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.     

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.     

Relation Between Tribolayers and Wear Behavior During Dry Sliding of Fe-Al Hot-Dipped Coating

An Fe-Al coating consisting of FeAl and Fe₃Al was prepared on AISI 1045 steel by hot-dip aluminizing and subsequent high-temperature diffusion. Dry sliding wear tests were performed for Fe-Al coating against AISI 52100 steel under various sliding speeds and loads. During sliding, thin tribolayers formed on the worn surfaces of the Fe-Al coating. After wear, they were observed to be a nonoxidized mechanically mixed layer (MML) at 0.5 m/s, an oxide-containing MML at 0.75–2.68 m/s, and an in situ oxide layer at 4 m/s. The tribolayers presented a close relation with the wear behavior. Because of their different ingredients, structures, and types, the tribolayers resulted in significant changes in the wear behavior. At 0.75–2.68 m/s (except for 2.68 m/s, 40 N), the compact tribooxide layers exerted a protective function for Fe-Al coating to reduce the wear rate. However, for the tribolayers containing no or trace tribooxides at 0.5 m/s or the unstable ones formed at 2.68 m/s, 40 N and 4 m/s, no protection was presented. In these cases, the Fe-Al coating would be partly or totally ground off, thus presenting poor wear resistance at high wear rates.     

Wear Behavior of Aluminum Alloys at Slow Sliding Speeds

The investigated slow sliding speeds presented in this work enable the understanding of the wear behavior on aluminum alloys and could possibly facilitate the completion of the previously proposed wear mechanism map for aluminum at this slow sliding speed range. Dry sliding block-on-ring wear tests were carried out on aluminum alloys, AA5754 (Al-Mg), AA6082 (Al-Mg-Si), and AA7075 (Al-Zn-Cu), at a very slow sliding speed range (<0.01 m/s). A bearing steel ring of AISI 52100 was used as the counterbody. Tests were performed at varying contact pressures, 20, 100, and 140 MPa, and sliding speeds ranging from 0.001 to 1.5 m/s. The wear tracks and debris collected were examined by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD), with the aim of analyzing their morphology and composition. At relatively slow sliding speeds (>0.01 m/s), the specimens exhibited a wear process placed at the mild wear regime, characterized by oxidation and delamination mechanisms of both the aluminum specimen and the steel ring. However, at very slow speed range (<0.01 m/s), an increase in the wear rate and the friction coefficient is observed for all of the aluminum alloys, thus suggesting that an alternative wear mechanism could be taking place.     

Effects of Aging Treatments on the High-Temperature Wear Behavior of 60Nitinol Alloy

This study was undertaken to investigate the effect of heat treatments on the high-temperature wear behavior of 60Nitinol. The samples were hot-worked, aged at two temperatures of 400 and 700°C for 1 h and then water quenched. The microstructure of the alloys was investigated by scanning electron microscopy and X-ray diffraction. Sliding wear tests were performed at two temperatures of 25 and 200°C using three types of 60Nitinol disks: hot-worked, aged at 400°C, and aged at 700°C. All wear tests were performed at a speed of 0.3 m/s under a normal load of 60 N for a total sliding distance of 1,000 m using WC-Co pins sliding against 60Nitinol disks. The worn surfaces and microstructure of the subsurfaces were studied by scanning electron microscopy. Compression and hardness tests were also performed to characterize the mechanical properties of the alloys. The highest fracture strain and lowest hardness were obtained for the sample aged at 700°C that contained Ni₃Ti₂ precipitants. This sample also showed the maximum wear resistance at a wear testing temperature of 200°C. This was attributed to the formation of a more compact and stable tribological layer on the worn surface of the softer sample.     

Friction and Wear Behavior of Steels under Different Reciprocating Sliding Conditions

The friction and wear behavior of ISO 100Cr6 steel ball sliding against conventionally hardened carbon and low-alloy steels was studied. The effect of hardness, hardening capacity, normal load, and sliding speed on the coefficient of friction and friction energy was investigated. Friction tests were carried out, without lubrication and under ambient conditions, on a reciprocating friction tester in which a ball-on-flat contact configuration was adopted. The results showed that there is a relative tendency for the friction properties to decrease with increased hardening capacity and decreased hardness. The results showed that increasing normal load decreases the coefficient of friction for the two steel nuances. However, increasing sliding speed increases the coefficient of friction of low-alloy steel and decreases the coefficient of friction of carbon steel. The oxidation of wear debris influences the wear mechanisms and friction behavior.     

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.     

