Sliding wear behaviour of aluminum syntactic foam: A comparison with Al-10 wt% SiC composites

The sliding wear behaviour of cenosphere-filled aluminum syntactic foam (ASF) has been studied in comparison with that of 10 wt% SiC particle reinforced aluminum matrix composite (AMC) at a load of 3 kg and varying sliding speeds under dry and lubricated conditions using a pin-on disc test apparatus. The tribological responses such as the wear rate, the coefficient of friction and the frictional heating were investigated. The wear surfaces and subsurfaces were studied for understanding the wear mechanism. It was noted that the coefficient of friction, the wear rate, and the temperature rise for ASF are less than that for AMC in both dry and lubricated conditions. The craters (vis-à-vis exposed cenospheres) play an important role in the wear mechanism for ASF.     

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.     

On dry sliding friction and wear behaviour of PEEK and PEEK/SiC-composite coatings

In this work, polyetheretherketone (PEEK) and PEEK/SiC-composite coatings were deposited on Al substrates using a printing technique to improve their surfaces performance. The objective of this work was to investigate coatings friction and wear behaviour. Especially, the effect of sliding velocity and applied load on coatings friction coefficient and wear rate was evaluated in range of 0.2-1.4 m/s and 1-9 N, respectively. Compared to Al substrate, the coated samples exhibit excellent friction coefficient and wear rate. For PEEK coating, under an applied load of 1 N, the increase in sliding velocity can result in decreasing of friction coefficient at a cost of wear resistance. Under a load of 9 N, however, PEEK coating exhibits the highest friction coefficient and wear rate at an intermediate velocity. These influences appear to be mainly ascribed to the influence of contact temperature of the two relative sliding parts. In most test conditions, the composite coating exhibits better wear resistance and a little higher friction coefficient. SiC reinforcement in composite coating plays a combined role. First of all, it might lead to energy dissipation for activation of fracture occurred on the interface of PEEK and the powders. Moreover, it can reduce coating ploughs and the adhesion between the two relative sliding parts.     

Wear and friction behavior of sand cast brake rotor made of A359-20 vol% SiC particle composites sliding against automobile friction material

The effect of load range of 30-100 N and speed range of 3-12 m/s on the wear and friction behavior of sand cast brake rotor made of A359-20 vol% SiC particle composites sliding against automobile friction material was investigated. Dry sliding frictional and wear behavior were investigated in a pin-on-disc type apparatus. Automobile friction material was used as pin, while the A359-20 vol% SiC particle composites formed the rotating disc. For comparison, the wear and friction behavior of commercially used cast iron brake rotor were studied. The results showed that the wear rate of the composite disc decreased with increasing the applied load from 30 to 50 N and increased with increasing the load from 50 to100 N. However, the wear rate of the composite disc decreased with increasing the sliding speed at all levels of load applied in the present work. For all sliding speeds, the friction coefficient of the composite disc decreased with applied load. The worn surfaces as well as wear debris were studied using scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analyzer and X-ray diffraction (XRD) technique. At load of 50 N and speed range of 3-12 m/s, the worn surface of the composite disc showed a dark adherent layer, which mostly consisted of constituents of the friction material. This layer acted as a protective coating and lubricant, resulting in an improvement in the wear resistance of the composite.     

Sliding wear behavior of planar random zinc-alloy matrix composites

The friction and wear behavior of planar random zinc-alloy matrix composites reinforced by discontinuous carbon fibres under dry sliding and lubricated sliding conditions has been investigated using a block-on-ring apparatus. The effects of fibre volume fractions and loads on the sliding wear resistance of the zinc-alloy matrix composites were studied. Experiments were performed within a load range of 50–300 N at a constant sliding velocity of 0.8 m s⁻¹. The composites with different volume fractions of carbon fibres (0–30%) were used as the block specimens, and a medium-carbon steel used as the ring specimen. Increasing the carbon fibre volume fraction significantly decreased the coefficient of friction and wear rates of both the composites and the medium-carbon steel under dry sliding conditions. Under lubricated sliding conditions, however, increasing the carbon fibre volume fraction substantially increased the coefficient of friction, and slightly increased the wear of the medium-carbon steel, while reducing the wear of the composite.Under dry sliding conditions, an increasing load increased not only the wear rates of both the composite and the unreinforced zinc alloy, but also those of their corresponding steel rings. However, the rate of increase of wear with increasing load for both the composite and its corresponding steel ring was much smaller than for the unreinforced zinc alloy and its corresponding steel ring. The coefficient of friction under dry sliding conditions appeared to be constant as load increased within a load range of 50–150 N for both the composite and the unreinforced zinc alloy, but increased at the higher loads. Under any load the coefficient of friction of the composite was lower than half that of the unreinforced zinc alloy under dry sliding conditions.     

