Dry sliding wear characteristics of glass–epoxy composite filled with silicon carbide and graphite particles

The dry sliding wear characteristics of a glass–epoxy (G–E) composite, filled with both silicon carbide (SiC_p) and graphite (Gr), were studied using a pin-on-disc test apparatus. The specific wear rate was determined as a function of sliding velocity, applied load and sliding distance. The laminates were fabricated by the hand lay-up technique. The volume percentage of filler materials in the composite was varied, silicon carbide was varied from 5 to 10% whereas graphite was kept constant at 5%. The excellent wear resistance was obtained with glass–epoxy containing fillers. The transfer film formed on the counter surface was confirmed to be effective in improving the wear characteristics of filled G–E composites. The influence of applied load is more on specific wear rate compared to the other two wear parameters. The worn surfaces of composites were examined with scanning electron microscopy (SEM) to investigate the probable wear mechanisms. It was found that in the early stage of wear, the fillers contribution is significant. The process of transfer film, debris formation and fiber breakage accounts for the wear at much later stages.     

Tribological behaviour of carbon–carbon composite

Abstract

In the present study, the wear behaviour of cross ply (0/90°) C–C composite with 60 vol.-% fibres has been studied with sliding distance, applied load and sliding velocities. The measurement of specimen temperature has been carried out to study the effect of frictional heating. Furthermore, wear debris and wear track observations are correlated to understand the wear mechanism. The bulk wear increases linearly with distance after an initial running-in period. The temperature studies reveal that frictional heating is more with increase in load or sliding velocity under dry conditions, however, presence of lubrication reduces frictional heating, because exposure of surface for direct contact is reduced, and hence wear rate in all studies with lubrication is less than that under dry condition. The wear track studies show graphite powder, peeling of fibres and dislodging of the surface. At low loads, smearing of graphite powder keeps the wear rate low, but as the load increases; dislodging, delamination of surface and breaking of fibres dominate, and wear rate sharply increases, however, sliding velocity initially enhances the graphite formation reducing the wear, but as the velocity reached an optimum value, there is extensive breakage of fibres, dislodging and delamination of surface, and the wear rate increases sharply.     

Dry Sliding Friction and Wear Characteristics of Cu-Sn Alloy Containing Molybdenum Disulfide

The wear and sliding friction response of a hybrid copper metal matrix composite reinforced with 10 wt% of tin (Sn) and soft solid lubricant (1, 5, and 7 wt% of MoS₂) fabricated by a powder metallurgy route was investigated. The influence of the percentages of reinforcement, load, sliding speed, and sliding distance on both the wear and friction coefficient were studied. The wear test with an experimental plan of six loads (5–30 N) and five sliding speeds (0.5–2.5 m/s) was conducted on a pin-on-disc machine to record loss in mass due to wear for two total sliding distances of 1,000 and 2,000 m. The results showed that the specific wear rate of the composites increased at room temperature with sliding distance and decreased with load. The wear resistance of the hybrid composite containing 7 wt% MoS₂ was superior to that of the other composites. It was also observed that the specific wear rates of the composites decreased with the addition of MoS₂. The 7 wt% MoS₂ composites exhibited a very low coefficient of friction of 0.35. The hardness of the composite increased as the weight percentage of MoS₂ increased. The wear and friction coefficient were mainly influenced by both the percentage of reinforcement and the load applied. Wear morphology was also studied using scanning electron microscopy and energy-dispersive X-ray analysis.     

Investigations on the influence of graphite filler on dry sliding wear and abrasive wear behaviour of carbon fabric reinforced epoxy composites

