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.     

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.     

Wear Behaviour of In Situ Al/TiB<Subscript>2</Subscript> Composite: Influence of the Microstructural Instability

In this present work, the in situ Al (A380)/5 wt%TiB₂ composites were fabricated through salt–melt reaction using halide salts such as potassium hexafluorotitanate (K₂TiF₆) and potassium tetra fluoroborate (KBF₄) salts as precursors. The composites were produced at four different melt temperatures (700, 750, 800, 850 °C). The formation of particle was confirmed from XRD results. The wear behaviour of Al/5 wt% TiB₂ composite was investigated by varying the wear test parameters such as sliding temperature (25, 100, 150, 200 °C), applied load (10, 20, 30, 40 N), sliding velocity (0.4, 0.7, 1, 1.3 m/s). The microstructure of Al/5 wt% TiB₂ composite was correlated with the wear characteristics of the composites. The wear resistance of Al/5 wt% TiB₂ composite was significantly improved due to the presence of TiB₂ particle in Al matrix material. The composite produced at melt temperature 800 °C showed a higher wear resistance at applied load: 10 N, sliding temperature: 25 °C and sliding velocity: 0.7 m/s. The wear mechanism for each of the tested condition was identified from the worn surfaces using scanning electron microscopy (SEM). ANOVA test was carried out to find out significant factor for the wear resistance of composite. The checking of adequacy of experimental value for the wear behaviour of composite for different testing condition was analysed by residual plots using statistical software.     

Role of zirconium diboride particles on microstructure and wear behaviour of AA7075 in situ aluminium matrix composites at elevated temperature

ABSTRACT

The present research work examines the impact of temperature on the dry sliding wear behaviour of AA7075 aluminium strengthened zirconium diboride (ZrB₂) particulate composite (0, 3, 6, 9 and 12?wt.%). The dry sliding wear behaviour of the AMCs was inspected utilizing a pin-on-disc machine at differing temperatures (40, 60, 120, 180 and 240°C). The wear resistance of AMCs improved with the increased substance of ZrB₂ particulates at all test temperatures. The worn surface of the AMC pins was described utilizing FESEM. It was found from the SEM micrographs of worn surface, that at different temperatures, adhesion and metal flow were the prime wear process of the AA7075 composites, while for in situ formed AMCs, metal stream and oxidation were the factors affecting the wear process. The worn surface of the AMCs showed that there was a modification in wear component from abrasive wear to metal flow.     

Wear reducing effects and temperature dependence of tribolayer formation in harsh environment

Certain materials show a tribolayer formation especially at enhanced temperatures in abrasive environment, building a wear protection layer with the abrasive on the surface. Three materials with different microstructures were tested in three-body abrasive and impact/abrasive environments at temperatures up to 700 °C to investigate tribolayer formation. Optical and electron microscopical methods were used for wear qualification. Furthermore, hot hardness tests were performed up to 700 °C to investigate the influence of hardness drop on tribolayer formation.It was shown that no significant tribolayer formation occurs on grey cast iron, whereas other materials form tribolayers. Generally, tribolayer formation increases with increasing testing temperature, especially for austenitic and ferritic materials. This entails a self-protecting effect and thus superior wear resistance in abrasive environment.     

Tribological behaviour of carbide-free bainitic steel under dry rolling/sliding conditions

The dry rolling/sliding wear behaviour of Si alloyed carbide free bainitic steel austempered at different temperatures and sliding distances has been evaluated. 60SiCr7 spring steel samples were austempered in a salt bath maintained at 250, 300 and 350 °C respectively for 1 h. Rolling with 5% sliding wear tests were performed using self mated discs for three different test cycles, namely 6000, 18,000 and 30,000 cycles. The aim was to study the wear performance of the 60SiCr7 steel with a carbide-free microstructure containing different amounts of retained austenite. An in-depth microstructural characterization has been carried out before and after the wear tests in order to link the wear behaviour to the microstructure of each sample. The wear resistance has been expressed by means of the specific wear calculated from the mass loss after the tests. The worn surfaces were analysed by scanning electron microscopy and X-ray diffraction. Microhardness profiles were also obtained in order to analyse strain-hardening effects beneath the contact surfaces. The results indicate that the material with highest hardness—the one austempered at 250 °C—exhibited the lowest wear rate in every case. It was also observed that the hardness increment and thickness of the hardened layer increases with increasing the austempering temperature and number of test cycles. Finally, the results appear to indicate that the initial roughness of the samples has no major effect in the wear rate of the samples above 2500 cycles. The higher wear performance of the sample austempered at 250 °C has been attributed to its superior mechanical properties provided by its finer microstructure. It has been evidenced that all samples undergo the TRIP phenomenon since, after wear; no retained austenite could be detected by XRD.     