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 properties of flame sprayed Fe–Ni–RE alloy coatings under reciprocating sliding

Fe–Ni–RE self-fluxing alloy powders were flame sprayed onto 1045 carbon steel. The tribological properties of Fe–Ni–RE alloy coatings under dry sliding against SAE52100 steel at ambient conditions were studied on an Optimol SRV oscillating friction and wear tester in a ball-on-disc contact configuration. Effects of load and sliding speed on tribological properties of the Fe–Ni–RE coatings were investigated. The worn surfaces of the Fe–Ni–RE alloy coatings were examined with a scanning electron microscopy(SEM) and an energy-dispersive spectroscopy(EDS). It was found that the Fe–Ni–RE alloy coatings had better wear resistance than the SAE52100 steel. An adhered oxide debris layer was formed on the worn surface in friction. Area of the friction layer varied with variety of sliding speed, but did not vary with load. The oxide layer contributed to decreased wear, but increased friction. Wear rate of the material increased with the load, but dramatically decreased at first and then slightly decreased the sliding speed. The friction coefficient of the material was 0.40-0.58, and decreased slightly with the load, but increased with sliding speed at first, and then tended to be a constant value. Wear mechanism of the coatings was oxidation wear and a large amount of counterpart material was transferred to the coatings.     

Effect of Temperature on the Dry Sliding Friction and Wear of Rice Bran Ceramics against Different Counterpart Materials

In this study, we investigated the effect of temperature on the friction and wear of rice bran (RB) ceramics, a hard porous carbon material made from rice bran, sliding against alumina, stainless steel, and bearing steel balls under dry conditions. Friction tests were performed using a ball-on-disk-type friction tester wherein a ceramic heater was installed in the rotational stage. The surface temperature of the RB ceramic disk specimens was controlled at 20, 100, 150, or 200°C. The normal load was 1.96 N, sliding velocity was 0.1 m/s, and number of cycles was 20,000. The effect of surface temperature on the friction and wear of RB ceramics substantially differed among the ball material types. The friction coefficient for the RB ceramics sliding against an alumina ball decreased with increasing temperature and exhibited an extremely low value (0.045) at 200°C. The friction coefficient in the case of the RB ceramics sliding against a stainless steel ball exhibited a stable value as the temperature was increased to 150°C and slightly decreased as the temperature was increased further, reaching a low value of 0.122 at 200°C. The friction coefficient for the RB ceramics sliding against bearing steel ball drastically increased with increasing temperature, reaching 0.381 at 200°C. The specific wear rate of the RB ceramics increased with increasing temperature; it was lowest when sliding against alumina and highest when sliding against bearing steel. The wear of the alumina ball was the lowest and that of the bearing steel ball was the highest under all investigated temperature conditions. On the basis of these results, we concluded that alumina is a promising counterpart material for RB ceramics sliding at high temperatures (≤200°C).     

Wear and Friction Characteristics of a Selected Stainless Steel

Dry sliding wear tests were performed for 3Cr13 steel with various tempered states at 25–400°C; wear and friction characteristics as well as the wear mechanism were explored. With an increase in test temperature, the wear rate decreased accompanied by an increase in tribo-oxides. The fluctuation of friction coefficient was slight at 25–200°C but became violent at 400°C. At 25–200°C, adhesive wear prevailed due to trace or less tribo-oxides; at 400°C, oxidative wear prevailed with the predominant tribo-oxides of Fe₃O₄ and Fe₂O₃. It can be suggested that the antioxidation of the stainless steel postponed the occurrence of oxidative wear to a higher test temperature. For adhesive wear, the wear resistance, roughly following Archard's rule, was directly proportional to hardness besides the specimen tempered at 500°C with grain boundary brittleness. But for elevated-temperature wear, a better wear resistance required thermal stability and an appropriate combination of hardness and toughness.     

沙尘环境对金属抗磨损特性的影响

通过向摩擦副所在隔离空间内鼓沙的方式实现对自然沙尘环境的模拟。在沙尘环境和干摩擦情况下,对比研究了随着载荷的增加,沙尘环境的存在对C52100铜、2124铝、AISI-1045钢、Z25铸铁、AISI-52100钢5种不同硬度的典型金属抗磨损行为的影响。结果表明,在沙尘条件下,5种金属的磨损率随载荷的变化呈现一定的变化规律,C52100铜和52100钢的磨损率均随载荷的增加而减小,2124铝和Z25铸铁的磨损率随载荷的增加而增大,而1045钢的磨损率则先增大后减小,但磨损率随载荷变化非常小。沙尘的存在使52100钢、1045钢和Z25铸铁的磨损率比干摩擦条件下有大幅度的减小,但是却加剧了2124铝在较高载荷下的磨损,这说明对不同的材料而言,沙尘所起的作用是不同的,它可能会加剧材料的磨损,但也有可能提高材料的抗磨损性能。     

