Tribological behaviours of PA/UHMWPE blend under dry and lubricating condition

Dry-sliding and lubricated friction and wear behaviours of polyamide (PA) and ultra-high molecular weight polyethylene (UHMWPE) blend were studied using a pin-on-disc method (polymer pin sliding against a stainless steel disc) at room environment. The tribological performance of PA and UHMWPE were also investigated for the purpose of comparison. The worn surfaces were examined using a scanning electron microscope (SEM) and optical microscope. It was observed that PA specimen demonstrated highest friction coefficient, UHMWPE the lowest in both dry-sliding and lubricated sliding test. The friction of PA could be sufficiently decreased by blending with UHMWPE. Statistical analysis suggested the relationship between the wear volume loss and the sliding distance could be expressed by a linear model for dry-sliding, while a logarithmic model was determined for lubricated sliding. The difference in wear modes between both sliding series suggested that there was change in the mode of material removal process. The lower wear rate in lubricated sliding was attributed to the elastohydrodynamic or partial elastohydrodynamic lubrication through the development of a continuous lubricant film between the polymer and the counterface, while the high wear rate of the specimens, in dry-sliding test, was mainly caused by fatigue process due to the repeated action of tearing and crack-propagation.     

Friction and Wear Behavior of Ultra-High Molecular Weight Polyethylene Sliding Against GCr15 Steel and Electroless Ni–P Alloy Coating Under the Lubrication of Seawater

The friction and wear behavior of ultra-high molecular weight polyethylene (UHMWPE) sliding against GCr15 steel and electroless Ni-P alloy coating under the lubrication of seawater was investigated and compared with that under dry sliding and lubrication of pure water and 3.5 wt.% NaCl solution, respectively. It was found that under the lubrication of aqueous medium, the friction and wear behavior of UHMWPE mainly depended on the corrosion of counterface and the lubricating effect of the medium. Because of serious corrosion of counterface by the medium, the wear rates of UHMWPE sliding against GCr15 under the lubrication of seawater and NaCl solution were much larger than that under other conditions, and such a kind of wear closely related to the corrosion of counterface can be reckoned as indirect corrosive wear. However, when sliding against corrosion-resistant Ni–P alloy under the lubrication of seawater, the lowest coefficient of friction and wear rate of UHMWPE were obtained, owing to superior lubricating effect of seawater. Moreover, periodic ripple patterns were observed on the worn surfaces of UHMWPE sliding against GCr15 under the lubrication of seawater and NaCl solution, which were ascribed to the intelligent reconstruction of surface microstructure of UHMWPE upon large plowing effect of the counterface asperities. Based on scanning electron microscopic (SEM) and three-dimensional (3D) profile analyses of the worn surfaces of UHMWPE, a stick–slip dynamic mechanism was proposed to illustrate the pattern abrasion of UHMWPE. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The effect of phosphating on the friction and wear properties of grey cast iron

The friction and wear resistance of two commercial manganese phosphate coatings have been evaluated. Grey cast iron wear pins were treated by the two processes and were tested by sliding against a steel disc, under both lubricated and dry sliding wear conditions.Phosphating increases the sliding distance to scuffing as well as the scuffing load, whilst marginally reducing the coefficient of friction. No advantage was found in phosphating dry sliding surfaces.Phosphating reduces the likelihood of adhesive wear in marginal or poorly lubricated sliding couples. The choice of phosphate coating is primarily dependent on the surface finish of the sliding counterface; thin coatings are suitable if the counterface is smooth but thicker coatings are superior against rougher surfaces.     

Tribological properties of plasma nitrided stainless steel against SAE52100 steel under ionic liquid lubrication condition

1Cr18Ni9Ti stainless steel was modified by plasma nitriding. The phase composition of the plasma nitrided layer was examined by means of X-ray diffraction. The friction and wear properties of the modified and unmodified 1Cr18Ni9Ti stainless steel specimens sliding against SAE52100 steel under the lubrication of ionic liquid of 1-ethyl-3-hexylimidazolium hexafluorophosphate (L-P308) and poly α-olefin (PAO) were investigated on an Optimol SRV oscillating friction and wear tester, with the interactions among the modified surface layer and the ionic liquids and PAO to be focused on. The morphologies of the worn surfaces were observed using a scanning electron microscope. The chemical states of several typical elements on the worn surfaces of the modified steel surfaces were examined by means of X-ray photoelectron spectroscopy. Results showed that the modified sample had better anti-wear abilities than the unmodified one, but the modified sample had a slightly higher friction coefficient than the untreated one. This was partly attributed to the change in the hardness and phase composition of the stainless steel surfaces after plasma nitriding and tribochemical reactions between the steel and the lubricant. The resultant surface protective films composed of various tribochemical products together with the adsorbed boundary lubricating film contributed to reduce the friction and wear.     