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.     

Reciprocating Sliding Wear Behavior of 60NiTi As Compared to 440C Steel under Lubricated and Unlubricated Conditions

ABSTRACT

60NiTi is a hard (～60 HRC) and highly corrosion-resistant intermetallic with a relatively low elastic modulus (～100 GPa). In addition, this alloy exhibits a high compressive strength (～2,500 MPa) and a high elastic compressive strain of over 5%. These attributes make this alloy an attractive candidate to be employed in structural and mechanical component applications. However, sliding wear behavior of this intermetallic has not yet been studied in a systematic way. In this study, lubricated and unlubricated reciprocating sliding wear behavior of 60NiTi is compared to 440 C steel as a conventional bearing and wear-resistant alloy. Results of experiments carried out under different loads show that 60NiTi, despite having a higher hardness, exhibits a significantly inferior wear behavior under dry conditions in comparison to 440 C steel. These unexpected results indicate that 60NiTi does not follow conventional wear theories where the wear of materials has an inverse relationship to their hardness. On the other hand, under lubricated conditions with castor oil and a synthetic gear oil, 60NiTi exhibits low specific wear rates. These results exhibit the importance of proper lubrication in sliding mode applications where 60NiTi is exploited as a wear-resistant alloy.     

Influence of Combined Addition of Boron and Strontium on High-Temperature Wear Behavior of A356 Alloy

In the present study, the effect of the combined addition of boron (B) and strontium (Sr) on the high-temperature dry sliding wear behavior of A356 alloy has been investigated using a pin-on-disc wear testing machine attached with a furnace. During wear studies, the effect of alloy composition, normal pressure, sliding speed, and sliding distance on A356 alloy at four temperatures, namely, room temperature and 100, 200, and 300°C, have been investigated. Further, the cast alloys and worn surfaces of A356 alloy with and without B and Sr were characterized by scanning electron microscopy (SEM)/energy-dispersive spectroscopy (EDS) microanalysis. Results indicate that the combined addition of B and Sr to A356 alloy has led to improvements in wear properties. This is due to a change in microstructure, improvement in mechanical properties, and the formation of an oxide layer between the mating surfaces during the sliding wear process.     

Further investigation on the tribological behavior of Al2O3–20Ag20CaF2 composite at 650°C

The friction and wear behaviors of the self‐lubricating Al₂O₃–20Ag20CaF₂ disk against an Al₂O₃ pin pair have been investigated over a broad load range from 1 to 30 N and sliding velocities from 0.084 to 1 m/s at 650^°C. Four typical wear modes have been identified and the wear mode map was constructed to illustrate the influence of load and speed on the friction coefficient and wear rate. The results showed the effective self‐lubricating region (II) (continuous lubricating film) is almost independent of sliding speed, and mainly dependent on the load. It is suggested that the plastic deformation and plastic flow during sliding play an important role in the formation of the self‐lubricating film on the sliding surface. Furthermore, the worn surface in the region (II) (continuous lubricating film) was found to be much softer than the original surface and the distribution of Vickers hardness became more uniform due to the presence of the lubricating film on the worn surface. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of cryogenic treatment on the tribological behaviour of H11 hot die steel dry sliding against D3 steel

The tribological behaviour, hardness and microstructural characteristics of vacuum and cryogenically treated AISI H11 steel at varied soaking temperature (?154 and ?184 °C) for specific time period (6, 21 and 36 h) have been examined in this research work. The influence of selected parameters on the tribological behaviour have been studied at five levels of varying sliding velocities (0.628–1.885 m/s) and normal loads (60–140 N) through block–on–ring dry sliding wear test against hardened and tempered AISI D3 tool steel (counter face). The experiments are designed based on full factorial response surface methodology. The responses (wear rate, average coefficient of friction and maximum contact temperature) are analyzed based on plotted graphs. The results reveal that 21 h at ?184 °C for H11steel is the optimal soak time to have the lowest wear rate. The sliding speed influences the wear rate more in comparison to load. Wear debris have shape of metallic plate. Carbide particles appeared to delaminate from the sample surface due to subsurface cracks and plastic deformation. The augmentation of apparent and bulk hardness number and wear resistance ascribed to the increase in number of fine globular secondary carbide and improved morphology of matrix microstructure of cryogenic-treated sample. It is also observed that cryogenic treatment reduces the retained austenite content to near zero.     

