wear.

A new prediction model for disc cutter wear based on Cerchar Abrasivity Index

The wear evolution indicated that abrasive wear is the dominant wear mechanism for disc cutter wear. Considering the uneven rolling force distribution on the cutterhead, the relative installation radius is introduced to reflect the influence of installation radius on the rolling force, and the CSM rolling force model is corrected based on linear assumption. To accurately predict disc cutter wear, the relative sliding distance between disc cutters and rock is derived based on corrected rolling force and contact theory. The effect of installation radius, cutters radius and penetration on the relative sliding distance is investigated, the results illustrated that the relative sliding distance increase with the installation radius and penetration, conversely, the relative sliding distance increase with the disc cutter radius decrease. In addition, the relationship between wear coefficient and Cerchar Abrasivity Index (CAI) is analyzed by a series CAI test. According to CAI change trend as stylus sliding distance, the effect of stylus shear failure on the abrasivity property within initial test stage was excluded. Furthermore, A new model is proposed to predict disc cutter wear based on the relative sliding distance and wear coefficient. And the effect of installation radius, cutters radius, Uniaxial Compressive Strength (UCS), CAI et al. on the disc cutter wear is investigated, the results illustrate that the disc cutter wear increase with installation radius, penetration, UCS, CAI and spacing between adjacent cutter, conversely, the disc cutter wear increase with the cutter radius and thickness decrease. Finally, the accuracy of proposed model is verified by Yintao water conveyance tunnel project. The research of parameters provides a theoretical basis for optimizing excavation parameters and reducing cutters wear.

Microstructural evolution of worn surface and subsurface of high Mn additive iron-based hardfacings subjected to repetitive impacts and sliding

In this article, a new impact-sliding wear test setup was developed to investigate the impact-sliding tribological/wear behavior of manganese (Mn) additive iron-based hardfacings. The effect of increased Mn content from 0 to 13 wt% on the wear characteristics was examined for a constant load of 200 N, 1000 impacts and 50 strokes/min speed. Hardness evaluation tests revealed that the hardness was increased after the impact-sliding wear tests. The worn surfaces of hardfacings/alloys/hardfacing alloys containing 0 and 8 wt% Mn presented a similar mechanism of micro-abrasion, but the damage caused by the abrasion in 8 wt% Mn additive hardfacings was not so effective in comparison to the hardfacing containing 0 wt% Mn. Above 8 wt% Mn addition, oxidative wear became the dominant wear mechanism with the formation of protective tribo-oxide layers and the wear trend exhibited enhancement in the wear resistance of hardfacings. On the other hand, subsurface analysis showed severe damage under the tribo-oxide layer, which revealed that the wear trend is not an exact indicator of wear resistance of the material. Wear behavior of the hardfacings has been successfully correlated with the hardness, morphology of the worn surfaces and subsurfaces.

Aging and wear characteristics of A356 alloy with Er and Zr addition

The present work investigates the effect of aging on the microstructure, mechanical properties, and wear behaviour of the cast A356 alloy with Er and Zr addition. The aged A356-0.25Zr and A356-0.25Er alloys revealed some but not all of the eutectic and columnar structures. The microstructure of A356, A356-0.5Er, and A356-0.5Er-0.25Zr alloys exhibited large α-Al grains with discrete eutectic silicon. Various intermetallic types and morphologies were observed after the peak aging. The highest hardness (∼120 HV) and the highest tensile strength (∼215 MPa) were achieved in the A356-0.25Zr alloy under peak-aged conditions. The A356 alloy revealed the lowest weight loss and friction coefficient, though it had the least hardness. Delamination was the dominant wear mechanism in all alloys.

Elevated Temperature Wear Behavior of AZ91 Magnesium Alloy After Micro-Arc Oxidation in Single and Dual Phase Electrolytes

Abstract Low wear resistance of AZ91 alloy is the main factor limiting its more common use in industrial applications. Therefore, the micro-arc oxidation (MAO) process is mostly applied to the alloy to improve its wear resistance at room temperature (RT). However, the effect of the MAO coating on the wear behavior at elevated temperatures was investigated in limited works. In this study, the MAO process was performed on an AZ91 alloy in single-phase (silicate-containing) and dual-phase (aluminate + phosphate containing) electrolytes, and its wear behavior was investigated at both RT and 200 °C compared to the bare alloy. The results showed that the wear resistance of the alloy could be significantly improved both at RT and 200 °C, and the silicate-based electrolyte provided a better wear resistance at both temperatures. The results also showed that the dominant wear mechanism was oxidation for the bare alloy, and brittle fracture for the MAO-treated alloys.

