Increase In Wear Volume Research Articles

Electrotribochemical formation of abrasive nano-carbon particles under electrified conditions on lubricated sliding contacts

Electric vehicle (EV) mobility represents a transformative shift in achieving better energy security, environmental cleanliness, and economic prosperity. Despite recent advancements in EV technology, several challenges persist in tribology and lubrication fronts that can hamper their long-term reliability, performance, and efficiency. In this work, we explored the tribological performance of four commercially available driveline lubricants under non-electrified and electrified sliding conditions using AISI 52100 bearing steel. The results confirmed that passing of electricity through the contact interface exacerbate the wear damage (causing as much as a 5-fold increase in wear volume). Using Raman Spectroscopy, XPS, SEM, ToF-SIMS, and HRTEM, we confirmed that such accelerated wear primarily results from the formation of highly abrasive soot-like amorphous carbon, iron carbide, and other carbonaceous products which result from the decomposition of long-chain hydrocarbon molecules of lubricating oils under electrification. These findings confirm the existence of very complex wear mechanisms in electrified contacts and suggest the need for much improved lubricants and/or materials for future EV applications.

Enhancing high-temperature fretting wear resistance of TC21 titanium alloys by laser cladding self-lubricating composite coatings

Fretting wear is one of the main factors restricting the fastener service reliability for the high-temperature titanium alloys. Enhancing the high-temperature fretting wear resistance of titanium alloys with laser cladding coatings is an effective method. Thus, in this work, a self-lubricating composite coating was designed and fabricated on the surface of TC21 titanium alloy with laser cladding. Special attentions were made to the effect of the fractions of the hard and self-lubricating phases on high-temperature fretting resistance. In addition, the contribution of laser cladding power was also concerned. The primary phases of the self-lubricating composite coatings are α-Co, CaF2, WC, TiC and Cr23C6, and the reasons for the formation of TiC and Cr23C6 are investigated from a thermodynamic point. The prepared composite coatings are dense and uniform. The crystallographic characteristics and the volume fractions of the hard phases (WC, TiC and Cr23C6) and self-lubricating phase (CaF2) were revealed, and the effect of grain size on the coating properties was analyzed. The hardness of the coatings were all maintained around 700 HV0.2, which was significantly higher than that of the substrate. The composite coating significantly improves the friction and wear resistance at 500 ℃. The hard phase was also found to be the most resistant to friction and wear. The frictional performance of the coating gets better when the hard phase and the self-lubricating phase increase. However, the hard phase contributes more to the high-temperature friction and wear resistance than the self-lubricating phase and the wear volume is 1/40 that of substrate. For the laser cladding power, the higher power can lead to a higher fraction of CaF2 but a lower fraction of hard phase, causing a decline in COF but an increase in wear volume. The wear mechanisms of the coating and the substrate were analyzed, the subsurface stress distribution state of the wear scars were further analyzed. The current results present new insights on the anti-wear design strategy to the composite coatings consist of hard and self-lubricating phase.

Comparative study of reciprocating sliding wear of HNBR on the effects of temperature

The wear of the sealing rubber of packers, which are widely used in the field of oil production, has drawn more and more attention nowadays. This research conducted the reciprocating sliding wear tests of hydrogenated nitrile rubber (HNBR) at 20 °C, 60 °C, 100 °C and 140 °C in different downhole mediums (dry, water, crude oil). The results show that the coefficient of friction (COF) curves fluctuate greatly under dry sliding and water medium condition, but keep a stable state in crude oil medium. In dry sliding condition, the average COFs and wear volume increase firstly, then diminish and reach the minimum at 140 °C due to the reduced hardness and matrix binding force. Schallamach waves, little debris and pits feather the worn surface of HNBR at lower test temperature (20 °C and 60 °C). Plastic deformation and cracks occur at 100 °C and 140 °C, indicating the combined mechanism of abrasive wear and fatigue wear at this condition. Both the average COF and wear volume increase slightly with temperature in water and crude oil medium. This paper has guiding significance to improve the sealing performance of packer.

Optimizing the friction behavior of medium entropy alloy via controllable coherent nanoprecipitation

In recent years, FeCrNi medium entropy alloy, a new material with high hardness, strength, ductility, and wear resistance, has been widely studied. In this work, the effect of precipitation volume fraction on the friction behavior of FeCrNi is studied by molecular dynamics simulation. With the increase of precipitation volume fraction, the average friction coefficient shows an upward trend. When the volume fraction of precipitation is between 2.33% and 3.10%, the wear resistance of FeCrNi would be enhanced after the nanoscratching, and the normal force is large, which means that a certain precipitation volume fraction strengthens FeCrNi. Low precipitation volume fraction can effectively reduce the wear volume and wear rate during scratching, thus effectively lowering frictional force and friction coefficient. The interaction between dislocation and precipitation is an important factor that hinders dislocation propagation, leading to the strong dislocation strengthening and the increase of wear volume. This trend is manifested as the increase of normal force and frictional force. The frictional properties of FeCrNi can be optimized with a certain precipitation volume fraction. The findings give a guiding significance for the effect of multiple precipitation on frictional properties of FeCrNi.

