Characteristics of Extrusive Wear and Transition of Wear Mechanisms in Elevated-Temperature Wear of a Carbon Steel

The dry sliding wear of a medium carbon steel with different microstructures was measured under the normal load range of 50–150 N at 400°C by a pin-on-disc high-temperature wear setup. The wear behavior and wear mechanism were systematically studied; in particular, the characteristics of extrusive wear and the transition of wear mechanisms were investigated. Under low normal loads, the wear is oxidative type wear. Once the normal load reached a critical value, a mild-to-severe wear transition occurred, and subsequently an extrusive wear prevailed. The mild-to-severe wear transition depended on the microstructure of matrix; the critical normal load of the transition was 112.5 N for tempered sorbite, 125 N for lamellar pearlite, and 137.5 N for tempered martensite and tempered troostite. As oxidative wear prevailed, a thick oxide layer about 20–30 μ m and a plate-like wear debris with regular outline were recognized. However, as the extrusive wear occurred, the wear rate abruptly increased but the friction coefficient was reduced. The extrusive wear predominated due to thermal softening of the matrix and presented a superthin oxide layer (less than 0.5 μ m) and low oxide content on worn surfaces, accompanied by the appearance of ribbon-like wear debris.     

Tribological behaviour of DLC coatings compared to different materials used in hip joint prostheses

The goal of the study carried out in the laboratory was to quantify the wear and the friction of two materials used for the manufacturing of hip prostheses. Tests used had to obtain in a short time the tribological behaviour laws of the materials. Tests on a hip simulator have been excluded because their cost and their duration were too high for a program of preliminary development of new materials.

To amplify wear phenomena, dry friction tests were carried out for two configurations: ball-on-disc and pin-on-disc. The influence of the contact pressure at constant sliding velocity on the wear of materials has been clearly shown.

Results obtained with several different tested materials (stainless steel/UHMWPE, stainless steel+DLC coating/UHMWPE, stainless steel+DLC coating/stainless steel+DLC coating, titanium alloy+DLC coating/UHMWPE, titanium alloy+DLC coating/titanium alloy+DLC coating, zirconium dioxide/UHMWPE, alumina/UHMWPE, alumina/alumina) have shown the superiority of DLC coatings. Promising results obtained during this study are in the validation stage on a hip simulator.     

Wear Behavior of Magnesium Alloy AZ91 Hybrid Composite Materials

The influence of hybrid reinforcements including silicon carbide and graphite particles with a size 37–50 μm on the wear characteristics of AZ91 magnesium alloy was studied. The dry sliding wear test was conducted using a pin-on-disc wear testing machine in the load range of 20 to 80 N at different sliding velocities in the range of 1.047 to 2.618 m/s. The results show that the wear resistance of composites was much better than that of the base matrix material under the test conditions. At a speed of 1.047 m/s and load of 40 N, the wear rate (mm³/km) of the unreinforced alloy was 6.3, which reduced to 3.8 in the case of 3% reinforced composite. The antiwear ability of magnesium alloy composite was found to improve substantially with the increase in silicon carbide and graphite content from 1 to 3% by weight and the wear rate was found to decrease considerably. At a speed of 1.047 m/s and load of 80 N, the wear rate (mm³/km) reduced from 11.8 to 9.1 when the reinforcement content increased from 1 to 3%. However in both the unreinforced alloy and reinforced composite, the wear rate increased with the increase in load and sliding velocity. An increase in the applied load increases the wear severity by changing the wear mechanism from abrasion to particle cracking-induced delamination. The worn surface morphologies of the composite containing 3% reinforcement by weight for the sliding velocity of 1.047 m/s were examined using scanning electron microscopy. Different wear mechanisms, namely, abrasion, oxidation, and delamination, have been observed.     

Effect of Normal Load and Sliding Distance on the Wear Behavior of NiTi Alloy

Effect of normal load and sliding distance on the room temperature dry sliding wear behavior of a Ti-50.3 at% Ni alloy against a bearing steel was studied. The wear tests were conducted using a pin-on-disk tribometer under normal loads of 20, 40, 50, 60 and 80 N for sliding distances up to 1000 m. The wear results showed that the wear rate of NiTi alloy decreased as the normal load increased from 40 N to 60 N. Formation of iron rich tribological oxide layers under the higher loads could be the main reason of decrease in the wear of NiTi alloy. Increasing the sliding distance decreased the wear rate of NiTi alloy under normal loads of 60 N and 80 N, which was attributed to the formation of more stable iron rich tribological oxide layers on the worn surfaces of NiTi alloy.     

