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.     

Tribological behaviour of PTFE modified cotton polyester composites

Abstract

An attempt on modification of tribological behaviour of cotton polyester composite was done with polytetrafluoroethylene (PTFE). PTFE modified polyester–cotton composites were developed and studied for their friction and sliding wear behaviour at different applied loads. The sliding wear tests of composites were conducted against EN-31 steel counter face. The coefficient of friction μ as well as the sliding wear rate of cotton–polyester composites reduced significantly on addition of PTFE. The reduction in wear rate of PTFE modified polyester–cotton composite has been discussed with the help of SEM observations of worn surfaces and coefficient of friction.     

A study on tribological behaviour of transfer films of PTFE/bronze composites

Transfer films of PTFE/bronze composites with 5–30% volume content of bronze were prepared using a RFT friction and wear tester on surface of AISI-1045 steel bar by different sliding time (5–60 min). Tribological properties of these transfer films were studied using a DFPM reciprocating tribometer in a point contacting configuration under normal loads of 0.5, 1.0, 2.0 and 3.0 N. Thickness and surface morphology of the transfer films were investigated. It was found thickness of the transfer films slightly increased along with the increase of bronze content of corresponding composites. Increased sliding time of transfer film preparation is helpful to form transfer film with better ductibility and continuity, but sliding time almost has no effect on tribological properties of the transfer film. Higher bronze content in the composite improved tribological properties of the corresponding transfer film, i.e., reduced friction coefficient and prolonged wear life. All these transfer films are sensitive to load change. Their wear life becomes shorter along with the increase of load. SEM image of the worn surface show fatigue wear and adhesion wear have happened on the transfer film during the friction process. The author believe bronze in the transfer film effectively partaked in shear force applied on the transfer film and its good ductibility helped to improve tribological properties of the transfer films.     

Effect of load and speed on the wear behaviour of woven glass fabrics and aramid fibre-reinforced composites

In the present study, wear behaviour of woven 300 and 500 glass fabrics and aramid fibre-reinforced composite materials are experimentally investigated for 500 and 710 rpm speeds and at two different loads of 500 and 1000 g using a block-on-shaft wear tester. The wear in the experiments was determined as weight loss. The weight losses were measured after different sliding distance conditions. The worn surfaces were also examined by scanning electron microscope (SEM). As a result of this study, it is shown that the applied load on the specimens has more effect on the wear than the speed. Also the weight loss in the woven 500 glass fabric reinforced is more than that in the woven 300 glass fabric-reinforced composite. The weight loss of aramid fibre-reinforced composite is quite low compared with woven glass fabric-reinforced composites.     

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.     

Synergetic Effect of Lubricant Additive and Reinforcement Additive on the Tribological Behaviors of PEEK-Based Composites under Seawater Lubrication

Polyetheretherketone (PEEK)-based composites reinforced with lubricant additive (polytetrafluoroethylene, PTFE) and reinforcement additives including carbon fiber (CF), glass fiber (GF), and bronze powder were prepared using a hot-press molding technique. The synergetic effects of different additives on the tribological behaviors of PEEK-based composites sliding against 316 steel under seawater lubrication were investigated systematically using a ring-on-block test rig. The results showed that lubricant additive PTFE can decrease the friction coefficient and consequently improved the wear resistance of PEEK under seawater lubrication, especially when the volume fraction of PTFE was about 20%. It was also found that the incorporation of CF can further improve the wear resistance of PEEK blended with 20% PTFE, especially under high load and high sliding speed. This suggested that a synergistic effect on improving the wear resistance of PEEK existed between PTFE and CF, which originated from good lubrication of PTFE, good reinforcement of CF, and good interfacial combination between CF and PEEK-20%PTFE. However, two other reinforcement additives of GF and bronze powder had an antagonistic effect but not a synergetic effect with PTFE; that is, the incorporation of the two additives greatly deteriorated the wear resistance of PEEK blended with 20% PTFE.     

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.     