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.     

Friction and sliding wear of UHMWPE modified cotton fibre reinforced polyester composites

Ultrahigh molecular weight polyethylene (UHMWPE) modified polyester-cotton composites were developed and studied for friction and sliding wear behaviour at different applied loads and UHMWPE concentrations. Sliding wear tests were conducted by using pin-on-disc apparatus. Composites in the form of the pin were tested against EN-24 steel disc. The specific wear rate of polyester reduced on reinforcement of cotton and on addition of UHMWPE. The coefficient of friction of polyester resin increased on cotton reinforcement and reduced significantly on addition of UHMWPE in cotton polyester composite. The composites exhibited reductions in specific wear rate against the normal load in the specimens those containing 7.41 or higher volume percent of UHMWPE. The significant reduction in wear rate of UHMWPE modified polyester-cotton composite has been discussed with the help of SEM observations of worn surfaces and coefficient of friction. The addition of 14.19 vol.% UHMWPE in polyester resin brought down the value of μ to nearly half to that of polyester resin and 1/3rd of cotton polyester composite.     

The influence of bone and bone cement debris on counterface roughness in sliding wear tests of ultra-high molecular weight polyethylene on stainless steel

Studies of explanted hip prostheses have shown high wear rates of ultra-high molecular weight polyethylene (UHMWPE) acetabular cups and roughening of the surface of the metallic femoral head. Bone and bone cement particles have also been found in the articulating surfaces of some joints. It has been proposed that bone or bone cement particles may cause scratching and deterioration in the surface finish of metallic femoral heads, thus producing increased wear rates and excessive amounts of wear debris. Sliding wear tests of UHMWPE pins on stainless steel have been performed with particles of different types of bone and bone cement added. Damage to the stainless steel counterface and the motion of particles through the interface have been studied. Particles of bone cement with zirconium and barium sulphate additives and particles of cortical bone scratched the stainless steel counterface. The cement particles with zirconium additive produced significantly greater surface damage. The number of particles entering the contact and embedding in the UHMWPE pin was dependent on particle size and geometry, surface roughness and contact stress. Particles are likely to cause surface roughening and increased wear rates in artificial joints.     

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.     

Wear resistance and anti-sticking properties of duplex treated forming tool steel

The aim of this work was to investigate the potential of using hard physical vapour deposition (PVD) coatings on forming tools, as well as to determine the influence of plasma nitriding on the load-carrying capacity and wear resistance of coated tool surfaces. A load-scanning test rig was used for evaluation, where duplex treated cold work tool steel samples were loaded against soft austenitic stainless steel and hardened ball bearing steel, respectively. Four different coatings (TiN, TiB₂, TaC and DLC) and two substrate treatments (hardening and plasma nitriding in two different gas mixtures) were included.Plasma nitriding alone significantly improved the friction, wear, and anti-sticking properties of the tool steel. PVD coating, and especially PVD coating of nitrided tool steel further improved the performance. Therefore, from the point of view of tool life as well as work peace surface quality, the DLC coating with its excellent anti-sticking properties and sufficiently good wear resistance represent the best solution for forming tool applications of austenitic stainless steel.     

Wear and corrosion wear of medium carbon steel and 304 stainless steel

Wear and corrosive wear involve mechanical and chemical mechanisms and the combination of these mechanisms often results in significant mutual effects. In this paper, tribological behavior, X-ray peak broadening, and microstructure changes of carbon steel AISI 1045 and stainless steel AISI 304 samples under simultaneous wear and corrosion were investigated and the results were compared with those obtained from dry wear tests. 3.5 wt.% NaCl solution was used as the corrosion agent and a pin-on-disk tribometer was employed to perform wear and corrosive wear tests.X-ray diffraction measurements have shown that by increasing the applied load, the worn surfaces of carbon steel samples reached a constant strain at which fracture and wear occurred. Whereas in 304 stainless steel samples, by increasing the applied load, broadening of X-ray diffraction peaks was decreased.Wear tests of carbon steel and stainless steel samples have shown smaller weight losses and lower friction coefficient in the presence of corrosive environment. Study of worn surfaces suggested that depending on wear environment and applied load, different features of wear mechanisms were involved.     