Dry Sliding Wear Behavior and a Proposed Criterion for Mild to Severe Wear Transition of Mg–3Al–0.4Si–0.1Zn Alloy

Wear behavior of Mg–3Al–0.4Si–0.1Zn alloy was studied as a function of applied load and sliding speed under dry sliding conditions using a pin-on-disk configuration within 20–380 N and 0.1–4.0 m/s. An empirical wear transition map has been constructed to delineate the conditions under which severe wear initiated. The roles of microstructural evolution, hardness change in subsurface and surface oxidation on wear transition were also studied. The results indicate that the transition to severe wear occurs when the deformed microstructure in surface layer of material transforms into dynamic recrystallization (DRX) microstructure. A contact surface DRX temperature criterion for mild to severe wear transition is proposed, and the contact surface DRX temperatures are calculated using activation energy obtained by hot compression tests. A model for predicating mild to severe wear transition load has been developed based on the proposed contact surface DRX temperature criterion. The mild to severe wear transition loads are well predicted within the sliding speed range of 0.8–4.0 m/s.     

Tribological Behavior of Ti3Al2.5V Alloy Sliding against EN-31 Steel under Dry Condition

This article aims to study the friction and wear behavior of Ti3Al2.5V alloy sliding against EN-31 steel under dry condition using a multi-tribotester. The effect of variation in load and sliding velocity on wear rate, average coefficient of friction, and contact temperature has been studied and analysis of wear debris has been carried out. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were employed to study the morphology of the wear tracks and deduce microchemical information at the elemental level of worn samples, respectively. Results reveal that the wear rate of Ti-3Al-2.5V increases with increasing sliding velocity and increasing normal load with few exceptions. The average coefficient of friction decreases as the normal load increases with exceptions at some loads. SEM micrographs of worn samples obtained at different loads and sliding velocities show the formation of wear tracks on the surface due to ploughing and flaking of the matrix. The main mechanism responsible for wear of Ti3Al2.5V alloy sample is rupture of the matrix and abrasion. Wear debris analysis shows irregular-shaped wear particles with very sharp edges that appeared to be plastically deformed at high sliding velocity, whereas the wear debris is very loose and fine at lowest sliding velocity.     

Microstructure and tribological properties of Al-Pb alloy modified by high current pulsed electron beam

In the present work, Al-Pb alloy was irradiated by high current pulsed electron beam. X-ray diffractometer, electronic probe microanalysis, scanning electron microscopy and Knoop hardness indentation were used to characterize the microstructure and mechanical property of Al-Pb alloy. The results show that the microstructure and mechanical property can be greatly improved. The tribological properties of high current pulsed electron beam irradiated Al-Pb alloy were investigated under dry sliding conditions using a pin-on-disc type wear testing machine. The overlapped zone beneath the melted zone exhibits good resistance to wear. Optical observation and scanning electron microscopy analysis reveal that the low wear rate and lowest level in coefficient of friction at high load level for irradiated Al-Pb alloy are due to a lubricious tribolayer covering almost the entire worn surface. The wear mode varies from oxidative wear at low load to film spalling at high load and, finally, adhesive wear.     

Dry reciprocating wear of Al-Si-SiCp composites: A statistical analysis

In this paper, effect of various wear test and material related parameters (applied load, sliding distance, reciprocating velocity, counter surface temperature and weight percentage of silicon) on dry wear behavior of two Al-Si-SiC_p composites under reciprocating conditions was studied using fractional factorial design. Developed mathematical model showed that Al-Si-SiC_p with high silicon content composite is subjected to a lower wear compared to that of low silicon composite. The applied load, sliding distance, reciprocating velocity and percentage silicon weight in composite are the four important and controlling factors; counter surface temperature has a minor effect on the wear of the composite specimens in dry condition.     

Dry sliding wear of fly ash particle reinforced A356 Al composites

In the present study aluminium alloy (A356) composites containing 6 and 12 vol. % of fly ash particles have been fabricated. The dry sliding wear behaviour of unreinforced alloy and composites are studied using Pin-On-Disc machine at a load of 10, 20, 50, 65 and 80 N at a constant sliding velocity of 1 m/s. Results show that the dry sliding wear resistance of Al-fly ash composite is almost similar to that of Al₂O₃ and SiC reinforced Al-alloy. Composites exhibit better wear resistance compared to unreinforced alloy up to a load of 80 N. Fly ash particle size and its volume fraction significantly affect the wear and friction properties of composites. Microscopic examination of the worn surfaces, subsurfaces and debris has been done. At high loads (>50 N), where fly ash particles act as load bearing constituents, the wear resistance of A356 Al alloy reinforced with narrow size range (53–106 μm) fly ash particles were superior to that of the composite having the same volume fraction of particles in the wide size range (0.5–400 μm).     