In this experimental study, the dry sliding wear and two-body abrasive wear behaviour of graphite filled carbon fabric reinforced epoxy composites were investigated. Carbon fabric reinforced epoxy composite was used as a reference material. Sliding wear experiments were conducted using a pin-on-disc wear tester under dry contact condition. Mass loss was determined as a function of sliding velocity for loads of 25, 50, 75, and 100 N at a constant sliding distance of 6000 m. Two-body abrasive wear experiments were performed under multi-pass condition using silicon carbide (SiC) of 150 and 320 grit abrasive papers. The effects of abrading distance and different loads have been studied. Abrasive wear volume and specific wear rate as a function of applied normal load and abrading distance were also determined.The results show that in dry sliding wear situations, for increased load and sliding velocity, higher wear loss was recorded. The excellent wear characteristics were obtained with carbon-epoxy containing graphite as filler. Especially, 10 wt.% of graphite in carbon-epoxy gave a low wear rate. A graphite surface film formed on the counterface was confirmed to be effective in improving the wear characteristics of graphite filled carbon-epoxy composites. In case of two-body abrasive wear, the wear volume increases with increasing load/abrading distance. Experimental results showed the type of counterface (hardened steel disc and SiC paper) material greatly influences the wear behaviour of the composites. Wear mechanisms of the composites were investigated using scanning electron microscopy. Wear of carbon-epoxy composite was found to be mainly due to a microcracking and fiber fracture mechanisms. It was found that the microcracking mechanism had been caused by progressive surface damage. Further, it was also noticed that carbon-epoxy composite wear is reduced to a greater extent by addition of the graphite filler, in which wear was dominated by microplowing/microcutting mechanisms instead of microcracking.     

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.     

Dry sliding wear behaviour of cast high strength aluminium alloy (Al–Zn–Mg) and hard particle composites

This paper describes the results of dry sliding wear tests of aluminium alloy (Al–Zn–Mg) and aluminium (Al–Zn–Mg)–10, 15 and 25 wt.% SiCp composite was examined under varying applied pressure (0.2 to 2.0 MPa) at a fixed sliding speed of 3.35 m/s. The sliding wear behaviour was studied using pin-on-disc apparatus against EN32 steel counter surface, giving emphasis on the parameters such as coefficient of friction, rise in temperature, wear and seizure resistance as a function of sliding distance and applied pressure. It was observed that the wear rate of the alloy was noted to be significantly higher than that of the composite and is suppressed further due to addition of silicon carbide particles. The temperature rise near the contacting surfaces and the coefficient of friction followed reversed trend. Detailed studies of wear surfaces and subsurface deformation have been carried out. The wear mechanism was studied through worn surfaces and microscopic examination of the developed wear tracks. The wear mechanism strongly dictated by the formation and stability of oxide layer, mechanically mixed layer (MML) and subsurface deformation and cracking. The overall results indicate that the aluminium alloy–silicon carbide particle composite could be considered as an excellent material where high strength and wear resistance are of prime importance.     

Dry sliding wear behaviour of PTFE filled with glass and bronze particles

Abstract

The wear behaviour of polytetrafluroethylene (PTFE) filled with 25% glass and 40% bronze particles was studied on a pin on disc test rig. Solid lubricant composite materials were prepared by compression moulding technique. The wear parameters considered for the study were applied load, sliding speed and sliding distance. The experimental results indicate that the weight loss increases with increasing load, sliding speed and sliding distance, as expected. Sliding distance has more effect on weight loss followed by applied load. The 40% bronze+PTFE composite exhibits better wear resistance compared to other types. The dominant interactive wear mechanisms during sliding of PTFE and its composites are discussed in this paper.     

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.     

Wear study of Ni–WC composite coating modified with CeO2

In the present investigation, Ni–WC composite powder was modified with the addition of CeO₂ in order to form a new composition of Ni–WC–CeO₂. The Ni–WC and Ni–WC–CeO₂ compositions were used for coating deposition by high-velocity oxy-fuel (HVOF) spraying process so as to study the effect of CeO₂ addition on microstructure, distribution of various elements, hardness, formation of new phases, and abrasive wear behavior. Further, the effect of load, abrasive size, sliding distance, and temperature on abrasive wear behavior of these HVOF-sprayed coatings was investigated by response surface methodology. To investigate the abrasive wear behavior of HVOF-sprayed coatings four factors such as load, abrasive size (size in micrometers), sliding distance (meters), and temperature (°C) with three levels of each factor were investigated. Analysis of variance was carried out to determine the significant factors and interactions. Investigation showed that the load, abrasive size, and sliding distance were the main significant factors while load and abrasive size, load and sliding distance, abrasive size and sliding distance were the main significant interactions. Thus an abrasive wear model was developed in terms of main factors and their significant interactions. The validity of the model was evaluated by conducting experiments under different wear conditions. A comparison of modeled and experimental results showed 4–9% error. The abrasive wear resistance of coatings increases with the addition of CeO₂. This is due to increase in hardness with the addition of CeO₂ in Ni–WC coatings.     

