A comparison of the reciprocating sliding wear behaviour of steel based metal matrix composites processed from self-propagating high-temperature synthesised Fe–TiC and Fe–TiB2 masteralloys

Steel matrix particulate composites were processed by direct addition of various powders to molten medium carbon steel. Fe–TiC and Fe–TiB₂ powders were produced using a self-propagating high-temperature synthesis (SHS) reaction and consisted of a dispersion of fine TiC (5–10 μm) and TiB₂ particles (2–5 μm), respectively in an iron binder.Addition of the Fe–TiC powder to the steel resulted in the formation of a metal matrix composite containing a homogeneous dispersion of TiC particles. However, addition of the Fe–TiB₂ powder resulted in the formation of a parasitic Fe₂B phase and TiC within the steel microstructure. In response to this an SHS masteralloy composed of Fe–(50% TiB₂+50%Ti) was manufactured which, when added to steel, prevented the formation of Fe₂B and resulted in a composite containing a mixture of TiB₂ and TiC particles.Dry reciprocating sliding wear behaviour of the three composite materials and their unreinforced counterpart was investigated at room temperature against a white cast iron counterface. Relative wear behaviour of the materials varied as a function of load. In all cases, the composite manufactured by addition of Fe–TiB₂ (yielding Fe₂B and TiC phases in the steel) exhibited wear rates greater than three times that of the unreinforced alloy. However, improvements in wear resistance over the base steel of up to two and a half times were observed with the other composites where the desired TiC and/or TiB₂ phases were retained in the steel. Scanning electron microscopy has been used to interpret wear behaviour in relation to both the as-cast microstructures of the composites and the wear scar microstructures observed.     

Influence of plasma nitriding on fretting wear behaviour of Ti–6Al–4V

Plasma nitriding was performed on Ti–6Al–4V samples at 520 °C in two environments (pure nitrogen and a mixture of nitrogen and hydrogen in the ratio of 3:1) for two different time periods (4 and 18 h). Fretting wear tests were conducted on unnitrided and nitrided samples for 50,000 cycles using alumina ball counterbody. Plasma nitriding reduced the tangential force coefficient of Ti–6Al–4V. The samples nitrided for 4 h exhibited higher hardness and lower tangential force coefficient compared to the specimens nitrided for 18 h. The samples nitrided in nitrogen–hydrogen mixture environment exhibited higher hardness and lower tangential force coefficient compared to the specimens nitrided in pure nitrogen. The samples plasma nitrided in nitrogen–hydrogen mixture for 4 h exhibited the highest hardness and the lowest tangential force coefficient. The wear volume and specific wear rate of the plasma nitrided samples were lower than those of the unnitrided samples. A consistent trend was not observed regarding which nitriding condition would result in lower wear volume and specific wear rate at different loads.     

Sliding wear of 100Cr6 in a diesel-lubricated flat–flat contact under realistic loads

The tribological limits of martensitic AISI 52100 steel were determined by the application of a wear-mapping technique based on the statistical design of experiments. Wear measurements were conducted on a pin-on-disc system lubricated with a low-lubricity diesel fuel, with both pin and disc constructed of the same AISI 52100 steel. The test bench was equipped with a displacement transducer and an accurate temperature control of the samples temperature, enabling low wear rates to be measured in situ by the displacement transducer without being perturbed by thermal dilatation. By this method it is possible to measure wear rates on the order of a few nm/h. Moreover, the wear of the disc was evaluated at the end of each test by profilometry. A statistical model was fitted to the obtained results. Combining the findings of several surface characterisation methods, we identified two active wear mechanisms: tribocorrosion at low contact pressures (15 N/mm²) and adhesive wear at higher loads. This conclusion was corroborated by examinations of wear particles carried out by scanning electron microscopy and transmission electron microscopy.     