The Role of Reversible Martensitic Transformation in the Wear Process of TiNi Shape Memory Alloy

It has been established that the superelastic effect of TiNi alloy is related to a reversible martensitic transformation; that is, stress-induced transformation. The high elastic recovery of TiNi alloy has made it a potential candidate for high wear resistance applications. In the present study the tribological behavior of superelastic TiNi alloy was studied and compared to Ni, Ti, and AISI 304 stainless steel using dry sliding wear and friction tests. The effect of normal load and testing temperature on superelasticity has been investigated. It has been found that although AISI 304 stainless steel and superelastic TiNi alloy have similar hardness, TiNi exhibits superior wear resistance. The wear rate of AISI 304 stainless steel is over four times higher than TiNi. The superior wear resistance of TiNi and the effect of load and temperature on wear were discussed and related to the reversible martensitic phase transformation, as well as self-accommodation and stabilization of martensite.     

Sliding wear transition for the CW614 brass alloy

Dry sliding wear tests were performed on a CW614 brass alloy using a pin-on-ring configuration. Wear kinetics were measured within a load range of 20–80 N and sliding velocity ranging from 1 to 7 m/s. Chemical compositions, morphologies and microstructures of worn surfaces and wear debris were characterised by scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDS). Two main wear regimes have been observed: severe wear and mild wear. The results of wear tests and metallographic investigations on worn surfaces have been summarised in a wear mechanism map. It was found that the wear transition is controlled by a critical temperature at the contact surface.     

Tribological behaviour of plasma nitrided Ti-5Al-2Nb-1Ta alloy against UHMWPE

A detailed study has been made on the wear behaviour of untreated and plasma nitrided Ti-5Al-2Nb-1Ta orthopaedic alloy against ultra high molecular weight polyethylene (UHMWPE) using pin on disc tribometer under lubricated conditions. The effects of nitriding temperature and nitriding time on the basis of the evolution of the wear volume loss and friction coefficient were investigated. The wear resistance of the plasma nitrided alloys increased considerably when compared to the untreated alloy. The wear debris identified using X-ray diffraction measurements indicated the formation of titanium oxide and titanium oxynitride particles. The wear rate was found to increase with increase in load and sliding velocity.     

Microstructural and sliding wear behaviour of a heat-treated zinc-based alloy

The effect of heat treatment on microstructure, hardness, tensile properties, fracture mode and wear behaviour during lubricated and dry sliding of the zinc-based alloy with 25 wt.%Al was studied. Microstructural investigation and chemical analysis of as-cast and heat-treated specimens, the fracture and worn surfaces, as well as wear debris were performed by scanning electron microscopy and energy dispersive spectroscopy. Wear tests were carried out using a disc-on block-type wear machine. By a relatively simple heat treating consisting of a short-term annealing in the single-phase region followed by water-quenching, the elongation has been markedly improved, while the strength was maintained high. The results indicate that the wear rate strongly depends on the microstructure, applied load and sliding conditions. The wear rate increases with load, and under dry sliding conditions the wear rate is approximately two orders of a magnitude higher than under lubricated conditions. During dry sliding the best wear behaviour was displayed by the water-quenched specimens, whereas slowly cooled specimens showed the higher wear rate. Lubrication strongly affects the wear behaviour. Contrary to dry sliding, slowly cooled specimens exhibit the best wear properties under lubricated conditions. The wear mechanisms were proposed for dry and lubricated sliding. An erratum to this article can be found at     

Wear Behavior of Cooling Slope Rheocast A356 Al Alloy

In the present study, the dry sliding wear behavior of rheocast A356 Al alloys, cast using a cooling slope, as well as gravity cast A356 Al alloy have been investigated at a low sliding speed of 1 ms^?1, against a hardened EN 31 disk at different loads. The wear mechanism involves microcutting–abrasion and adhesion at lower load for all of the alloys studied in the present work. On the other hand, at higher load, mainly adhesive wear along with oxide formation is observed for gravity cast A356 Al alloy and rheocast A356 Al alloy, cast using a 45° slope angle. Unlike other alloys, 60° slope rheocast A356 Al alloy is found to undergo mainly abrasive wear at higher load. Accordingly, the rheocast sample, cast using a 60° cooling slope, exhibits a remarkably lower wear rate at higher load compared to gravity cast and 45° slope rheocast samples. This is attributed to the dominance of abrasive wear at higher load in the case of rheocast A356 Al alloy cast using a 60° slope. The presence of finer and more spherical primary Al grain morphology is found to resist adhesive wear in case of 60° cooling slope processed rheocast alloy and thereby delay the transition of the wear regime from normal wear to severe wear.     