Machining performance and wear behaviour of polycrystalline diamond and coated carbide tools during milling of titanium alloy Ti-54M

Polycrystalline diamond (PCD) is currently under development as a new generation of cutting tool material for titanium alloy machining applications. The unrivaled high temperature hardness possessed by PCD offers the potential for higher levels of productivity compared to tungsten carbide, the current industry standard tool material, through facilitating higher cutting speeds. This study investigates the performance of various PCD tool grades during square shoulder milling of Ti-54M. The influence of PCD grain size on dominant wear mechanism has been established, revealing that a smaller, sub 1 μm, grain size offers improvements in tool life due to superior fracture toughness compared to larger grained material. For fine grained PCD, loss of tool material through a cyclic process of workpiece adhesion followed by grain pull-out was identified to be the predominant wear mechanism, contrasting the mechanical fracture dominated wear observed for the larger grained PCD grades. The influence of insert microgeometry was also investigated through honing of the cutting edge radii. An increased tendency for edge fracture was demonstrated when machining with larger radii tooling which was attributed to increased cutting forces. Finally, the study has compared the surface integrity response of the workpiece following PCD and carbide machining, revealing considerably lower levels of microstructural damage and cutting forces when machining with PCD. This highlights the potential benefits of PCD in finishing applications, whereby high speed machining can be employed to reduce the impact on component surface integrity.

Influences of alloying elements on microstructure and tribological properties of a medium-weight high-entropy alloy

In this work, individual influences of Al, Fe and Ni on the microstructure, wear resistance and mechanical properties of high-entropy alloys (AlxCrFeyNizTi0.2) were studied. Microstructures and phase constituents of the alloys with different values of x, y and z were characterized via Scanning Electron Microscope, Energy Disperse Spectroscopy, and X-ray diffraction. Mechanical properties and wear resistances of the alloys were evaluated, including hardness, micro-hardness, and resistance to abrasive wear. It was shown that with increasing Al content, the FCC phase was replaced by disordered BCC (A2) and ordered BCC (B2) phases, leading to an increase in micro-hardness by ∼73% and a decrease in wear volume loss by ∼78%. Fe also increased the fraction of A2 phase, but reduced hardness by ∼41% and led to a considerable decrease in wear resistance. In contrast, Ni helped form a FCC phase, resulting in a decrease in hardness by ∼35%, and an increase in wear volume loss by ∼73%. Abrasive wear appeared to be the dominant wear mechanism, while the formed oxide scale played a role in improving the wear resistance. Efforts were made to correlate the changes in hardness and wear resistance with changes in microstructure. Among all specimens, AlCrFeNiTi0.2 and Al0.5CrNiTi0.2 reached the highest wear resistance. The results obtained help shed light on the development of advanced wear-resistant high-entropy alloys via the favorable addition of Al.

Deformation behavior of plasma sprayed Fe-based amorphous/ nanocrystalline coating under multi-scale tribological contact

Deformation behavior of Fe-based amorphous/ nanocrystalline coating synthesized by plasma spraying has been studied under multi-scale tribological contact. Nano- and micro-scale scratch investigation under constant and ramped loading revealed that deformation occurred mainly through plowing of coating surface by the probe. During low load (nano-scale) scratch tests, shear band generation was detected in the form of serrations in lateral force/ coefficient of friction curves under both constant (2 and 5 mN) and ramped (0–5 mN) loading conditions. Prominent shear bands around the scratch track with lesser fracture/ chipping were observed at high load (micro-scale) under ramped loading. Further, high load nanoscratch test under constant loading revealed aggravated fracture and chipping on the coating surface. Macro-scale deformation behavior studied using ball-on-disc dry sliding wear test at constant applied load (10 N) revealed that dominating wear mechanism in the coating was fatigue accompanied by abrasive and oxidative wear.

The chromization on hot-rolled Fe40Mn20Cr20Ni20 high-entropy alloys by pack cementation

As a surface modification technique, chromization is often used in steels to improve their wear, corrosion, and oxidation resistances. High-entropy alloys (HEAs) with excellent properties can be applied in extreme environments, perhaps to further improve their resistance to external environments by chromization. In this work, the chromization of hot-rolled Fe40Mn20Cr20Ni20 HEA was carried out by pack cementation. A chromized coating of 120 µm with the body-centered cubic (BCC) structure and a diffusion layer of 30 µm were obtained by chromizing at 1473 K for 12 h. Based on the growth kinetics of the coating, the relationship between the thickness of the chromized coating and chromized temperature as well as the time was modeled to visualize. After chromization, due to the higher chromium content of the coating, the Vickers hardness of was increased from 150 HV0.1 of hot-rolled HEA to more than 500 HV0.1, the wear rate was significantly reduced, and the dominant wear mechanisms for both hot-rolled and chromized HEAs under three test environments involved abrasion and adhesive wears. Besides, the corrosion resistance was promoted in NaCl solution (3.5 wt%). Thereby, the present work provides guidances for chromization on HEAs.