Analysis of dry sliding friction and wear behaviour of AA6351–SiC–B4C composites using grey relational analysis

Abstract

This paper describes the multifactor based experiments that are applied to investigate the dry sliding wear system of aluminium matrix alloy (AA6351) with 5 wt-% silicon carbide (SiC), 5 wt-% and 10 wt-% of boron carbide (B₄C) reinforced metal matrix composites (MMCs). Stir casting route was adopted to prepare the composites and the tribological experiments were carried out on pin-on-disc type wear machine. The effects of parameters like applied load, sliding velocity, wt-% of B₄C on the dry sliding wear and frictional coefficient of aluminium MMCs using grey relational analysis (GRA) are reported. The orthogonal array with L9 layout and analysis of variance were used to investigate the influence of the parameters. It is observed that the dry sliding friction and wear behaviour of the composites are influenced by the applied load, sliding velocity and wt-% of B₄C with a contribution of 60·82%, 21·72% and 14·28% respectively. The optimal design parameters were found by grey relational grade and a good agreement was observed for 95% level of confidence.     

Micro-abrasion wear testing of triode plasma diffusion and duplex treated Ti–6Al–4V alloy

In this paper micro-abrasion wear testing is used to evaluate the wear resistance of triode plasma diffusion-treated, single-layered TiN-, CrAlN-, and WC/C-coated and duplex-diffusion and coated Ti–6Al–4V under uniform three-body rolling abrasion. Nanoindentation, Knoop microhardness, mechanical surface profilometry, optical microscopy, scanning electron microscopy and atomic force microscopy, were used to characterise the surfaces under investigation. Optimum testing conditions for rolling abrasion were established by varying the test parameters and resultant severity of contact. Very low normal loads and high volume fractions of particles in the abrasive slurry are necessary to obtain predictable and reproducible results. Relatively coarse SiC abrasive particles, having a mean diameter of around 3 μm, appear more suitable for micro-abrasion testing of the samples investigated, compared to finer Al₂O₃ particles. Problems associated with the measurement of the scar volume and subsequent calculation of the wear rate for hard coatings deposited on relatively soft metals like titanium are identified, and suitable testing and measurement techniques are suggested. Three-dimensional wear scar maps generated by mechanical stylus profilometry were used to measure the wear volumes. Under the test conditions used, wear coefficients can be determined from perforating and non-perforating tests, although perforating tests provide more consistent results. Triode plasma diffusion treatments, plasma-assisted (PA) PVD TiN and PAPVD CrAlN can reduce the specific wear rate of Ti–6Al–4V, while PACVD-based WC/C coatings do not provide suitable protection against abrasive wear. The combination of triode plasma oxynitriding diffusion treatments and PVD coatings to create duplex treatments can also lead to further reductions in the coating wear coefficient when compared to non-duplex coatings deposited on non-pretreated substrates.     

Development of empirical model for abrasive wear volume of sisal fibre–epoxy composites

Abstract

In this paper, an empirical model was developed for high stress abrasive wear behaviour of unidirectional sisal fibre reinforced epoxy composites under varying operating parameters, for which a number of experiments were carried out to determine the abrasive wear behaviour of the composites. Polysulphide modified epoxy resin was used to make composites having three different sisal fibre concentrations in three different fibre orientations, namely longitudinal, transverse and normal. Abrasive wear of composites depends on operating parameters, such as applied load, grit size, sliding distance and weight percentage of sisal fibre. The abrasive wear data have been analysed using statistical analysis, and empirical relations are proposed.     

Influence of fiber orientation on abrasive wear of unidirectionally reinforced carbon fiber–polyetherimide composites

A composite with continuous carbon fibers (CF) (80% by vol.) and high performance thermoplastic polyetherimide (PEI) matrix was developed and evaluated for various mechanical properties as a function of fiber orientation angle (0°, 30°, 45°, 60° and 90°). It was observed that Young's modulus, Poisson's ratio, toughness and % strain decreased with the increase of fiber orientation angle with respect to loading direction. In-plane shear modulus was highest for fibers with 45°. Overall, unidirectional (UD) CF reinforcement enhanced all strength properties of PEI significantly. Composites with fibers in 0° (parallel to loading direction) proved best in almost all the properties. Tribological evaluation in abrasive wear mode under different loads and fiber orientations indicated that coefficient of friction (μ) and specific wear rate (K₀) decreased with load, in general. Comparatively low specific wear rate (K₀), (in the order of 0.7 1×10^?9 m³/Nm) was observed for 0° fiber orientation, while fibers in 90° showed almost three times higher wear rate. Overall fiber reinforcement in 0° orientations proved beneficial from both strength and tribological performance point of view. SEM proved useful to correlate wear rate with surface topography.     