Large-scale friction and wear tests on a hybrid UHMWPE-pad/primer coating combination used as bearing element in an extremely high-loaded ball-joint

The surfaces of a heavily loaded ball-joint were initially covered with a sliding spray and suffer wear. A solution is found by incorporating UHMWPE pads (Ultra high molecular weight polyethylene) with a carbon fibre/epoxy reinforced ring as sliding material into the chairs of the structure, while the steel ball-side is covered with a Zn-phosphate primer coating, protecting against corrosion. The local static and dynamic behaviour of the hybrid UHMWPE pads in contact with steel or Zn-coated counterfaces has been large-scale tested on loading capacity, low friction and wear resistance. For protection of the sliding counterface against wear, a polymer lip covering the carbon ring has been experimentally designed to flow over the carbon ring under high contact pressures, assuming the retained polymer disc under hydrostatic conditions. As such, the soft coating resists extremely high contact pressures (150 MPa) with good adhesion to the steel ball. However the application method should be carefully selected, sprayed coatings are the most favourable for low initial static friction. Calculated bulk and flashtemperatures revealed that the UHMWPE melting temperature is not exceeded, although softening of the coating under high contact pressures may be favourable for a ‘self-repairing’ ability. Pre-sliding creep and intermediate wear paths as manifesting in the ball-joint were simulated, indicating that the maximum design coefficient of friction is not exceeded. Test results are compared to FEM-calculations to verify the practical applicability of the modified sliding system.     

Experimental analysis of tribological behavior of UHMWPE against AISI420C and against TiAl6V4 alloy under dry and lubricated conditions

Friction and wear behavior of ultra-high molecular weight polyethylene (UHMWPE) sliding against AISI420C austenitic stainless steel and against TiAl6V4 alloy under dry and lubricated conditions were investigated with a reciprocating pin-on-flat tribometer for comparative purposes. The tests were conducted by varying frequency of the pin alternative motion and the applied normal load. For the tests in lubricated conditions a fluid containing a large amount of sodium hyaluronate has been chosen. By using an electronic precision balance the wear mass loss of the UHMWPE samples was evaluated accordingly. Friction is greatly reduced by the presence of UHMWPE and this is believed to be due to the formation of a lubricating film of UHMWPE in the contact zone. Furthermore, the experimental investigation shows that the AISI420C/UHMWPE gives, in dry conditions, better values in the wear rate and in the friction coefficient than the TiAl6V4/UHMWPE.     

自补偿摩擦表面微观形貌分析

进行了钢－铜摩擦副的原始表面、常规润滑油和自补偿滑油润滑下的表面微观形貌测试和分析;对自补偿润滑下和常规润滑下钢、铜表面的粗糙度和表面轮廓特征参数进行了比较;研究了载荷、摩擦行程对自补偿润滑下钢、铜表面微观形貌的影响;得出了钢－铜摩擦副的磨损在一定范围内与载荷无关、其磨损不随摩擦行程线性增加、自补偿添加剂ＳＷ４更适应于重载工况和经过大的摩擦行程后仍起作用等结论。     

Comparative study of micro- and nano-ZnO reinforced UHMWPE composites under dry sliding wear

This is a comparative study between ultra-high molecular weight polyethylene (UHMWPE) reinforced with micro-zinc oxide (ZnO) and nano-ZnO under different filler loads. These composites were subjected to dry sliding wear test under abrasive conditions. The micro- and nano-ZnO/UHMWPE composites were prepared by using a hot compression mould. The wear and friction behaviours were monitored using a pin-on-disc (POD) test rig. The pin-shaped samples were slid against 400 grit SiC abrasive papers, which were pasted, on the stainless steel disc under dry sliding conditions. The worn surfaces and transfer film formed were observed under the scanning electron microscope (SEM). Experimental results showed that UHMWPE reinforced with micro- and nano-ZnO would improve the wear behaviour. The average coefficient of friction (COF) for both micro- and nano-ZnO/UHMWPE composites were comparable to pure UHMWPE. The weight loss due to wear for nano-ZnO/UHMWPE composites are lower compared to micro-ZnO/UHMWPE and pure UHMWPE. The optimum filler loading of nano-ZnO/UHMWPE composites is found to be at 10 wt%. The worn surface of ZnO/UHMWPE composites shows the wear mechanisms of abrasive and adhesive wear. Upon reinforcement with micro- and nano-ZnO, the abrasive and adhesive wear of worn surfaces transited from rough to smooth.     

Acceleration of corrosive wear of duplex stainless steel by chloride in 69% H3PO4 solution

Plots of corrosive wear loss with load and anodic polarization curves during friction were examined for duplex stainless steel (DSS) in 69% H₃PO₄ solution with or without Cl⁻ by a pin-on-ring apparatus. Morphology of tracks and debris was observed in a scanning electron microscope. Variation of Vicker hardness of worn surface was also tested. The defects in wear subsurface were analysed by means of the positron annihilation technique (PAT) and a transmission electron microscope (TEM). The results show that the acceleration of chloride on corrosive wear of the steel is due to the brittle-fracture of the worn surface.     