Tribological properties of Ni3Al-Cr7C3 composite coating under water lubrication

The tribological properties of Ni₃Al-Cr₇C₃ composite coating under water lubrication were examined by using a ball-on-disc reciprocating tribotester. The effects of load and sliding speed on wear rate of the coating were investigated. The worn surface of the coating was analyzed using electron probe microscopy analysis (EPMA) and X-ray photoelectron spectroscopy (XPS). The results show the friction coefficient of the coating is decreased under water lubrication. The wear rate of the coating linearly increases with the load. At high sliding speed, the wear rate of the coating is dramatically increased and a large amount of the counterpart material is transferred to the coating worn surface. The low friction of the coating under water lubrication is due to the oxidizing of the worn surface in the wear. The wear mechanism of the coating is plastic deformation at low normal load and sliding speed. However, the wear mechanism transforms to microfracture and microploughing at high load with low sliding speed, and oxidation wear at high sliding speed. It is concluded that the contribution of the sliding speed to an increase in the coating wear is larger than that of the normal load.     

Sliding wear behavior of Fe-Al and Fe-Al/WC coatings prepared by high velocity arc spraying

A comparative study was carried out to investigate the microstructure and tribological behavior of Fe-Al and Fe-Al/WC iron aluminide based coatings against Si₃N₄ under dry sliding at room temperature using a pin-on-disc tribotester. The coatings were prepared by high velocity arc spraying (HVAS) and cored wires. The effect of normal load on friction coefficient and wear rate of the coatings was studied. The microstructure and the worn surfaces of the coatings were analysed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersion spectroscope (EDS). The results showed that, the main phases in both coatings were iron aluminide (Fe₃Al and FeAl) and α. WC/W₂C particles were embedded in the matrix of the composite coating. With adding WC hard particles, the Fe-Al/WC composite coating exhibited higher wear-resistance than Fe-Al coating. But the friction coefficient of both coatings showed little difference. As the load increased, the friction coefficient decreases slightly due to a rise of friction contact temperature and larger areas of oxide film formation on the worn surface, which act as a solid lubricant. Increasing load causes the maximum shear stress occurring at the deeper position below the surface, thereby aggravating the wear. The coating surface is subjected to alternately tensile stress and compression stress during sliding, and the predominant wear mechanism of the coatings appears to be delamination.     

Friction and wear behavior of Ni-P coated Si3N4 reinforced Al6061 composites

Al6061 matrix composite reinforced with nickel coated silicon nitride particles were manufactured by liquid metallurgy route. Microstructure and tribological properties of both matrix alloy and developed composites have been evaluated. Dry sliding friction and wear tests were carried out using pin on disk type machine over a load range of 20-100 N and sliding velocities of range 0.31-1.57 m/s. Results revealed that, nickel coated silicon nitride particles are uniformly distributed through out the matrix alloy. Al6061-Ni-P-Si₃N₄ composite exhibited lower coefficient of friction and wear rate compared to matrix alloy. The coefficient of friction of both matrix alloy and developed composite decreased with increase in load up to 80 N. Beyond this, with further increase in the load, the coefficient of friction increased slightly. However, with increase in sliding velocity coefficient of friction of both matrix alloy and developed composite increases continuously. Wear rates of both matrix alloy and developed composites increased with increase in both load and sliding velocity. Worn surfaces and wear debris was examined using scanning electron microscopy (SEM) for possible wear mechanisms. Energy dispersive spectroscope (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscope (XPS) techniques were used to identify the oxides formed on the worn surfaces and wear debris.     