Corrosion and corrosion wear behaviour of plasma carburised Stellite 21 Co–Cr alloy

Abstract

Low temperature plasma surface alloying with carbon (i.e. plasma carburising) of Stellite 21 Co–Cr alloy was conducted at temperatures from 400 to 500°C for 15 h in a gas mixture of 98 vol.-%H₂ and 2 vol.-%CH₄. The surface treated layers were characterised by XRD, SEM and microhardness tests. The corrosion and corrosive wear behaviour of the plasma carburised Stellite 21 Co–Cr alloy were studied respectively using electrochemical tests and well designed reciprocating wear tests in 3·5% NaCl solution. The results show that low temperature (≤460°C) plasma carburising can improve the corrosion resistance of Stellite 21 alloy; the corrosive wear resistance of Stellite 21 can be enhanced by up to three times; and the best corrosive wear resistance is achieved at the highest treating temperature (500°C). The detailed studies on the wear tracks indicate that the corrosive wear process was dependent on the individual wear and corrosion, as well as the synergetic effect.     

Tribological behaviour of SiC?TiC?TiB2 composites under unlubricated sliding conditions

The friction and wear behaviour of eight different SiC TiC TiB₂ composite materials, with a practically constant SiC:TiC ratio of 1 and an increasing amount of TiB₂, was determined comparatively in oscillating sliding tests at room temperature under unlubricated conditions. The influence of the relative humidity (RH) of the surrounding air was investigated in tests in dry, normal, and moist air. All tests were performed against SiC balls and Al₂O₃ balls as counterbodies. The friction was affected by RH but barely at all by the composition of the composites. The wear resistance of the composites was found to be improved considerably by addition of TiB₂ in the range 20–60%. The highest wear resistance of the system was found when Al₂O₃ was used as the counterbody material.     

Effect of silicon content on wear resistance and corrosion behaviour of Al–Si eutectic alloy

Abstract

In the present study, Al–Si eutectic alloys produced at the Aluminium Institution were studied. The alloys were cast and forged into bars of 20 mm diameter. The results obtained were compared with a pure aluminium sample. Metallographic analysis, spectral analysis, SEM and energy dispersive spectroscopy analysis, pin on disk abrasive wear tests and mass loss tests were performed. Wear resistances of alloys with various silicon contents were tested under different loads and constant abrasive speed. SiC abrasive paper of 80 grit size was used. The dry sliding tests were carried out under loads of 10, 20 and 30 N and the testing was conducted under a constant sliding velocity of 36˙8 m min^–1 in a dry air atmosphere. Corrosion rates were determined in 0˙1M NaCl acid solutions. The corrosion tests were performed at 2, 4, 6 and 8 h. The wear and corrosion resistance of all the eutectic alloys increased with increasing silicon content in the matrix.     

Influence of turning parameters on the machinability of homogenized Al–Cu/TiB2 in situ metal matrix composites

The increasing demand for high-strength and lightweight materials in automobile, defense, and aerospace applications necessitates the development of new composite materials and their machinability studies with wide spectrum. In this aspect, an attempt has been made to investigate the machinability characteristics of homogenized Al–Cu/TiB₂ in situ metal matrix composites. The effect of parameters, such as cutting speed, feed, and depth of cut, on performance measures, such as cutting force and surface roughness, were investigated during turning operations. As a secondary objective, the built-up edge (BUE) and chip formation are also examined. Experimental results show that better surface finish is obtained at higher cutting speed and low feed. BUE formation is observed only at low cutting speed. The chip breakability is improved due to the presence of reinforcement.     

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.     