Investigation on the effect of coating properties on transient mixed lubrication of gas foil bearing

To reveal the effect of coating properties on the mixed lubrication evolution during the start–stop process of gas foil bearing (GFB), a transient gas mixed lubrication-wear model for coating surface is established. In the developed model, a method of the extended equivalent modulus by the film thickness ratio is proposed, which can extend the classic Greenwood and Tripp contact model for homogeneous materials to the coating contact involving layered materials. Moreover, a gas foil bearing start–stop experiment is conducted to verify the predicted results of the developed model. The effects of coating materials and standard deviation of coating surface on the start–stop performance of GFB are investigated. Within the scope of this article, the results show that during start-up, the gas film pressure first increases and then decreases with the increase in time, the minimum film thickness increases, while the asperity contact decreases. The opposite evolution is observed during shut-down. Compared with uncoated GFB, the friction torque and lift-off speed of GFB with polyimide (PI) and polytetrafluoroethylene (PTFE) are reduced, with PI reducing friction torque by 24.27% and PTFE by 49.03%. The minimum lift-off speed with PTFE is the smallest. The lift-off speed, friction torque, and wear volume increase with the increase in the standard deviation of coating surface. The friction torque and lift-off speed decrease as the start–stop cycle increases until both reach stability. This paper can provide theoretical guidance for the design of the top foil coating surface of GFB.

Microstructure characterization of Co–Cr–Mo–xTi alloys developed by micro-plasma based additive manufacturing for knee implants

This paper reports on effects of adding 2, 4 and 6 wt.% Ti to Co–Cr–Mo by micro-plasma based additive manufacturing (MPBAM) process on density, porosity, microstructure, phase formation, inter-diffusion zones, microhardness, and wear characteristics of the resultant alloy with an objective to develop better material for knee implant applications. Bulk and relative density found to decrease, and porosity increase with increase in Ti % to Co–Cr–Mo alloy. Co–Cr–Mo–4Ti alloy showed more pores and their uniform distribution. Microstructures of Co–Cr–Mo–2Ti and Co–Cr–Mo–4Ti alloys are porous and crack-free. Phase analysis of Co–Cr–Mo–4Ti revealed presence of α-Co, ε-Co, and β-titanium phases (having FCC, HCP, and BCC crystal structure respectively), inter-metallic CoTi2, and lamellar chromium carbides i.e. Cr7C3 and Cr23C6. It is confirmed by the phase mapping also. Inverse pole figure maps did not show any preferential orientation of grains and revealed presence of ε-Co phase matrix with traces of grains of chromium carbides and CoTi2 phases. Increasing Ti% in Co–Cr–Mo alloy increased formation of β-Ti and CoTi2 phases which have less hardness than the carbide phases therefore average microhardness of Co–Cr–Mo–2Ti alloy is found as the highest followed by Co–Cr–Mo–4Ti alloy. Coefficient of friction, specific wear rate, and wear volume increase with increase in Ti% in Co–Cr–Mo alloys due to decrease in microhardness and increase in porosity. It also increased ploughing and delamination in the worn track. This study found Co–Cr–Mo–4Ti as a better knee implant material due to its lesser density, uniform porous structure, absence of cracks, moderate microhardness, and wear characteristics.

Alumina abrasive wheel wear in ultrasonic vibration-assisted creep-feed grinding of Inconel 718 nickel-based superalloy

Blade root with a special fir-tree shape is a critical connection part in an aero-engine. This part has high requirements on the surface finish and geometrical accuracy. At present, the tangential ultrasonic vibration-assisted profile grinding (UVAPG) is an effective method for machining the blade roots. During UVAPG, the wheel wear degrades the surface finish and geometrical accuracy. However, the characteristics of the wheel wear in UVAPG are not fully revealed. This study proposes an analytical wear model by considering the intermittent grinding behavior of a grinding edge, the number of active grinding edges, and the effects of wheel profile on the tool wear. The model is experimentally demonstrated to be applicable to predicting the wear volume in UVAPG with a maximum error of 4.2 %. Based on the model, the tangential ultrasonic vibration increases the average unchanged chip thickness and the number of active grinding edges. UVAPG causes an approximately 22 % increase in wear volume at the steady wear stage compared with the conventional grinding. The wear speeds vary at different regions of a profile wheel. The convex regions represent higher wear speeds than the concave regions on the wheel.

Structural Characteristics and Sliding Friction Properties of 40CrNiMo Steel after Broadband Laser Hardening

The surface of 40CrNiMo steel, which is commonly used for the sprag clutch wedge, is prone to wear. In this study, hardening of the matrix material was conducted by broadband-laser scanning at various scanning speeds. The hardness distribution and structure evolution were analyzed along the vertical direction. Characteristics of the hardened layer were explored using scanning electron microscopy, transmission electron microscopy, and X-ray diffractometry. The friction coefficient, wear amount, and wear morphology of sliding friction against GCr15 steel were investigated under various conditions. The results show that the depth of the hardened zone decreases with increasing scanning speed. Under the experimental power and defocus, a laser scanning speed between 700–1020 mm/min can meet the general surface requirements of the sprag clutch wedge. After laser hardening, the main components of the hardened layer included lath-shaped and needle-shaped martensite and retained austenite. In terms of friction and wear, when the relative movement speed was within 300–500 mm/min, the relative movement speed decreased and the normal force increased, which led to an increase in the friction coefficient and its fluctuation, as well as an increase in wear volume of the hardened layer. The wear mechanism of the hardened layer included abrasive wear, adhesive wear, and oxidative wear. Excessive normal force resulted in obvious delamination of the sample. Within the scope of the experiment, the best laser hardening results were obtained with a scanning speed of 800 mm/min.

