Constant Wear Rate Research Articles

Sliding wear characteristics of Mg/Si3N4 nanocomposites at room and elevated temperatures

• Mg/Si 3 N 4 nanocomposites were prepared through ultrasonic-assisted stir casting. • A uniform dispersion of Si 3 N 4 nanoparticles was achieved for the composites. • Si 3 N 4 nanoparticles increased the microhardness at room and elevated temperatures. • The wear rate of the Mg/Si 3 N 4 nanocomposites was almost constant up to 200 °C. Magnesium's future use in automobile powertrain applications will necessitate superior wear resistance at elevated temperatures. To address this problem, the current work utilized Silicon Nitride (Si 3 N 4 ) nanoparticles to increase the wear resistance of magnesium at room and elevated temperatures (100 °C, 150 °C, and 200 °C). Using the ultrasonic-assisted stir casting process, 1.5 vol% of Si 3 N 4 nanoparticles were homogeneously reinforced in the pure magnesium matrix. Notably, the hardness of the nanocomposites increased at both room and higher temperatures. Furthermore, the inclusion of Si 3 N 4 nanoparticles resulted in a nearly constant wear rate up to 200 °C, indicating enhanced wear resistance of nanocomposites at high temperatures. The worn pin surfaces of pure magnesium revealed abrasion, severe adhesion, and delamination wear as the dominant mechanisms, whereas oxidation was prevalent in nanocomposites.

Development and Validation of a Finite Element Model of Wear in UHMWPE Liner Using Experimental Data From Hip Simulator Studies.

The wear of acetabular liner is one of the key factors determining osseointegration and long-term performance of total hip joint replacement implants. The experimental measurements of wear in total hip replacement components are time and cost-intensive. While addressing this aspect, a finite element model of a hip joint bearing consisting of zirconia-toughened alumina femoral head and ultrahigh molecular weight polyethylene liner was developed to predict the dynamic wear response of the liner. The Archard-Lancaster equation, consisting of surface contact pressure, wear rate, and sliding distance, was employed to predict the wear of the acetabular liner. The contact pressure and wear at the articulating surface were found to decrease over time. A new computational method involving three-dimensional point clouds from the finite element analyzed results were used to construct wear maps. The model was able to predict the linear wear, over 2 × 106 cycles with relative errors ranging from 9% to 36% when compared to the published results. The increasing error percentage occurring primarily from the use of a constant wear rate was reduced to a maximum of 17% by introducing a correction factor. The volumetric rate was predicted with a maximum relative error of 7% with the implementation of the correction factor. When the model was implemented to study acetabular liners of diameters ranging from 28 to 36 mm, the linear wear was seen to decrease with an increase in femoral head diameter, which is in agreement with the clinical data. This study emphasizes the need to develop more such FEA-based computational studies to reliably predict and correlate with experimentally measured temporal evolution of wear of load-bearing articulating joints.

Wear characteristics of nanoporous alumina and copper filled nanocomposite coatings

Anodisation of pure aluminium under certain conditions, form nanoporous alumina (NPA) with highly ordered pores. High interface strength and hardness make NPA an ideal tribological coating. The nanopores can be filled with metals using electrodeposition to give rise to a nanocomposite coating with better tribological properties. In this study, the friction and wear behaviour of NPA and copper filled nanocomposite coatings are studied under dry reciprocation conditions with a hard zirconia ball. The coefficient of friction of NPA and the nanocomposite is found to be about 0.95. Wear particles are generated by the propagation of surface microcracks and possibly by compaction. From the SEM images of the wear tracks, it is found that these wear particles form a protective tribolayer. The wear process of the coatings is characterised by three distinct regimes of constant wear rate, low wear, and catastrophic failure. The coating fails, possibly by radial cracking, when the thickness of the unworn coating reaches a critical value. Uniform filling of copper in the nanopores is found to enhance the wear life.

Study of wear and friction characteristics of powder lubricants under extreme pressure conditions

Powder lubricants are more efficient in lubrication than oil at extremely hot conditions and at high vacuum conditions. This work investigates the wear and the friction characteristics of metals lubricated with three different powders CuO, MoS2 and ZrO2 in dry state under extreme contact pressure situations. Reciprocating sliding wear tests were performed to determine the lubricating characteristics of these powder lubricants under varying combinations of temperatures and loads based on central composite design. SEM with EDS (Energy Dispersive X-ray Spectroscopy) analysis was carried out to analyze the surface morphology of the mechanically formed oxide film. The results shows that powders could be effectively used as solid lubricant in dry conditions. It was observed that CuO acted as better powder lubricant for steel specimen when constant wear rate is required at varying temperature and load situations.