Friction and wear behavior of self-lubricating and heavily loaded metal–PTFE composites

A new 16 MnNb steel–PTFE composite (A) containing 60% area proportion of PTFE composite was developed. Another type of common solid lubricant embedded C86300 bronze–PTFE composite (B) containing 35% area proportion of PTFE composite was also selected for a comparative investigation under similar testing conditions. Friction and wear experiments were performed in an oscillating sliding tribotester at an oscillating frequency of 0.13 Hz, contact mean pressures from 15 to 80 MPa and counterface roughness of 0.10 μm R_a. The composites A and B slid against a 38CrMoAlA steel shaft. Results showed that the composite A exhibited low coefficient of dry friction and long wear life as compared to that of the composite B. It was found that the surface of PTFE composite was higher than that of steel backing at the intervals of testing. This was because modulus of the elasticity of PTFE composite was much lower than that of 16 MnNb steel backing; under a same load condition the elastic deformation amount of PTFE composite was much bigger than that of steel backing. Thus, the composite A provided sufficient lubrication during the whole tests.     

Dry reciprocating wear of Al-Si-SiCp composites: A statistical analysis

In this paper, effect of various wear test and material related parameters (applied load, sliding distance, reciprocating velocity, counter surface temperature and weight percentage of silicon) on dry wear behavior of two Al-Si-SiC_p composites under reciprocating conditions was studied using fractional factorial design. Developed mathematical model showed that Al-Si-SiC_p with high silicon content composite is subjected to a lower wear compared to that of low silicon composite. The applied load, sliding distance, reciprocating velocity and percentage silicon weight in composite are the four important and controlling factors; counter surface temperature has a minor effect on the wear of the composite specimens in dry condition.     

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.     

纳米SiO2颗粒和玻璃微珠共混改性超高分子量聚乙烯复合材料的摩擦磨损性能

采用模压成型工艺制备了纳米SiO2颗粒和玻璃微珠共混改性的超高分子量聚乙烯复合材料;研究了相对滑动速度、载荷以及玻璃微珠含量对复合材料摩擦磨损性能的影响,并对磨损形貌和磨损机理进行了分析。结果表明:添加纳米SiO2颗粒和玻璃微珠可以提高复合材料的硬度、压缩弹性模量和摩擦磨损性能;相对滑动速度对复合材料摩擦因数和磨损率有很大的影响;载荷对复合材料的摩擦因数影响不明显,但磨损率随载荷的增加而增大;纳米SiO2颗粒和玻璃微珠混合改性后复合材料的磨损机理主要是粘着磨损和疲劳磨损。     

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.     

Analysis of Tribological Performance of Cu Hybrid Composites Reinforced with Graphite and TiC Using Factorial Techniques

In this study, a copper hybrid metal matrix composite reinforced with graphite (5, 10, and 15 vol%) and TiC (5, 10, and 15 vol%) was processed by a powder metallurgy route. Optical micrographs confirm the uniform distribution of reinforcements in the copper matrix. The hardness of the composites decreased with the addition of graphite. However, the addition of TiC into the copper matrix increased the hardness of the composites due to its high hardness. The influence of graphite percentages, load, sliding speed, and sliding distance on the wear of the as-sintered hybrid composites was studied based on the design of experiments. Analysis of variance (ANOVA) was used to study the effect of the parameters on the wear weight loss of the hybrid composites. The weight loss due to wear of the hybrid composites decreases from 0.1345 to 0.0830 g as the volume percentage of graphite increases from 5 to 15%. Results indicated that the normal load has greater static influence of 43.85%, sliding distance has an influence of 29.84%, percentage of graphite has an influence of 15.17%, and sliding speed has an influence of 1.83% on the weight loss of copper hybrid composites due to sliding wear. The worn-out surfaces were analyzed using electron microscopy, which reveals that the addition of both hard ceramic reinforcement TiC and soft solid lubricant graphite significantly improves the tribological performance of the copper composites.     

Two body dry abrasive wear of TiC–NiMo cermets

Abstract

The present paper covers the two body dry abrasive wear of a series of titanium carbide base cermets with different amounts of NiMo binder phases (20–60 wt-%) using a 'block on abrasive grinding wheel' test machine. The wear coefficient of the cermets decreases with increasing TiC and Mo contents in the composite, which corresponds to an increase in bulk hardness. The volume loss increases with the increases in the sliding distance and the applied normal load, as predicted by the Rabinowitcz equation. The post-run wear tracks of the worn blocks were analysed by SEM to determine the wear mechanisms. The material is actually removed by several processes which scale the process of groove formation, including the formation of subsurface cracks by a fatigue process under repeated abrasion.     