Effects of temperature and sliding distance on the wear behavior of austenitic Fe-Cr-C-Si hardfacing alloy

The effects of temperature and sliding distance on the metal-to-metal wear behavior of austenitic Fe-20Cr-1.7C-1Si hardfacing alloy were investigated in air in the temperature range from 25 to 450 °C. The applied contact stress was 55 MPa and the maximum sliding distance was 18 m. In the temperature range from 25 to 200 °C, the weight loss increased linearly with increasing sliding distance. The weight loss increased parabolically with increasing sliding distance up to 18 m at 300 °C, but at 450 °C, the weight loss drastically increased from the beginning of the wear test and became almost saturated above a sliding distance of 3.6 m. The initial friction coefficient was not changed with temperature up to 300 °C. However, at 450 °C, the initial friction coefficient increased abruptly. It was thought to be due to the increasing tendency of adhesive bonding to occur between the two self-mating specimens. At temperatures below 200 °C, the steady state friction coefficient did not change significantly. Above 300 °C, the steady state friction coefficient decreased due to the oxide layers that formed on the worn surfaces during wear.     

A study on wear and worn surfaces of grey cast iron affected by a novel silicate additive

A novel aluminium silicate hydroxide additive has shown excellent anti‐wear effect in practical applications and has been mainly studied on steels in laboratory conditions. In this paper, the pin‐on‐disk sliding wear tests were carried out to investigate the wear and worn surfaces of grey cast iron with additives in different concentration. It was found that the silicate additive showed an obvious anti‐wear effect and a reliable duration, reduced the number of pits and cracks on the worn surfaces and improved the nanohardness of the worn surfaces of grey cast iron disks by 72%. Furthermore, Raman spectroscopy displayed that the carbon structure of the worn surface of grey cast iron disks with the additive had an obvious transformation from nanocrystalline graphite to amorphous carbon. Copyright © 2015 John Wiley & Sons, Ltd.     

Severe-to-Mild Wear Transition of Titanium Alloys as a Function of Temperature

Dry sliding wear behaviors of Ti–6Al–4V and Ti–6.5Al–3.5Mo–1.5Zr–0.3Si alloys (code-named TC4 and TC11, respectively) against AISI 52100 steel under a load of 50–250 N at 25–600 °C were systematically investigated. For two titanium alloys, a severe-to-mild wear transition occurred with an increase in temperature. The critical transition temperatures of TC4 and TC11 alloys were 400 and 300 °C, respectively. Below the critical temperature, titanium alloys showed poor wear performance. As the temperature surpassed the critical temperature, the extremely low wear rates demonstrated excellent elevated-temperature wear performance of titanium alloys in the titanium alloy/steel tribo-system. The wear transition was characterized with the appearance of continuous, hard tribo-layer containing more oxides, especially Fe₂O₃, which showed a pronounced wear-reduced role. Adhesive and abrasive wear predominated in the severe wear regime; oxidative mild wear prevailed in the mild wear regime. Adhesive wear, abrasive wear and oxidative mild wear cooperated at the critical transition temperatures.     

Wear behaviour of in situ Cu–Al2O3 composites produced by internal oxidation of as cast alloys

Abstract

In the present study, the wear behaviour of Cu–Al₂O₃ composites and Cu–Al alloys has been investigated. The experiment involved casting of Cu–Al alloys with 0·37, 1, 2 and 3 wt-% of aluminium under inert gas atmosphere. The composites were produced by internal oxidation of alloys at 950°C for 10 h in presence of Fe₂O₃ and Al₂O₃ powders mixture. The microstructures of composites were studied using SEM and atomic force microscopy. To identify wear behaviour of specimens, dry sliding pin-on-disk wear tests were conducted according to ASTM G99-95a standard. The normal loads of 20, 30, and 40 N were applied on specimens during wear tests. The sliding speed and distances were selected as 0·5 m s^–1 and 500, 1000 and 1500 m respectively. To specify the wear mechanisms, the worn surfaces of composites were examined by SEM equipped with EDX. According to wear test results, increasing applied load and sliding distance leads to more volume loss in all specimens. Composites represent better wear resistance in comparison to alloys. Additionally, increasing the volume fraction of alumina particles in composites enhances the wear resistance, especially under high applied load. The wear mechanisms are mainly abrasion, oxidation and delamination.     