Characterizing wear behaviors of edible hydrogels by kernel-based statistical modeling

Hydrogels are used in multiple industries; although hydrogel deformation and wear behaviors can be a good indicator for their functionality, there are no available models for characterizing hydrogel deformation–wear behaviors. This study characterized wear behaviors of casein (3–5% w/w, 200 mM NaCl), κ-carrageenan (0.8–1.2% w/w, 100 mM NaCl), and whey protein gels (13% w/w, 50–150 mM NaCl) at room temperature (20 °C) under several normal forces (0.1–1.5 N). A kernel-based model was used to characterize hydrogel wear behavior by separating the deformation–wear process deformation-dominant, constant wear rate, and failure regions. Higher normal force and lower polymer concentration showed higher constant wear rates and lower durability. The kernel model was able to characterize hydrogel wear-deformation behaviors and is useful for industrial applications.

Application of SiC particles coated with a protective Ni layer for production of Ni/SiC co-electrodeposited composite coatings with enhanced tribological properties

In this paper, the mechanical properties of composites consisting of electroplated Ni and co-electrodeposited SiC particles, coated with a thin protective layer of Ni, were studied. The protective layer was on the SiC particles prior to adding them to the electrolyte bath. It was demonstrated that due to the application of the protective layer it was possible to decrease sliding friction force, and improve the wear resistance, of the composite coatings in comparison with standard electroplated composite coatings made of Ni and co-electrodeposited pure SiC particles. Coating SiC particles with Ni was achieved by means of a PVD process. The main advantage of this step is avoiding oxidation of the surface of the particles during the contact with an electrolyte. Particles protected from oxidation lead to stronger interfacial bonding between the matrix and the reinforcement. Furthermore, better bonding protects the SiC particles from being extracted from the matrix by a counter-probe during friction and wear tests. The influence of the particle's concentration is studied. A smaller friction force and constant wear rate was observed.

Friction and wear behaviour of cemented carbide tool materials sliding against Al2O3 and Si3N4 ceramics under dry condition

To investigate the friction and wear behaviour of YG6 cemented carbide during sliding against Al2O3 and Si3N4 ceramics, the ball-on-disc friction and wear test were carried out under dry condition at different speeds and loads. The friction coefficients were collected by the tribo-tester and the wear rate were calculated based on the wear quality loss. It was shown that friction coefficient was slightly dependent on sliding speeds and loads during sliding against Al2O3 and Si3N4 ceramics. However, the wear rate of cemented carbide was highly dependent on sliding speeds and loads during sliding against Al2O3 ceramics. On the contrast, cemented carbides showed a higher friction coefficient but a lower and constant wear rate during sliding against Si3N4 ceramics. The main wear mechanism of cemented carbide was abrasive wear during against Al2O3 ceramics, but diffusion wear and oxidative wear during against Si3N4 ceramics. The overall understanding of friction and wear behaviour for cemented carbide during sliding against Al2O3 and Si3N4 ceramics under dry condition could widen the application range of cemented carbides and promote the development of high speed dry machining technology.

Fretting wear of composite ceramic coating produced on D16 aluminum-based alloy using microarc oxidation

The mechanism of the wear of a composite ceramic coating, which has been produced on the D16 aluminum-based alloy using microarc oxidation, under low-amplitude reciprocal friction (fretting) is studied. The ball-on-plane arrangement in which a diamond ball slides reciprocally against a flat specimen covered with the microarc-oxidation coating is considered. The three following regions of the fracture of the coating have been identified: the moderate wear range, which is characterized by a constant wear rate and in which a smoothed wear spot is formed; the severe wear range, which is characterized by the partial delamination of the top layer of the coating; and the extreme wear range, which is characterized by the cracking of the coating through its entire thickness up to the metal. Based on the experimental results, the boundary of the transition to the inoperative region of the extreme wear of the coating has been determined over the entire ranges of the load and displacement under study.