Wear behaviour of AE42+20% saffil Mg-MMC

The wear behaviour of AE42 magnesium alloy and AE42+20% saffil short fibre composite is investigated in dry sliding condition using a pin-on-disc set-up in the load range of 5–40 N with sliding speeds of 0.838, 1.676 and 2.513 m/s for a constant sliding distance of 2.5 km. In case of both the alloy and the composite wear rate increases with increasing loads and the wear rate of the composite is lower at lower loads. At all sliding speeds, a crossover in wear rate is observed with the increase in load, i.e., above a certain load the wear rate of the composite becomes greater than that of the alloy, and the crossover shifts to lower loads with increase in the sliding speed. Severe sub-surface plastic deformation and fibre breakage are found to be the dominant mechanism for the unreinforced alloy and the composite, respectively.     

Tribological Behavior of Aluminum Hybrid Composites Studied by Application of Factorial Techniques

This article analyzes the influence of graphite reinforcement, load, sliding speed, and sliding distance on tribological behavior of A356 aluminum matrix composites reinforced with silicon carbide and graphite using the full-factorial design. The wear rates of A356/10SiC composite material and A356/10SiC/1Gr and A356/10SiC/3Gr hybrid composites have been analyzed. The composites were obtained by a modified compocasting procedure. Tribological tests were performed on a block-on-disc tribometer without lubrication. The testing included sliding speeds of 0.25 and 1.0 m/s, normal loads of 10 and 20 N, and sliding distances of 300 and 900 m. The analysis of the obtained results was performed using the full-factorial method based on the signal-to-noise (S/N) ratio. The effects of load, sliding speed, weight percentage of graphite reinforcement, and sliding distance on the wear rate are 38.99, 17.87, 13.95, and 11.25%, respectively. The best tribological characteristics were exhibited by the A356/10SiC/1Gr hybrid aluminum composite.     

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.     

Ekonol/石墨/MoS2填料对PTFE力学和摩擦磨损性能的影响

研究了Ekonol含量对Ekonol／石墨／MoS2／P，PTFE复合材料的力学性能、摩擦磨损性能的影响，以及滑动速度、载荷对材料摩擦磨损性能的影响；用扫描电子显微镜观察了复合材料磨损后的表面形貌，并探讨了其磨损机制。结果表明：加入填料降低了材料的拉伸强度和弯曲强度，但提高了弯曲模量和硬度；同时填料能提高材料的磨损性能，但使摩擦因数升高了；当Ekonol含量较低时，磨损机制为粘着磨损，随着填料含量的增加，Ekonol分散到基体中，起到了承载作用，阻止了PTFE基体的带状破坏，磨损机制为疲劳磨损和轻微的粘着磨损；摩擦因数随载荷的增大而减小，随滑动速度的增大而增大，在相同的滑动时间内，磨痕宽度随载荷和滑动速度的增大而增大。     

Boric Acid Self-Lubrication of B2O3-Filled Polymer Composites

Utility of boric oxide particles in PTFE and epoxy composite materials, in sliding contact with stainless steel, is explored. Boric oxide filler can provide PTFE with a two-decade reduction in wear rate, to 10^?5 mm₃/N-m. With adequate ambient humidity reduced wear rate can be achieved without inducing counterface abrasion, and the friction of PTFE is further reduced slightly. In such environments, boric oxide fillers can also reduce friction coefficient of epoxy from μ>0.7 to as low as μ=0.07. This lubrication mechanism results from replenishment of lubricous boric acid lamellar solid provided to the sliding interface by reaction of boric oxide with ambient water. Maintenance of the lubricating effect depends upon a sufficient rate of boric acid formation, relative to subsequent removal by wear. It is demonstrated that this formation/removal balance is affected by relative humidity and volume fraction of boric oxide filler, as well as normal load and sliding speed.     

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.