Corrosion and wear of 6082 aluminum alloy

The corrosion and corrosive wear resistance of 6082 wrought aluminum alloy against 410 stainless steel counterface in 0.01 M NaCl solution with different concentrations of sodium molybdate dihydrate solution (0, 0.01, 0.1 and 0.5 M), were studied. The experimental results indicated that the increase in sodium molybdate dihydrate acted as an inhibitor in the 0.01 M NaCl solution resulting in a significant decrease in the corrosion current, meaning improved corrosion resistance. During the corrosive wear under free corrosion conditions of 6082 aluminum alloy specimens against 410 stainless steel counterface, the addition of sodium molybdate dihydrate inhibitor, leads to a decrease in friction coefficient of the examined pair of materials. The dominant wear mechanisms of the aluminum alloy were mainly observed to be plastic deformation and abrasion. These wear mechanisms coexisted with pitting corrosion phenomena, on the surface of this alloy.     

Surface morphology in engineering applications: Influence of roughness on sliding and wear in dry fretting

Influence of initial surface roughness on friction and wear processes under fretting conditions was investigated experimentally. Rough surfaces (Ra=0.15-2.52 μm) were prepared on two materials: carbon alloy (AISI 1034) and titanium alloy (Ti-6Al-4V). Strong influence of initial surface roughness on friction and wear processes is reported for both tested materials. Lower coefficient of friction and increase in wear rate was observed for rough surfaces. Wear activation energy is increasing for smoother surfaces. Lower initial roughness of surface subjected to gross slip fretting can delay activation of wear process and reduce wear rate; however, it can slightly increase the coefficient of friction.     

Wear and friction behavior of Al6061 alloy reinforced with carbon nanotubes

Friction and wear behavior of Al6061 monolithic alloy and 1 wt% CNTs reinforced Al6061 composite prepared through ball milling and spark plasma sintering was investigated. It was found that, under mild wear conditions, the composite displayed lower wear rate and friction coefficient compared to the monolithic alloy. However, for severe wear conditions, the composite displayed higher wear rate and friction coefficient compared to the monolithic alloy. Analysis of worn surfaces revealed that, at lower loads, abrasion was the dominant wear mechanism for both materials. At higher loads, adhesion was found to be dominant for the monolithic alloy while excessive sub-surface fracturing and delamination were mainly observed for the composite. Also, it was clarified that the friction and wear behavior of Al–CNT composites is largely influenced by the applied load and there exists a critical load beyond which CNTs could have a negative impact on the wear resistance of aluminum alloy.     

Friction and wear properties of Babbitt alloy 16-16-2 under sea water environment

The tribological behaviors of Babbitt alloy 16-16-2 sliding against aluminum bronze ZCuAl9Mn2 lubricated by sea water were systematically investigated in this paper. The results indicated that the friction coefficient decreased as the load increased to 30 N and then remained at a steady level at high loads, but decreased with increase in sliding speed. The wear rate increased with load, but decreased with sliding speed. The formation of basic lead carbonate Pb₃(OH)₂(CO₃)₂ during the sliding process played a critical role in the remaining low friction coefficient in sea water.     