Efficient Steady-State Computation for Wear of Multimaterial Composites

Traditionally, iterative schemes have been used to predict evolving material profiles under abrasive wear. In this work, more efficient continuous formulations are presented for predicting the wear of tribological systems. Following previous work, the formulation is based on a two parameter elastic Pasternak foundation model. It is considered as a simplified framework to analyze the wear of multimaterial surfaces. It is shown that the evolving wear profile is also the solution of a parabolic partial differential equation (PDE). The wearing profile is proven to converge to a steady-state that propagates with constant wear rate. A relationship between this velocity and the inverse rule of mixtures or harmonic mean for composites is derived. For cases where only the final steady-state profile is of interest, it is shown that the steady-state profile can be accurately and directly determined by solving a simple elliptic differential system—thus avoiding iterative schemes altogether. Stability analysis is performed to identify conditions under which an iterative scheme can provide accurate predictions and several comparisons between iterative and the proposed formulation are made. Prospects of the new continuous wear formulation and steady-state characterization are discussed for advanced optimization, design, manufacturing, and control applications.

Microscratching Characterization of the Wear-in of UHMW Polyethylene in Prostheses

A new measurement technique of prosthesis wear by microscratching has been demonstrated. The technique has been applied in a study of the backside wear of a UHMW polyethylene tibial insert of a rotating platform knee prosthesis. Four disc-shaped UHMW polyethylene plugs, prepared with 5-μm deep microscratches, were carefully recessed into the backside of the tibial insert. It was demonstrated that the scratches are not affected by creep under static load. A realistic in vitro wear simulation experiment was performed over 0.8 × 106 flexion cycles. SEM and AFM show that following the experiment the initial microscratches are effectively absent in all four locations with only residual depressions observed. This implies that typically at least 5 μm of polyethylene material was worn over the first 0.8 × 106 cycles by processes other than creep. Evidence from AFM and SEM indicates the in-fill and reintegration of polyethylene wear particles into residual scratch depressions. This supports a two-phase model of the wear process that has been independently confirmed by radioisotope tracing. For an initial wear-in phase, the model implies large, but rapidly decreasing, wear, resulting from abrasive wear and a competition between the loss and the reintegration of wear particles. The in vitro wear-in of the backside may typically produce a wear debris volume of 8.5 mm3. In addition to wear-in, the model assumes a much lower, constant long-term wear rate. The model has been used to correct published backside wear rates for the effects of the wear-in phase. A best estimate of 0.7 mm3/106 cycles has been determined for the long-term in vitro backside wear rate of a tibial insert in a rotating platform design.

Evaluation of factors influencing deep cryogenic treatment that affect the properties of tool steels

Deep cryogenic treatment (DCT) of tool steels is used as an additive process to conventional heat treatment and usually involves cooling the material to liquid nitrogen temperature (−196 °C). This kind of treatment has been reported to improve the wear resistance of tools. In this study, the Taguchi method was used to identify the main factors of DCT that influence the mechanical properties and the wear resistance of the powder metallurgically produced cold-work tool steel X153CrVMo12 (AISI D2). Factors investigated were the austenitizing temperature, cooling rate, holding time, heating rate, and tempering temperature. In order to study the significance of these factors and the effect of possible two-factor interactions L 27(3 13), an orthogonal array (OA) was applied to conduct several heat treatments, including a single DCT cycle directly after quenching prior to tempering. The results show that the most significant factors influencing the properties of tool steels are the austenitizing and tempering temperatures. In contrast, the parameters of deep cryogenic treatment exhibit a lower level of significance. Further investigations identified a nearly constant wear rate for holding times of up to 24 h. The wear rate reaches a minimum for a longer holding time of 36 h and increases again with further holding.

Polymer tribology by combining ion implantation and radionuclide tracing

Radionuclide tracers were ion implanted with three different techniques into the ultra-high molecular weight polyethylene polymer. Tracer nuclei of (7)Be were produced with inverse kinematics via the reaction p((7)Li,(7)Be)n and caught by polymer samples at a forward scattering angle with a maximum implantation energy of 16 MeV. For the first time, (97)Ru, (100)Pd, and, independently, (111)In have been used as radionuclide tracers in ultra-high molecular weight polyethylene. (97)Ru and (100)Pd were recoil-implanted following the fusion evaporation reactions (92)Zr((12)C,alpha 3n) (97)Ru and (92)Zr((12)C,4n)(100)Pd with a maximum implantation energy of 8 MeV. (111)In ions were produced in an ion source, mass-separated and implanted at 160 keV. The tribology of implanted polymer samples was studied by tracing the radionuclide during mechanical wear. Uni-directional and bi-directional sliding apparatus with stainless steel actuators were used. Results suggest a debris exchange process as the characteristic feature of the wear-in phase. This process can establish the steady state required for a subsequently constant wear rate in agreement with Archard's equation. The nano-scale implantation of mass-separated (111)In appears best suited to the study of non-linear tribological processes during wear-in. Such non-linear processes may be expected to be important in micro- and nanomachines. (C) 2010 Elsevier B.V. All rights reserved.