Effect of Sintering Temperature and Atmosphere on Nonlubricated Sliding Wear of Nano-Yttria-Dispersed and Yttria-Free Duplex and Ferritic Stainless Steel Fabricated by Powder Metallurgy

The nonlubricated sliding wear behavior of nano-yttria-dispersed and yttria-free duplex and ferritic stainless steel against a diamond tip was studied. The stainless steel samples were fabricated by a conventional powder metallurgy route in which nano-yttria-dispersed and yttria-free duplex and ferritic stainless steel powders were cold compacted and then conventionally sintered at either 1000, 1200, or 1400°C in an argon atmosphere. For comparison, another set of samples was sintered at 1000°C in a nitrogen atmosphere. The wear behavior of sintered stainless steel samples against a diamond indenter was investigated using a pin-on-disc apparatus at 10 and 20 N loads and at a constant speed of 0.0041 m/s. It is proposed that yttria-dispersed stainless steels showed higher wear resistance compared to yttria-free stainless steel due to their improved hardness and density. Stainless steel sintered in a nitrogen atmosphere exhibited better wear resistance than those sintered in an argon atmosphere due to the formation of hard and brittle Cr₂N. The wear mechanisms of stainless steels against diamond were found to be mainly abrasive and oxidative. Semiquantitative analysis of the worn surfaces and wear debris confirmed the occurrence of oxidation processes during wear.     

Effect of 10 wt% VC on the Friction and Sliding Wear of Spark Plasma–Sintered WC–12 wt% Co Cemented Carbides

The effect of 10 wt% VC addition on the friction and sliding wear response of WC–12 wt% Co cemented carbides produced by spark plasma sintering (SPS) was studied. The SPS of WC–12 wt% Co alloys with and without 10 wt% VC, at 1100 and 1130°C, respectively, yielded dense materials with minimal porosity. No eta phase was found in any of the alloys. The WC–12 wt% Co–10 wt% VC alloy showed the formation of a hard WV₄C₅ phase, which improved the alloy's hardness. Friction and dry sliding wear tests were done using a ball-on-disk configuration under an applied load of 10 N and sliding speed of 0.26 m.s^?1, and a 100Cr-steel ball was used as the counterface. A significant improvement in the sliding wear response of the harder and more fracture tough WC–12 wt% Co–10 wt% VC alloy compared to the WC–12 wt% Co alloy was found. Analysis of the worn surfaces by scanning electron microscopy showed that the wear mechanisms included plastic deformation, preferential binder removal, adhesion, and carbide grain cracking and fragmentation.     

High temperature friction and wear mechanism map for tool steel and boron steel tribopair

Abstract

Tribological systems working under severe conditions like high pressures, sliding velocities and temperatures are subjected to different phenomena such as wear, oxidation and changes in mechanical properties. In many cases, there are several mechanisms occurring simultaneously. The predominating type(s) of wear mechanism(s) presented will depend on the materials in contact, operating parameters and surrounding environment. In this work, high temperature tribological studies of boron steel sliding against tool steel were conducted using a pin-on-disc machine under unlubricated conditions at five different temperatures ranging from 25 to 400°C, three different loads: 25, 50 and 75 N (contact pressures of 2, 4 and 6 MPa respectively) and a sliding speed of 0·2 ms^?1. Scanning electron microscopy/energy dispersive spectroscopy and X-ray techniques were used for analysing the resulting damage and tribolayers of the worn surfaces. Additionally, hardness measurements were carried out in a special hot hardness rig in the same temperature range as that used in pin-on-disc tests. The results have shown that for a given load, the wear rate of boron steel decreased as the temperature increased, reaching its lowest value at 400°C at 50 N. In the case of the tool steel, it could be observed that at 200°C and above, the wear rate decreased as the load increased. This behaviour is consistent with the formation of a protective oxidised layer initiated at 100°C. At higher temperatures, such layers become more pronounced. The obtained data were finally used to construct a friction and wear mechanism map for this material pair that takes temperature and pressure into account.     