Transfer Solid Lubrication of Aluminum Sliding Contacts

The effects of transfer from solid lubricant sticks of unfilled, glass-filled, and bronze-filled PTFE on the room-temperature wear and friction of trailing primary contacts of aluminum (6061 T6) rods in repetitive intermittent contacts were investigated in a ring-on-rod configuration. The materials of the ring countersurfaces upon which the solid lubricants transferred and against which the trailing aluminum rods wore included steel, aluminum, copper, and an oxide dispersion-strengthened copper alloy. This sliding of the unlubricated copper ring countersurfaces against the aluminum led to the roughening of the copper as large (> 1 mm) aluminum particles embedded themselves upon the countersurface, with consequent transitions in the aluminum wear rate and the coefficient of friction to values exceeding 6 × 10^{? 3} mm³/Nm and 0.6, respectively, after an incubation period of several initial contacts of lower wear rate and friction. The other ring countersurface materials resulted in similarly high aluminum rod wear rate and coefficient of friction, more nearly from the onset of sliding. The application of unfilled PTFE solid lubricant transfer reduced the aluminum's gouging of the copper countersurfaces and correspondingly reduced the aluminum rod wear rate and the coefficient of friction against the copper, as well as against all other countersurface materials, towards 2 × 10^?3 mm³/Nm and 0.3 or less, respectively. Glass- and bronze-filled PTFE transfer lubricants provided reductions in the wear rate of the aluminum rod comparable to or in some cases better than the unfilled PTFE, though the unfilled PTFE transfer lubricant in several cases provided better friction reduction.     

压渗法制备陶瓷网络复合材料摩擦行为研究

提出了三维陶瓷网络(骨架)增强金属基复合材料的新构思,设计和制备了一种新型的三维陶瓷网络(骨架)增强铝合金复合材料,研究了其在干摩擦状态下的滑动摩擦磨损行为。结果表明,基体铝合金在重载时产生严重粘着磨损,磨损层发生软化和塑性流动,而复合材料中的陶瓷颗粒暴露于磨损表面并起承载作用,从而保护基体小发生严重磨损。与基体合金相比,复合材料摩擦因数平稳而较低,且耐磨性提高6倍左右。     

Friction and wear behavior of electroless Ni-based CNT composite coatings

Ni-based carbon nanotube (CNT) composite coatings with different volume fraction (from 5 to 12 vol.%) of CNTs were deposited on medium carbon steel substrates by electroless plating. The friction and wear behavior of the composite coatings were investigated using a pin-on-disk wear tester under unlubricated condition. Friction and wear tests were conducted at a sliding speed of 0.0623 m s⁻¹ and at an applied load of 20 N. The experimental results indicated that the friction coefficient of the composite coatings decreased with increasing the volume fraction of CNTs due to self-lubrication and unique topological structure of CNTs. Within the range of volume fraction of CNTs from 0 to 11.2%, the wear rate of the composite coatings showed a steadily decreasing trend with increasing volume fraction of CNTs. Because of the conglomeration of CNTs in the matrix, however, the wear rate of the composite coatings increased with further increasing the volume fraction of CNTs.     

Dry sliding friction and wear properties of Al-25Zn-3Cu-3Si alloy

Friction and wear properties of Al-25Zn-3Cu-3Si alloy were investigated over a range of pressure and sliding speed using a pin-on-disc test machine. The friction coefficient of the alloy increased with sliding speed, but decreased with increasing pressure up to 1.5 MPa, above which the trend reversed. However, the temperature and wear volume of the alloy increased continuously with increasing pressure and sliding speed. A fine-grained layer and a region with flow lines were observed underneath the surface of the wear samples. The formation of these regions was related to smearing of wear particles and heavy deformation of surface material, respectively.     

Tribocorrosion behavior of Ni-17.5Si-29.3Cr alloy in sulfuric acid solution

The tribocorrosion property of a Ni-17.5Si-29.3Cr alloy against a Si₃N₄ ball was studied in comparison with AISI321 stainless steel using a ball-on-disk reciprocating tribotester in 1 M sulfuric acid (H₂SO₄) solution. The effects of load and sliding speed on the tribocorrosion properties of the alloy were investigated. The results indicated that the wear rate of the alloy increased while the friction coefficient decreased with increasing load. The wear rate of the alloy increased linearly with increasing sliding speed and the friction coefficient increased in the initial stages and then remained constant with increasing sliding speed. The wear mechanisms were mainly microploughing, uniform corrosion and pitting corrosion. Under the experimental conditions of the present study, the Ni-17.5Si-29.3Cr alloy showed excellent corrosion-resistence and anti-wear ability compared with AISI321 stainless steel.     