Microstructural evolution during high temperature sliding wear of Mg–3% Al–1% Zn (AZ31) alloy

Deformation microstructures generated during the high temperature sliding of a wrought Mg–3% Al–1% Zn alloy (AZ31) were investigated to delineate the micromechanisms of wear and material transfer to a tool steel counterface. Dry pin-on-disc type tests were conducted at 673 K. Optical profilometry and analytical microscopy revealed that material transferred to the counterface was heavily deformed and partially recrystallized. The subsurface grains beneath the contact surface were subjected to large plastic strains, and experienced dynamic recrystallization and growth as a result. Grain growth occurred in the subsurface zone beneath the recrystallized zone and followed a parabolic kinetic law with an activation energy of 35 kJ/mol. Surface damage and material transfer events proceeded in a cyclical manner, bringing the sliding process to a dynamic equilibrium, and leading to a constant wear rate.

Tribological and structural properties of lubricating films of Al–4Si–20Pb alloy during dry sliding at different temperatures

The friction and wear behaviour of an hot extruded Al–4Si–20Pb alloy was investigated under dry conditions in a temperature range 25–200 °C using a pin-on-disc type wear testing machine. The results show that the material demonstrates good friction and wear properties, the almost constant wear rate and lowest level in coefficient of friction at room temperature and 373 K is attributed to a lubricating film covering almost the entire worn surface. X-ray photoelectron spectroscopy and X-ray analyses reveal that the lubricating film is a mixture of Fe2O3, Pb4SiO6 and a small amount of Fe2O3 at room temperature, and a mixture of Pb4Al12(SiO3)7, SiO2, Al2O3 and a small amount of Fe2O3 at 373 K.

Application of the ASTM Loop Abrasion Test to Cylindrical Specimens

Abstract The loop abrasion test (based on ASTM G 174-03) was modified to accommodate cylindrical specimens in place of the usual flat specimens. Hardened AISI 52100 steel, a galling-resistant stainless steel (Nitronic 50), transformation-toughened zirconia ceramic, and an advanced composite containing Ni3Al and TiC (cermet) were used to validate the new testing geometry. The weight change and the scar width were measured, and the calculated wear volumes for each metric were compared with very good correlation. Each test was interrupted periodically in order to determine the effect of sliding distance on the wear rate. In general, a higher wear rate was observed during wear-in followed by a nearly constant steady-state wear rate. The initial high wear rate was contributed primarily by the fresh abrasive and secondarily by the high contact stress. The loop abrasion test has good repeatability and sensitivity for ranking materials. The abrasion resistance of both the cermet and the zirconia was much higher than that of Nitronic 50 and hardened 52100 steel. Even though the hardness of the cermet is lower than zirconia, it had the highest abrasion resistance in this study. Comparative tests on cylindrical and traditional flat specimens (per ASTM G 174-03) showed similar wear behavior with slightly higher wear rate for the cylindrical specimens due to higher contact stress.

Assessing the pattern of femoral head penetration after total hip arthroplasty

We evaluated temporal changes in wear rates among 205 primary cementless total hip arthroplasties that had minimum 10-year follow-up and at least 6 follow-up x-rays. Using the pelvic anteroposterior x-rays from each hip, two-dimensional head penetration was measured and wear rates were calculated using several techniques. The average wear rate for the study population did not demonstrate evidence of accelerated wear at 10- to 18-year follow-up. As an increasing number of follow-up x-rays were included in the least-squares linear regression used to calculate the wear rate, the 95% confidence interval associated with the wear rate for an individual hip tended to progressively decrease. These results indicate that a constant wear rate is a reasonable assumption for modeling clinical wear data. Although we cannot quantify the effects of polyethylene oxidation, femoral head roughening, debris accumulation, or activity level changes, the combination of these factors is not leading to clinically perceptible accelerated wear at intermediate to long-term follow-up in this heterogeneous population of cups representing our institutional experience.