Effect of CNFs content on the tribological behaviour of spark plasma sintering ceramic–CNFs composites

Alumina-carbon nanofibres (CNFs) and silicon carbide–CNFs nanocomposites with different volume fraction of CNFs (0–100 vol.%) were obtained by spark plasma sintering. The effect of CNFs content on the tribological behaviour in dry sliding conditions on the ceramic–carbon nanocomposites has been investigated using the ball-on-disk technique against alumina balls. The wear rate of ceramic–CNFs nanocomposites decreases with CNFs increasing content. The friction coefficient of the Al₂O₃/CNFs and SiC/CNFs nanocomposites with high CNFs content was found to be significantly lower compared to monolithic Al₂O₃ and SiC due to the effect of CNFs and unexpectedly slightly lower than CNFs material. The main wear mechanism in the nanocomposite was abrasion of the ceramic and carbon components which act in the interface as a sort of lubricating media. The experimental results demonstrate that the addition of CNFs to the ceramic composites significantly reduces friction coefficient and wear rate, resulting in suitable materials for unlubricated tribological applications.     

Dry sliding wear behaviour of Ti–6Al–4V pin against SS316L disc in vacuum condition at high temperature

ABSTRACT

Ti–6Al–4V alloy exhibit a unique combination of mechanical, physical, and chemical properties; that pronounced its desirability for implementation in the fields of aerospace, automobile, and chemical industries. The mechanisms, namely, strain rate response/adiabatic shear band (ASB) – effect of plastic deformation, tribo-chemical reaction and formation of the mechanically mixed layer (MML), can control wear behaviour of the alloy. Hence, the present work investigates the influence of these mechanisms in governing the tribological characteristics of the Ti6Al4V alloy aganist SS316L steel. The experiments were executed on a pin-on-disc tribometer under vacuum (2?×?10^?5?Torr), by varying the temperature (25, 100, 200, 300 and 400°C) at constant sliding speed (0.01?ms^?1) and load (137.3?N) conditions. Compression test was carried out at distinct strain rate (0.001 and 10 s^?1) and temperature (25, 100 and 400°C) values, to investigate the occurrence of ASB. The scanning electron microscopy and energy dispersive X-ray spectroscopy analyses were used to evaluate the formation of appendage layers (oxides and MML) and the composition of wear debris, respectively. The wear rate of the Ti–6Al–4V alloy decreased with increment in temperature (room condition to 400°C) inside vacuum environ, governed by ASB and the presence of oxide layers.     

Sliding friction and wear of Cu–graphite against 2024, AZ91D and Ti6Al4V at different speeds

Cu–graphite composite fabricated by powder metallurgy art is no longer novel material. However, it might be a versatile self-lubricating material sliding against different metals and alloys. In this connection, understanding towards its tribological behavior and wear mechanism is very important. Sliding tribological behaviors of Cu–graphite composite against different counterparts, specified as 2024 aluminium alloy, AZ91D magnesium alloy, and Ti6Al4V titanium alloy, were investigated over varied sliding speeds at room temperature in air. The friction and wear tests were conducted on a pin-on-disk tribo-meter. Tribological performance of Cu–graphite composite strongly depended on its counterpart materials. Cu–graphite composite could provide friction reduction in sliding against 2024 and Ti6Al4V. Cu–graphite composite was a good self-lubricating material in sliding against AZ91D at low speeds but not at 0.25 and 0.50 m/s. Wear mechanism of Cu–Gr composite was related to the transfer, counter-transfer, mechanical mixing and tribo-oxidation at tribo-interface. Sliding speed had influences on tribo-interface and thereby wear mechanism. Finally, the effects of naturally occurred oxide film and sliding speed were discussed.     