The effect of an alumina counterface on friction reduction of CuO/3Y-TZP composite at room temperature

The friction behavior of CuO/yttria-stabilized tetragonal zirconia (3Y-TZP) composite in dry sliding against alumina at room temperature has been investigated. The results show that an alumina counterface has a crucial role on the frictional behavior when sliding against CuO/3Y-TZP composite in comparison with other counter materials. Pure 3Y-TZP shows high friction and wear under the same conditions. It is found that the friction reduction behavior is dependent on the sliding test conditions such as load and humidity. A thin aluminum-rich layer less than 200 nm thick on the contact surface during the low friction situation has been found by various analyzing techniques including interference microscopy, micro-Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microcopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The induced change of contact conditions and interfacial chemical reaction between CuO and alumina to form the phase CuAlO₂ increase the wear of alumina and accelerates the formation of an aluminum-rich surface layer. The presence of such a layer in the contact is beneficial for reducing friction. After a certain sliding distance, the coefficient of friction shifts from a low value to a high value due to a change in the dominating wear mechanism. This transition is shown to be caused by a different composition and thickness of the interfacial layer.     

Adhesive wear and frictional characteristics of UHMWPE and HDPE sliding against different counterfaces under dry contact condition

Abstract

The current work evaluates the wear and frictional performance of ultrahigh molecular weight polyethylene (UHMWPE) and high density polyethylene (HDPE) sliding against different metal counterfaces, stainless steel(SS), mild steel (MS) and aluminium (Al), under dry contact condition. The experiments were conducted using pin on disc machine at different sliding distances (0–40·32 km), 15 N applied load and 2·8 m s^–1 sliding velocity. Interface temperatures and frictional forces were measured simultaneously during the sliding, while specific wear rates were determined for every 1·68 km sliding distance. Based on the optical microscopy of the worn surface and wear track, frictional and wear results were analysed and discussed. The experimental results showed that the type of counterface material significantly influences both frictional and wear performances of the selected polymers. This was mainly due to the film transfer characteristics. Higher temperature and friction coefficient for UHMWPE and HDPE were evident when sliding took place against Al counterface. Sliding the polymers against stainless steel showed low friction coefficients compared to other counterfaces.     

Rippling on Wear Scar Surfaces of Nanocrystalline Diamond Films After Reciprocating Sliding Against Ceramic Balls

The formation of nanoscopic ripple patterns on top of material surfaces has been reported for different materials and processes, such as sliding against polymers, high-force scanning in atomic force microscopy (AFM), and surface treatment by ion beam sputtering. In this work, we show that such periodic ripples can also be obtained in prolonged reciprocating sliding against nanocrystalline diamond (NCD) films. NCD films with a thickness of 0.8 µm were grown on top of silicon wafer substrates by hot-filament chemical vapor deposition using a mixture of methane and hydrogen. The chemical structure, surface morphology, and surface wear were characterized by Raman spectroscopy, scanning electron microscopy (SEM), and AFM. The tribological properties of the NCD films were evaluated by reciprocating sliding tests against Al₂O₃, Si₃N₄, and ZrO₂ counter balls. Independent of the counter body material, clear ripple patterns with typical heights of about 30 nm induced during the sliding test are observed by means of AFM and SEM on the NCD wear scar surfaces. Although the underlying mechanisms of ripple formation are not yet fully understood, these surface corrugations could be attributed to the different wear phenomena, including a stress-induced micro-fracture and plastic deformation, a surface smoothening, and a surface rehybridization from diamond bonding to an sp ² configuration. The similarity between ripples observed in the present study and ripples reported after repeated AFM tip scanning indicates that ripple formation is a rather universal phenomenon occurring in moving tribological contacts of different materials.     

Application of grey-taguchi method for optimization of dry sliding wear properties of aluminum MMCs

Through a pin-on-disc type wear setup, the dry sliding wear behavior of SiC-reinforced aluminum composites produced using the molten metal mixing method was investigated in this paper. Dry sliding wear tests were carried on SiC-reinforced metal matrix composites (MMCs) and its matrix alloy sliding against a steel counter face. Different contact stresses, reinforcement percentages, sliding distances, and sliding velocities were selected as the control variables, and the responses were selected as the wear volume loss (WVL) and coefficient of friction (COF) to evaluate the dry sliding performance. An L25 orthogonal array was employed for the experimental design. Initially, the optimization of the dry sliding performance of the SiC-reinforced MMCs was performed using grey relational analysis (GRA). Based on the GRA, the optimum level parameters for overall grey relational grade in terms of WVL and COF were identified. Analysis of variance was performed to determine the effect of individual factors on the overall grey relational grade. The results indicated that the sliding velocity was the most effective factor among the control parameters on dry sliding wear, followed by the reinforcement percentage, sliding distance, and contact stress. Finally, the wear surface morphology and wear mechanism of the composites were investigated through scanning electron microscopy.     