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.     

Enhancement of abrasive wear resistance in consolidated Al matrix composites via extrusion process

Abstract

The present study addresses the dry wear behaviour of aluminium matrix composites under different sliding speeds and applied loads. Values of the friction coefficient of the matrix alloy and composite materials were in expected range for light metals in dry sliding conditions. The higher coefficient of friction was the consequence of established contact between hard SiC particles and the counter body material. The rough and smooth regions are distinguished on the worn surface of the composites similar to the unreinforced Al alloy. Plastic deformation occurred when the applied specific load was higher than the critical value. The high shear stresses on the sliding surface cause initiation and propagation of the cracks in the subsurface, leading to the loss of material from the worn surface in the form of flakes. The debrises of the composites at low wear rate comprise a mixture of the fine particles and small shiny metallic plate-like flakes and are associated with the formation of more iron rich layers on the contact surfaces.     

Tribological performance evaluation of (1 1 1) preferred oriented TiN duplex coatings

The duplex surface coating of hot work tool steel, which comprises nitriding of a substrate and coating of a TiN layer, has been the subject of a series of studies as a potential surface modification for tools and machine parts. Through sliding experiment against an aluminum alloy without lubrication, it was shown on a wear map that there are two domains depending on sliding conditions: the wear domain and the transfer domain. In this study, focusing on the improvement in the tribological properties of the duplex coating in terms of the wear domain, the effects of film characteristics on film resistance to erosion wear and film life were investigated. Two kinds of duplex coatings with different film characteristics were prepared by hollow cathode discharge ion plating: a newly developed TiN film with a strong (1 1 1) orientation and an ordinary TiN film with (1 1 1) and (2 0 0) orientations. The erosion wear rate of duplex coating was evaluated by a micro slurry jet erosion test. Film life was evaluated by a sliding test against an aluminum alloy as in previous experiments. It was revealed that the duplex coating with the newly developed TiN film (N-coating) shows higher erosion resistance than previously reported duplex coating (C-coating). From the sliding test, it was also revealed that the N-coating whose XRD intensity ratio of (1 1 1) to (2 0 0) is over 100 shows a wear mode with only chipping, with no scratching, which shortens film life. The film life of N-coating increases about twice as long as C-coating, which has shown higher performance than a conventional duplex coating. Possible mechanisms of the improvement in the tribological properties with N-coating are discussed.     

Dry sliding wear of fly ash particle reinforced A356 Al composites

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

Effect of heat treatment on the sliding wear behaviour of aluminium alloy (Al–Zn–Mg) hard particle composite

Effect of heat treatment on the sliding wear behaviour of aluminium alloy hard particle composite was studied under varying applied load and sliding speed, giving emphasis on the parameters such as wear rate, temperature rise, coefficient of friction and seizure pressure. Hardness is improved due to heat treatment irrespective of the material. Maximum hardness is noted when the materials are aged for 6 h. These facts have been discussed on the basis of nature of worn surface produced after wear. In the present investigation, aging time has been varied from 4 to 10 h at a regular increment of 2 h.     

Friction and wear behaviour of stainless steel rubbing against copper-impregnated metallized carbon

A series of experimental tests were carried out using stainless steel rubbing against copper-impregnated metallized carbon under electrical current on a pin-on-disc test rig. The test parameters include the sliding speed of 60-100 km/h, normal force of 40-80 N and electrical current of 0-50 A. During testing, the friction coefficient and wear volume were recorded. The topography of worn surfaces was also observed with SEM. The cross sectional profiles of worn surfaces of stainless steel were measured with Ambios profiler. The result displays that electrical current, normal load and sliding speed have a distinct effect on the friction and wear behaviour of stainless steel rubbing against copper-impregnated metallized carbon. Without electric current, the friction coefficient is largest but the wear volume of copper-impregnated metallized carbon is lowest. With increasing electric current, the friction coefficient decreases while the wear volume of copper-impregnated metallized carbon increases. Through the whole test, it is found that the wear loss of stainless steel was light. The wear of copper-impregnated metallized carbon becomes severe when electrical current or sliding speed is high. When the electrical current or sliding speed is high, arc ablation is a dominant wear mechanism of copper-impregnated metallized carbon.