Mild Sliding Wear of Fe–0.2%C,Ti–6%Al–4%V and Al-7072: A Comparative Study

The mild sliding wear of Fe–0.2%C, Ti–6%Al–4%V and Al-7072 was investigated by means of pin-on-disc sliding tests. The applied pressure was 1 MPa and the sliding velocity was varied between 0.2 and 1 m/s. The sliding behaviour was followed by continuous measurements of the friction coefficient, pin wear and pin temperature. For the Fe alloy, wear was mixed (delamination and oxidation), and friction and wear coefficients were found to decrease with sliding velocity. The Al and Ti alloys displayed a different behaviour, characterised by the occurrence of sliding distance transitions at 0.8 and 1 m/s for the Al alloy, and at 0.4 up to 1 m/s for the Ti alloy. Before the transition, the wear coefficient of the Al alloy was very low, because of the presence of a compacted tribolayer on the sliding surface. After the transition wear was by delamination: the wear rate increased but the friction coefficient decreased. For the Ti alloy, wear occurred by oxidation and was quite high before the transition. After the transition, both the wear rate and the friction coefficient decreased, although the wear process became unstable with repeated oscillations in the friction coefficient. The results allowed us to highlight the role of flash temperature in determining the wear mechanisms of the alloys under study and the necessity of properly considering the sliding distance transitions to make reliable comparisons and obtain guidelines for safe operations.     

Effects of cold working and heat treatment on microstructure and wear behaviour of Cu–Be alloy C17200

The effects of cold work process between aging and solution heat treatment on the microstructure, hardness and the tribologic behaviour of a copper–beryllium (Cu–Be) alloy C17200 were investigated. The wear behaviour of the alloys was studied using ‘pin on disc’ method under dry conditions. The results show that the formation of fine grained structure and γ phase particles enhances the mechanical properties of the alloy; nonetheless, they do not reduce the wear rate. This is attributed to the capability of the softer specimens to maintain oxygen rich compounds during the dry sliding test.     

A study on the wear of silicon nitride in rolling–sliding contact

The aim of this study is to characterize the wear in silicon nitride rolls undergoing rolling–sliding contact. A rolling contact experiment was proposed and conducted on a twin-disk tribometer. The ceramic rolls were brought into rolling contact with hardened steel disks under water lubrication at a predefined slip ratio. The generated wear on the surface of the rolls was measured and converted into a wear coefficient, which was subsequently implemented in a finite element based simulation to estimate the influence of geometrical variations on the contact stresses.The results show that wear in silicon nitride was numerically simulated to an acceptable accuracy by relying on a simple mathematical model. A correlation among progressive wear, contact stress fields and surface crack propagation patterns was established.     

A micro-contact and wear model for chemical–mechanical polishing of silicon wafers

A micro-contact and wear model for chemical–mechanical polishing (CMP) of silicon wafers is presented in this paper. The model is developed on the basis of elastic–plastic micro-contact mechanics and abrasive wear theory. The synergetic effects of mechanical and chemical actions are formulated into the model. A close-form equation of material removal rate from the wafer surface is derived relating to the material, geometric, chemical and operating parameters in a CMP process. The model is evaluated by comparing the theoretical removal rates with those experimentally determined. Good agreement is obtained for both chemically active and inactive polishing processes. The model reveals some insights into the micro-contact and wear mechanisms of the CMP process. It suggests that the removal rate is sensitive to the particle concentration in the slurry, more sensitive to the applied load and operating speed and most sensitive to the surface hardness and slurry particle size. The model may be used to study the effects of different materials, geometry, slurry chemistry and operating conditions on CMP processes.     

A new method to investigate the sliding wear behaviour of materials based on energy dissipation: W–25 wt%Cu composite

A new method is proposed to explain and monitor wear behaviour based on energy dissipation. The wear of a W–25 wt%Cu composite against 52100 steel was used to demonstrate this approach with pin-on-disc tests conducted under three normal loads. An energy-dependent criterion, namely, specific wear volume (wear volume/dissipated energy (mm³/J)), was defined to evaluate the wear of the composite. The specific wear volume can be used as a substitute for the traditional wear rate due to the simultaneous expression of several wear parameters and because of its strong dependence on the wear mode. The specific wear volume appears to be constant in any particular “wear mode” regardless of the active “wear processes”. In the wear of this composite, processes such as particle pull-out, mechanically mixed layer (MML) formation, crack propagation and delamination were observed. But, combination of these processes in each test had identical specific wear volumes. Thus, all of these wear processes were considered to be consecutive stages of the same wear mode: fatigue wear. The amount of dissipated energy and the volumetric loss increased with increasing normal load. Also, changing the normal load changed the rate of energy dissipation per unit sliding distance.