The influence of alumina on mechanical and tribological characteristics of graphite particle reinforced hybrid Al-MMC

We consider the influence of alumina (Al₂O₃) particles on mechanical and tribological properties of aluminum hybrid metal matrix composites (MMC). Various weight fraction of Al₂O₃ (5, 10 and 15%) and constant weight fraction of graphite (5%) were used to fabricate composites by stir casting method. The effect of Al₂O₃ content on hardness, density and specific wear rate is evaluated. A wear test was performed using central composite design matrix on a pin-on disc apparatus at room temperature for constant sliding distance of 1000 m. The sliding speed, load and weight fraction of Al₂O₃ were the process variables. The results show that the hardness and density increase with increase in Al₂O₃ content. From the analysis of variance (ANOVA), load is the dominant factor that affects the specific wear rate of hybrid composites followed by speed and weight fraction of Al₂O₃. Based on desirability approach, the improvement in the wear resistance of the composites became more prominent at high speed, high load and high weight fraction of Al₂O₃. The worn surface of the pin was examined using scanning electron microscope (SEM) which indicates that the wear mechanism of composites is mostly abrasive wear followed by oxide wear.     

Parametric study of the dry sliding wear behaviour of AA6082-T6/SiC and AA6082-T6/B<Subscript>4</Subscript>C composites using RSM

In this paper a parametric study of the wear behaviour of Aluminum matrix composites has been carried out. AA6082-T6/SiC and AA6082-T6/B₄C composites were fabricated using stir casting technique. The percentage of reinforcement was taken as 5, 10, 15 and 20 wt.% for both SiC and B₄C particulates. Dry sliding wear tests were conducted using pin-on-disc apparatus at room temperature and process optimization was done using Response surface methodology (RSM). Weight percentage (wt.%) of reinforcement, sliding speed, load and sliding distance were the four process parameters considered to analyse these composites wear behaviour. Analysis of variance (ANOVA) showed that sliding distance exerted the highest contribution (60.24 %) to AA6082-T6/SiC wear, followed by sliding speed (14.28 %), load (11.88 %) and reinforcement content (4.31 %). The same trend was found in AA6082-T6/B₄C composites with slightly different contribution values, namely sliding distance (63.28 %), sliding speed (14.02 %), load (10.10 %) and reinforcement content (4.05 %). RSM analysis revealed that increases in the reinforcement content and sliding speed reduce the wear rate in both composites. On the other hand, increases in load and sliding distance led to higher AA6082-T6/SiC and AA6082-T6/B₄C composites wear. The two predictive models were validated by conducting confirmation tests and certified that the developed wear predictive models are accurate and can be used as predictive tools for wear apllications.     

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.     

An investigation on worn surfaces of chopped glass fibre reinforced polyester through SEM observations

The wear mechanisms of chopped strand mat (CSM) glass fibre reinforced polyester (CGRP) composite subjected to dry sliding against smooth stainless steel counterface (R_a=0.06 μm) were studied using a pin-on-disc technique. The effects of normal load (30-90 N), sliding velocity (2.8-3.9 m/s) and sliding distance (0.7-3.5 km) on friction and wear behaviour of the CGRP composite in two different CSM orientations (parallel and anti-parallel) were measured. The worn surfaces of the CGRP composite specimens for each specific test condition were examined using scanning electron microscopy (SEM).Sliding in P-orientation exhibited lower friction coefficient at lower load and higher speed compared to AP-orientation. Meanwhile, sliding in AP-orientation exhibited (15%) less friction coefficient at higher load compared to P-orientation. At higher range of all tested parameters, AP-orientation exhibited less mass loss (16%) compared to the P-orientation.Interestingly, SEM observations showed various wear mechanisms that predominated by abrasive nature. Damage of different features in the matrix and CSM glass fibre associated with higher values of load, speed, and sliding distance such as micro- and macro-cracks in the matrix, interface separation, fibre debonding and fracture, and different sizes of fractured fibres were evident.