Sliding contacts for the pharmaceutical industry: failure analysis and dry sliding tests for the replacement of hard Cr on AISI 316L steel

Several alternatives were compared for the replacement of hard electroplated Cr coating to improve the tribological properties of the AISI 316L austenitic stainless steel for pharmaceutical packaging applications, including low temperature carburizing (LTC), thermal spray coatings (Al₂O₃-13TiO₂, WC-17Co), substitution of the AISI 301 reference counterface with polymeric materials (PTFE, UHMWPE, PEEK). In dry sliding block on ring tests, the LTC AISI 316L cylinders lead to the lowest wear rates of the AISI301 sliders under low loads (up to 10 N). When considering the polymer vs. uncoated AISI 316L couple, PEEK and UHMWPE lead to lower friction and comparable wear rates with respect to the reference couple (AISI 301 vs. Hard Cr coated-AISI 316L) in the whole range of tested loads.     

Tribological behaviour of DLC coatings compared to different materials used in hip joint prostheses

The goal of the study carried out in the laboratory was to quantify the wear and the friction of two materials used for the manufacturing of hip prostheses. Tests used had to obtain in a short time the tribological behaviour laws of the materials. Tests on a hip simulator have been excluded because their cost and their duration were too high for a program of preliminary development of new materials.

To amplify wear phenomena, dry friction tests were carried out for two configurations: ball-on-disc and pin-on-disc. The influence of the contact pressure at constant sliding velocity on the wear of materials has been clearly shown.

Results obtained with several different tested materials (stainless steel/UHMWPE, stainless steel+DLC coating/UHMWPE, stainless steel+DLC coating/stainless steel+DLC coating, titanium alloy+DLC coating/UHMWPE, titanium alloy+DLC coating/titanium alloy+DLC coating, zirconium dioxide/UHMWPE, alumina/UHMWPE, alumina/alumina) have shown the superiority of DLC coatings. Promising results obtained during this study are in the validation stage on a hip simulator.     

Tribological Behavior of Tin-Based Babbitt Alloy Lubricated by Seawater

In this article, the tribological behaviors of tin-based Babbitt alloy ZChSnSb 8–8 sliding against AISI 302 stainless steel lubricated by seawater were investigated. The results indicated that the friction coefficient decreases with increasing load and sliding speed, and the wear rate increases slightly with load but decreases with sliding speed. The low friction coefficient and wear rate are attributed to the unique “concrete structure” and seawater. As a lubrication medium, seawater has lubricating, cooling, and corrosive effects on the sliding couple.     

Transfer film bonding and wear studies on CuS-nylon composite sliding against steel

The tribological behaviour of nylon 11 reinforced with lead sulphide filler was studied. The composite specimens with different filler proportions were made by compression moulding. The friction and wear experiments were run under ambient conditions in a pin-on-disk machine with the composite pin riding on the flat surface of a steel disk. It was found that 35 vol.% PbS-nylon composite had the highest wear resistance. The friction and wear tests were run with this composite at different loads, speeds and counterface roughnesses. The wear rate increased considerably when the load was increased from 19.6 N to 39.2 N and the sliding speed from 1 m/s to 2 m/s, but the effect of these increases on the coefficient of friction was very small. The wear rate also increased abruptly when the surface roughness was increased from 0.11 to 0.3 μm but the coefficient of friction was not affected. It was found that the wear process was dominated by the transfer film that formed on the counterface. The transfer film and the worn surfaces were studied by scanning electron microscopy. XPS analysis indicated chemical bonding between the polymer composite transfer film and the steel counterface.     

Tribological behaviour of plasma nitrided Ti-5Al-2Nb-1Ta alloy against UHMWPE

A detailed study has been made on the wear behaviour of untreated and plasma nitrided Ti-5Al-2Nb-1Ta orthopaedic alloy against ultra high molecular weight polyethylene (UHMWPE) using pin on disc tribometer under lubricated conditions. The effects of nitriding temperature and nitriding time on the basis of the evolution of the wear volume loss and friction coefficient were investigated. The wear resistance of the plasma nitrided alloys increased considerably when compared to the untreated alloy. The wear debris identified using X-ray diffraction measurements indicated the formation of titanium oxide and titanium oxynitride particles. The wear rate was found to increase with increase in load and sliding velocity.