Comparative Study of Wear Behaviors of a Selected Titanium Alloy and AISI H13 Steel as a Function of Temperature and Load

A comparative study of the wear behaviors of a selected titanium alloy and AISI H13 steel as a function of temperature and load was performed on a high-temperature wear tester. The titanium alloy and H13 steel presented totally different wear behaviors with the variation in temperature and load. Their behaviors are suggested to be attributed to the protective ability of tribo-oxides and the thermal softening resistance of the matrix. Compared to H13 steel, the titanium alloy presented poor room-temperature wear resistance, excellent high-temperature wear resistance, and an extremely protective function of tribo-oxides.     

RETRACTED ARTICLE: Wear Mechanism for In Situ TiC Particle Reinforced AZ91 Magnesium Matrix Composites

TiC reinforced AZ91 magnesium matrix composites have been fabricated by a melt in situ reaction spray deposition. The microstructures of spray-deposited alloys were studied by using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The dry sliding wear behavior of the alloys was investigated by using a pin-on-disc machine under five loads, namely 10, 20, 30, 40, and 50 N. The composites had much better wear-resistance than the matrix alloy. The wear behavior of the composites was dependent on the TiC content in the microstructure and the applied load. The improvement in the wear resistance of the composites became more prominent at larger normal load. At a lower load (10 N), with increasing TiC content, the wear rate of the composite was decreased, and the dominant wear mechanism was an oxidative mechanism. At a higher loads (50 N), a spray-deposited AZ91/TiC composites exhibited superior wear resistance to the AZ91 magnesium alloy, and the dominant wear mechanism was delamination.     

Effects of sliding velocity on tribo-oxides and wear behavior of Ti–6Al–4V alloy

Dry sliding wear tests were performed for Ti–6Al–4V alloy on a pin-on-disc wear tester. The wear behavior of Ti–6Al–4V alloy at sliding velocities of 0.5–4 m/s was studied and the tribo-oxides and their function were explored. Ti–6Al–4V alloy presented a marked variation of wear rate as a function of velocity. With the rise and fall of wear rate, Ti–6Al–4V alloy underwent the transitions of wear mechanisms from the combination of delamination wear and oxidative wear at lower speeds to delamination wear at 2.68 m/s, and then to oxidative wear at 4 m/s. These phenomena were attributed to the appearance and disappearance of tribo-oxides. In spite of trace or a small amount, tribo-oxides would change the wear behavior, and even wear mechanism.     

Relations of counterface materials with stability of tribo-oxide layer and wear behavior of Ti–6.5Al–3.5Mo–1.5Zr–0.3Si alloy

Dry sliding wear tests of Ti–6.5Al–3.5Mo–1.5Zr–0.3Si alloy (TC11 alloy) sliding against AISI 52100 and AISI M2 steels were performed under the load of 50–250 N at 25–600 °C. For two kinds of counterface materials, the titanium alloy presented totally different wear behaviours as the function of temperature. The appreciable variations of the titanium alloy sliding against different counterface materials were attributed the fact that a hard counterface caused unstable existence of tribo-layers by its microcutting action, thus resulting in the increase of wear rate. It is suggested that the hard counterface must be avoided as the counterface for the titanium alloy/steel sliding system.     

Frictional hardening and softening of steel 52100 during dry sliding

The behavior of frictional hardening and softening of steel 52100 with different microstructures during dry sliding was studied based on dynamic metallographic analysis. It was demonstrated that such frictional behavior significantly affected wear resistance of the steel. The results showed that anti-softening microstructures exhibited a rather better wear resistance; the difference in the wear resistance of various steels with different microstructures was caused by the difference in the energy consumption in surface layers during wear. These results indicate that the original structures and properties of steels should not be taken as the only criterion for judging the wear resistance. It is necessary to consider the influence of dynamic microstructural changes under specific wear conditions in order to evaluate the wear resistance.     

Tribological properties of plasma sprayed and laser remelted 75/25 Cr3C2/NiCr coatings

A CO₂ laser was used to fuse based Ni–Cr Cr₃C₂ coatings for the purpose of homogenizing their microstructures and eliminating their porosity. Tests of layer control and wear resistance were carried out on the samples treated with the laser. The results have shown that laser remelting improves the microstructure of the coatings, increases the coating microhardness, and improves coating–substrate adherence. The dry sliding wear behaviour was characterized by the existence of two periods. During the first period the square of the wear volume is proportional to the sliding distance. During the second, the wear volume is proportional to the sliding distance.