Tribological Characteristics of Calophyllum inophyllum–Based TMP (Trimethylolpropane) Ester as Energy-Saving and Biodegradable Lubricant

The purpose of this research is an experimental study of Calophyllum inophyllum (CI)-based trymethylolpropane (TMP) ester as an energy-saving and biodegradable lubricant and compare it with commercial lubricant and paraffin mineral oil using a four-ball tribometer. CI-based TMP ester is a renewable lubricant that is nonedible, biodegradable, and nontoxic and has net zero greenhouse gases. The TMP ester was produced from CI oil, which has high lubricity properties such as higher density, higher viscosity at both 40°C and 100°C and higher viscosity index (VI). Experiments were conducted during 3,600 s with constant load of 40 kg and constant sliding speed of 1,200 rpm at temperatures of 50, 60, 70, 80, 90, and 100°C for all three types of lubricant. The results show that CI TMP ester had the lowest coefficient of friction (COF) as well as lower consumption of energy at all test temperatures, but the worn surface roughness average (R_a) and wear scar diameter were higher compared to paraffin mineral oil and commercial lubricant. Before 80°C, CI TMP ester actually has a higher flash temperature parameter (FTP) than paraffin mineral oil and as the temperature increases, the FTP of TMP ester decreases. The worn surfaces of the stationary balls were analyzed by scanning electron microscopy (SEM) and results show that CI TMP ester has the highest wear compared to paraffin mineral oil and lowest wear compared to commercial lubricant. However, CI TMP ester is environmentally desired, competitive to commercial lubricant, and its use should be encouraged.     

Microstructure and Wear Behavior of a Manganese Bronze Bearing Material under Unlubricated Conditions

In an attempt to collect information about the tribological performance of copper-based bearings, the friction and wear behaviors of C86300 manganese bronze were investigated. The characteristics of the base material were determined by structural and mechanical investigations. Then, dry sliding pin-on-disc wear tests were performed against an AISI 52100 steel counterface. After the wear tests, the worn surfaces of the pins and wear debris were studied by scanning electron microscopy and energy-dispersive X-ray spectroscopy. In addition, light optical microscopy and microhardness measurements were performed for examination of the steel counterfaces and worn pin subsurface layers. With increasing normal load, the wear rate of commercial C86300 alloy (containing 0.6 wt% Si) decreased initially and then began to increase. After reaching a maximum wear rate at the load of about 60 N, the wear rate decreased again with a further increase in the normal load. However, the wear rate of this C86300 alloy mainly decreased with increasing sliding speed. Adhesive and abrasive wear were the dominant wear mechanisms under the designed conditions.     

The influence of heat treatment on the sliding wear behavior of a ZA-27 alloy

The effects of heat treatment, involving solutionizing at temperature of 370 °C for a relatively short period of time (3 or 5 h), followed by quenching in water, on tribological behavior of ZA-27 alloys were examined.Dry sliding wear tests were conducted on as-cast and heat-treated ZA-27 samples using block-on-disk machine over a wide range of applied loads. To determine the wear mechanisms, the worn surfaces of the samples were examined by scanning electron microscopy (SEM). The tribological results were related to the microstructure and mechanical properties.The heat treatment resulted in reduction in the hardness and tensile strength but increase in elongation. The heat-treated alloy samples attained improved tribological behavior over the as-cast ones, both from the aspects of friction and wear. The improved tribological behavior of the heat-treated alloys, in spite of reduced hardness, could be the result of breaking the dendrite structure, when the fraction of interdendrite regions was considerably decreased and a very fine α and η mixture was formed at the same time. The wear response of the samples has been corroborated through characteristics of worn surfaces and dominant wear mechanisms.     

Microstructural and Tribological Characterization of Stainless Steel–Reinforced Aluminum Matrix Bimetal Composites Produced at Various Mold Burnout Temperatures

This study aims to identify the optimal burnout temperature (BT) of a plaster mold that was used in bimetal composite production. To achieve this goal, the mold was gradually heated up to 600, 650, 700, and 750?°C prior to melt infiltration casting. Molten A356 aluminum alloy was cast into mold at 730?°C for each casting process. Fifty percent porous 304 stainless steel (SS) preforms, obtained by assembling recycled SS shavings, were placed in a mold and infiltrated by A356 alloy until solidification was completed. The produced bimetal composites were subjected to a ball-on-disc tribometer with loads of 5, 10, and 15 N for 100 m sliding distance using an Al₂O₃ ball as a counterpart. θ-Fe₄Al₁₃ and η-Fe₂Al₅ phases were formed at A356 Al–304 SS interfaces for all samples. Wear rates increased with increasing load and decreased with increasing BT, except at 750?°C. At this temperature, interfacial phases with excessively increased layer thickness, hardness, and brittleness were fragmentized during the test, and these cracked particles decreased wear resistance by participating in the wear process. The most suitable BT of the mold was found to be 700?°C, considering the microstructure and wear results of bimetal composites.     

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.