铜锡铅锌合金的摩擦磨损性能

利用MMU-200型摩擦磨损试验机研究了铜锡铅锌合金与GCr15钢对磨时的摩擦磨损特性,利用扫描电子显微镜对合金的磨损表面形貌进行了观察。结果表明:铜锡铅锌合金的磨损率随载荷和摩擦速度的增加而增大;其摩擦因数随摩擦速度的增加而减小,随载荷的增加先增大后减小;其磨损机制主要为磨粒磨损和粘着磨损;合金中的铅相起到了润滑作用,有利于提高合金的耐磨性能。     

Tribological Performance of Boronized,Nitrided, and Normalized AISI 4140 Steel against Hydrogenated Diamond-Like Carbon-Coated AISI D2 Steel

In the current work, AISI 4140 steel was pack-boronized at 950°C for 3 h and gas-nitrided at 550°C for 72 h. All specimens used in this work were prepared from the same steel bar. A 3-µm-thick diamond-like carbon (DLC) coating (a-C:H) was deposited on the AISI D2 high-carbon, high-chromium, cold-worked tool steel by a plasma-assisted chemical vapor deposition technique. Normalized, boronized, and nitrided steel pins were tested against DLC-coated AISI D2 steel at various normal loads (15, 30, 60, and 80 N) for 1,000 and 3,000 m sliding distance in ambient air. Specific wear rate of all pins decreased with increasing load, and a similar trend was observed for the coefficient of friction (COF). Microscopic and energy-dispersive spectroscopic (EDS) analysis confirmed the role of the transfer layer for a low COF with increasing load. At all loads, the specific wear rate of boronized pins was lower than that of the nitrided and normalized pin specimens. Boronized pins showed a specific wear rate in the range of 0.27 × 10^?8 to 0.44 × 10^?8 mm³/Nm and the COF was about 0.1.     

铜碲硒铁合金的干摩擦磨损性能

利用环-盘式摩擦磨损试验机研究了铜碲硒铁合金的干摩擦磨损行为,分析了载荷和摩擦速度等参数对该合金摩擦磨损性能的影响,并用扫描电子显微镜对磨损形貌进行了观察.结果表明:铜碲硒铁合金的摩擦因数随载荷的增加变化不大,但随摩擦速度的增加而明显增大;合金的磨损率随载荷和摩擦速度的增加均增大;在轻载低速条件下,合金的磨损机制以犁削磨损和粘着磨损为主;在重载高速条件下,磨粒磨损和粘着磨损加剧.     

Friction and Wear Behavior of Irradiated Polyethylene Sliding Against a Rough Steel Surface

The aim of this study was to evaluate the tribological behavior of polyethylene crosslinked by gamma radiation sliding against a steel surface. Two high-density polyethylenes were irradiated to a total dose in the range of 2?20 Mrad under vacuum and at room temperature. After irradiation, the materials were annealed at 423 K and then cooled slowly to room temperature. The same thermal treatment was applied to the non-irradiated polymer. The wear behavior of the polymers was determined under controlled ambient temperature of 298 and 333 K using a homemade tribometer. Sheet-shaped specimens were loaded against the surface of a steel disc with different normal loads to generate nominal contact pressures in the range of 0.25–1.5 MPa. The tests were performed under dry conditions using a disc rotation to produce an average sliding speed of 0.6 m/s and during a period of time to provide an average sliding distance of 1,080 m. The wear rate was obtained as the mass loss by the sample divided by the sliding distance, and the friction coefficient was determined by measuring the friction force. The results indicate that the wear rate increases with load in the case of non-irradiated polyethylene and low-dose irradiated polymers, while the wear rate reaches a maximum value with the load in the case of the irradiated samples with high doses. The samples irradiated with a dose of 10 Mrad showed the lowest wear. The coefficient of friction (COF) increases slightly with the load in all the cases. Most irradiated polymers show higher COF than the non-irradiated material when compared at a given load. The results show that the irradiation dose applied to the polyethylenes produced no noticeable effect on the COF values when a comparison was made at a given applied load.     

Sliding Wear Characteristics of AZ91D Alloy at Ambient Temperatures of 25–200 °C

The dry sliding wear tests were performed for AZ91D alloy under the loads of 12.5–300 N and the ambient temperatures of 25–200 °C. We studied the wear characteristics of AZ91D alloy as a function of the normal load and the ambient temperature. The mild-to-severe wear transition occurred with increasing the load and the critical load reduced with the ambient temperature rising. However, no matter how high the ambient temperature was in the range of 25–200 °C, the mild wear prevailed under the lower loads. Especially, the AZ91D alloy presented a lower wear rate at 200 °C than at 25 and 100 °C under the low loads of 12.5–25 N, but vice versa under the loads of more than 25 N. These phenomena seem to be contradictory to the popular view that the mild-to-severe wear transition is controlled by the critical surface temperature. These may be attributed to a thick and hard mechanical mixing layer (MML) containing the mixture of MgAl₂O₄ and Mg on the worn surface. The MML thickened with increasing the ambient temperature (under the low loads), effectively reduced wear and markedly elevated the critical surface temperature. The oxidative wear and delamination wear successively predominated in the mild wear regime; the gross plastic-induced wear would prevail in the severe wear regime.