Wear Development in Oscillating Rolling Element Bearings

Rotor blade bearings enable rotor blades to pivot about their longitudinal axis and thus control the power output and reduce the loads acting on the wind turbine. Over a design period of 20 years, rolling bearings are exposed to frequent oscillation movements with amplitude ratios of x/2b > 1, especially due to new control concepts such as Individual Pitch Control, which can lead to wear and a reduction in service life. The objective of this paper was to identify the dominant wear mechanisms and their consequences for the operation of oscillating bearings. Oscillating experiments with an increasing number of cycles on the angular contact ball bearings of two different sizes (types 7208 and 7220) show that the damage initiation starts with adhesive and corrosive wear mechanisms, which result in a sharp increase in the torque as well as the wear volume on the bearing raceway. As the number of cycles increases, an abrasive mechanism occurs, resulting in a lower slope of the wear curve and a smoothing of the resulting wear depressions. The wear and torque curves were evaluated and classified using an energy-wear approach according to Fouvry.

High‐Stress Abrasive Wear Analysis of in Situ TiC‐Reinforced Zinc–Aluminum Composites Using Integrated Taguchi–TOPSIS Method

This study involves the preparation of in situ TiC‐reinforced zinc–aluminum alloy (ZA‐37) composites and analysis of their high‐stress abrasive wear behavior. The wear rate, friction coefficient, and frictional heating of the composites are investigated using a pin‐on‐disk wear tester. The experiments are carried out based on a plan created using Taguchi's technique. TOPSIS methodologies are used to determine the effects of applied load, abrasion distances, TiC contents on wear rate, coefficient of friction, and frictional heating throughout the wearing process. The results reveal that the composite with 10 wt% TiC exhibits the highest level of wear resistance among all samples. It is found that ploughing, microcutting, and delamination were the dominant wear mechanisms in general. However, in the optimum combination, mild abrasion and microploughing prevail. As per TOPSIS analysis, the reinforcement content affects the wear rate of test materials the most followed by applied load and abrading distance. Under the optimal combination of parameters, the in situ TiC composite has the potential of replacing the conventional gray cast iron utilized in bearing applications.

Synergetic influence of TiCnp and graphite particles on tribological performance of Cu based composites prepared by flake powder metallurgy

The Cu base composites play a key role in multiple industrial applications such as bearing materials and carbon brushes owing to their superior thermal, mechanical and tribological features. Therefore, in the present investigation, synergetic influence of nano titanium carbide (TiCnp) and graphite particles (Grp) on tribological behaviour of Cu base self-lubricating composites have been studied. The composites with fixed 5wt% of Grp and varying amounts (1.5wt% to 4.5wt%) of TiCnp were prepared via flake powder metallurgy (flake PM) technique. The sintered samples were characterized by different techniques for phases, physical, morphological and mechanical properties. Pin-on-disc (POD) tribotester has been used to analyse the tribological behaviour of composites in dry sliding condition by varying loads (10 N to 30 N) and sliding velocities (0.75 m/s and 1.5 m/s) for a fixed sliding distance of 2000 m. The results indicate the successful formation of Cu-Grp and TiCnp-reinforced Cu-Grp composites. With addition of Grp, the wear rate and coefficient of friction (COF) of Cu matrix is reduced. The wear rate is further reduced with the incorporation of TiCnp particles. But, the COF shows the enhancement. The composite having 5wt% Grp–4.5wt% TiCnp shows the minimum wear and maximum hardness. The energy-dispersive spectroscopy (EDS) elemental mapping of worn surfaces indicates that TiCnp mechanically interlocks the graphite at the interface and prevent its removal and reduces the wear rate. The worn surface investigation also shows that the dominant mechanism of wear for pure Cu sample is delamination in nature. However, the mechanism of wear for TiCnp-reinforced composites is a combination of abrasive and delamination wear.

Effects of normal load and reciprocating frequency on the tribological behaviors of a Zr-based bulk metallic glass

Bulk metallic glasses (BMGs) are a class of novel engineering materials of high hardness, high strength, and excellent fracture toughness which imply prospective outstanding wear resistance. However, for the non-intrinsic character of tribological properties, the wear behaviors and mechanisms of BMGs remain to be clarified. In this work, linear reciprocating tribological behaviors of a Zr60.14Cu22.31Al9.7Fe4.8Ag3 (at.%) BMG against GCr15 steel balls were characterized in the “ball-on-plate” mode under normal loads of 1–15 N and at reciprocating frequencies of 1–12 Hz with a stroke length of 5 mm. The results indicate that high coefficient of friction (COF) was observed under low normal load plus high reciprocating frequency, whereas low COF was observed under high normal loads or at low reciprocating frequencies, and that the specific wear rate increased with both normal load and reciprocating frequency wherein the reciprocating frequency played a more crucial role. Via systematic examinations on the worn surfaces of both BMG plates and GCr15 steel balls and on the wear debris, transition of the dominating wear mechanisms from oxidative wear and abrasive wear to adhesive wear with increasing normal load and reciprocating frequency was detected and the role played by plastic deformation of BMG in the process was tentatively illustrated. The current work would help to understand the tribological properties of Zr-based BMGs under sliding conditions.