Tribological and structural properties of lubricating films of Al–4Si–20Pb alloy during dry sliding at different temperatures

Abstract The friction and wear behaviour of an hot extruded Al–4Si–20Pb alloy was investigated under dry conditions in a temperature range 25–200 °C using a pin-on-disc type wear testing machine. The results show that the material demonstrates good friction and wear properties, the almost constant wear rate and lowest level in coefficient of friction at room temperature and 373 K is attributed to a lubricating film covering almost the entire worn surface. X-ray photoelectron spectroscopy and X-ray analyses reveal that the lubricating film is a mixture of Fe2O3, Pb4SiO6 and a small amount of Fe2O3 at room temperature, and a mixture of Pb4Al12(SiO3)7, SiO2, Al2O3 and a small amount of Fe2O3 at 373 K.

Dry sliding wear behavior of hot extruded Al–Si–Pb alloys in the temperature range 25–200 °C

The wear behavior of hot extruded Al–Si–Pb alloys was investigated under dry conditions in a temperature range 25–200 °C using a pin-on-disc type wear testing machine. The results show that the microstructure and mechanical properties can be greatly improved and porosity can be significantly decreased by hot extrusion. These factors contribute to great increase in wear resistance of hot extruded Al–Si–Pb alloys. Optical observation and X-ray photoelectron spectroscopy (XPS) analysis reveal that at room temperature the almost constant wear rate and lowest level in coefficient of friction at high load levels for Al–Si–Pb alloys with more than 15 wt.% lead are due to a film of lubricant covering almost the entire worn surface. This film is a mixture of different constituents containing Al, Fe, Si, O and Pb, in which Pb exists in the form of Pb 4SiO 6. In the case of Al–Pb–Si alloy with 15% lead worn at 100 °C, X-ray analysis reveal that constant wear rate and lowest level in coefficient of friction are caused by a film of lubricant with a main constituent of Pb 4Al 2(SiO 3) 7. At 200 °C, no film of lubricant was formed on the worn surface of Al–Pb–Si alloy with 15% lead.

Improvement of the wear behavior of stircast Al–Si–Pb alloys by hot extrusion

The wear behavior of as-cast and hot extruded Al–Si–Pb alloys were investigated under dry conditions using a pin-on-disc type wear testing machine. The results show that the microstructure and mechanical properties can be greatly improved and porosity can be significantly decreased by hot extrusion. These factors contribute to great increase in wear resistance of hot extruded Al–Si–Pb alloys. Optical observation and X-ray photoelectron spectroscopy (XPS) analysis reveal the almost constant wear rate at mediate load levels. Better resistance to seizure for Al–Si–Pb alloys with more than 15 wt% lead are due to a film of lubricant covering almost the entire worn surface. This film is a mixture of different constituents containing Al, Fe, Si, O and Pb.

Process and wear behavior of monolithic SiC and short carbon fiber-SiC matrix composite

The process and wear behavior of monolithic SiC and 10 vol. % short carbon fiber-SiC matrix (C-SiC) composite have been studied. The results indicate that, among ethyl alcohol, acetone, n-hexane and n-octyl alcohol, n-octyl alcohol was the most effective dispersing agent in dispersing both SiC powder and short carbon fiber. Among AlN, Al2O3, B4C, graphite, AlN/B4C, AlN/graphite, B4C/graphite and Al2O3/B4C, the most effective sintering aid for the fabrication of SiC and C-SiC composite was a mixture of 2 wt% AlN and 0.5 wt% graphite. The monolithic SiC hot-pressed at 2100°C exhibited higher density but lower flexural strength than those hot-pressed at 2000°C due to a grain growth effect. For the C-SiC composite, both density and strength of the composite hot-pressed at 2100°C were generally higher than those hot-pressed at 2000°C. The density and strength of C-SiC composite were lower than those of monolithic SiC under the same hot pressing conditions due to a higher porosity level in the composite. When monolithic SiC slid against C-SiC composite, the weight losses of SiC and the composite were each less than that of self-mated SiC or self-mated C-SiC. In the self-mated SiC tribosystem, a mechanically stable film could not be established, resulting in an essentially constant wear rate. When sliding against C-SiC, a thin, smooth and adherent debris film was quickly formed on the SiC surface, resulting in a lower wear.