Abrasive Wear Behavior of Al–4Cu–1.5Mg–WC Composites Synthesized through Powder Metallurgy

Different Al–4Cu–1.5Mg/WC composites were synthesized through powder metallurgy to establish the effect of WC particle addition on the abrasive wear behavior of an Al–4Cu–1.5Mg (wt. %) alloy. The wear tests were performed using a pin-on-disc tribometer at room temperature in dry conditions using SiC abrasive sandpaper as a counterbody and tribometer of linear configuration. The results showed that WC additions increase the hardness of the Al–4Cu–1.5Mg alloy due to the strengthening effect of particle dispersion in the aluminum matrix, which generates an improvement in the wear resistance of the composites by preventing direct contact of the sample with the counterbody, in turn delaying the plastic deformation phenomena responsible for the degradation sequence. In addition, the dominant wear mechanism was abrasive wear, and the increased friction coefficient did not bring a rapid wear rate, which was related to the enhanced deformation resistance due to the high hardness.

Comparison of tribocorrosion resistance of Inconel® 718 alloy manufactured by conventional method and laser powder bed fusion method

Additive manufacturing is a technology increasingly used in industry because of its ability to produce parts with complex shapes. The main objective of the research was to determine wear due to friction and corrosion (tribocorrosion) and to determine the dominant wear mechanism at different ball loads for Inconel 718 manufactured by laser powder bed fusion and cast process. Additively manufactured IN718 produced by LPBF method shows higher resistance to both tribocorrosion at 3.5% NaCl and only mechanical wear than material produced by casting. For both tested variants of IN718 material, tribocorrosion wear was significantly higher than purely mechanical wear. The test results provide a guide for the design of IN718 components that may be subject to wear due to friction and corrosion.

Microstructures and elevated temperature mechanical properties of AlSi12Cu4Ni2 fabricated by laser powder bed fusion

The key properties of cast AlSi12Cu4Ni2 alloy are elevated temperature performance. In this paper, the microstructures and mechanical properties of a multiphase AlSi12Cu4Ni2 alloy formed by laser powder bed fusion (LPBF) were investigated from ambient temperature to 350 °C. The effects of LPBF parameters and microstructure in AlSi12Cu4Ni2 samples on mechanical properties were systematically studied. The best operating conditions (P = 300 W, v = 1800 mm/s) are obtained. The results show that fine equiaxed grains can be obtained by LPBF forming. The strengthening mechanisms were revealed. The thermal stability of the Al7Cu4Ni and Al3CuNi phases are conducive to the excellent elevated-temperature tensile strength. The high temperature wear properties of AlSi12Cu4Ni2 alloy were investigated. Abrasive wear is dominant wear mechanism of AlSi12Cu4Ni2 alloy at high temperatures.

Highly wear resistant dual-phase (Ti-Zr-Nb-Hf-Ta)C/(Ti-Zr-Nb-Hf-Ta) B2 high-entropy ceramics

ABSTRACT Wear characteristics of a fine-grained dual-phase high-entropy (Ti0.14Zr0.2Nb0.2Hf0.2Ta0.26)C + (Ti0.38Zr0.18Nb0.22Hf0.115Ta0.105)B2 were investigated using the ball-on-flat technique/dry sliding in air. The experimental material showed very high density with a value of 8.72 g/cm3 and a small grain size of HEC and HEB grains with values of 0.95 ± 0.30 and 0.99 ± 0.27 μm, respectively. The nano-hardness of the HEC and HEB grains is very high with mean values of 37.4 ± 2.3 and 43.0 ± 2.9 GPa, respectively with the micro-hardness of the dual system HV1 29.4 ± 2.0 GPa. The friction coefficient values during the test with 5 and 10 N increased from a value of 0.4 and reached the values 0.65 and 0.77 at the sliding distances of approximately 1500 and 1000 m, respectively. The specific wear rate decreased with increasing sliding distance at 5 N load, from 4.75 × 10−7 mm3/Nm to 4.2 × 10−7 mm3/Nm and at 10 N from 2.1 × 10−7 to 1.7 × 10−7 mm3/Nm. The dominant wear mechanisms in both cases were an oxidation-driven tribo-chemical reaction and tribo-layer formation in boride grains and mechanical wear in carbide grains.