High Temperature Dry Tribological Behavior of Nb-Microalloyed Bearing Steel 100Cr6.

100Cr6 steel is one of the most widely used bearing steels and a representative of first-generation bearing steel. Many engineering applications require rolling bearings to run at a high temperature. Therefore, it is necessary to improve the high temperature properties of 100Cr6 steel. In this paper, the effect of Nb on high temperature dry tribological behavior, including worn surface and friction coefficient, was analyzed by a wear test when Nb content was 0.018% and 0.040%. The results show that the microstructure is refined gradually, the hardness is improved, and wear volume decreases by 31.8% at most with the increase of Nb content. At 50 °C, the friction coefficient of 100Cr6 steel can be reduced by adding a small amount of Nb, but this effect will be weakened if the content of Nb is too high. In addition, excess Nb increases the hard precipitation of NbC, which aggravates the abrasive wear and leads to the increase in the depth of the worn surface. At 125 °C, the effect of Nb on tribological properties is weaker. With the increase of temperature, the steel substrate softens, and the oxide particles increase, which aggravates the abrasive wear and oxidation wear and makes the wear volume increase significantly.

The Effect of Toothbrushing Duration on Nickel Chromium Alloy Wear

Nickel-chromium alloy is a preferred material for fixed partial denture due to its low cost as well as good physical and mechanical properties. Tooth brushing using toothpaste produces abrasion on restoration, especially in a long period. This study aimed to observe the effect of toothbrushing duration on the wear of nickel-chromium alloy. Twenty four specimens of nickel-chromium alloy (Metal 4all, Ivoclar, USA) in 30X15X1mm3 dimension were treated using tooth brushing simulation machine (wear test machine, pin on plate unidirectional movement type) and toothpaste (modification of Balsam formula). The brushing durations were 30.9, 77.25, 123.6, and 154.5 hours as the simulation of 2, 5, 8, and 10 years tooth brushing. Surface roughness and weight difference as abrasion indicator were measured and analyzed using one-way ANOVA followed by LSD test. Tooth brushing duration of 2, 5, 8, and 10 years increased nickel-chromium alloy surface roughness (Ra) by 0.16, 0.39, 0.43, and 0.56µm with weight loss of 8%, 15%, 23%, and 32 %, respectively. These differences were statistically significant (p <0.05). The result of LSD test showed a significant effect (p <0.05) between groups of toothbrushing duration. The increase of surface roughness affects the increase of wear volume of nickel-chromium alloy indicated by R = 0.11 for brushing duration of 2, 5, 8, and 10 years. The conclusion of this study was 10 years tooth brushing promoted wear on nickelchromium alloy, which was indicated by the increase in surface roughness and weight loss.

Evolution of wear damage in gross sliding fretting of a nitrided high-carbon high-chromium steel

Fretting wear tests were performed to examine the evolution of fretting wear damage of the nitrided high-carbon high-chromium X210CrW12 steel against GCr15 steel ball, and to identify the role of nitrides (converted carbides) in fretting wear characteristics. The nitrided layer was characterized by optical microscope (OM), scanning electron microscope (SEM), energy-dispersive spectroscopy (EDS), electron probe microanalyses (EPMA), X-ray diffraction (XRD), and microhardness analysis. The worn surfaces were evaluated by SEM, EDS and 3D optical profiler. The results indicated that the initial carbides in the nitrided layer undergone a transformation into nitrides during nitriding. The nitrided specimens showed excellent wear resistance compared to the steel balls, and their wear damage was mainly caused by the adhesive/abrasive action of oxidized particles. Coarse nitrides led to the rapid wear of steel balls, and acted as barriers against the grooving of oxidized particles. Higher loading conditions of 40 N and 80 N induced the generation of central smooth zone and W-shaped wear scar. The formation of the central smooth zone was very beneficial for reducing the wear rate and friction coefficient, thus the expected increase in wear volume with increasing applied load from 40 N to 80 N was not observed.

Dry sliding friction and wear of Al 6061 and Al 6082 alloys under different normal loads

The current research work addresses evolution of coefficient of friction over sliding distance. Friction and wear tests were conducted using pin on disk type tribometer. The stabilized friction coefficient values under normal load of 10 N and 15 N for Al 6061 were noted as 0.5 and 0.58 respectively. Corresponding friction coefficient values for Al 6082 were noted as 0.6 and 0.45 respectively. Equation to calculate wear volume was derived for cylinder on flat contact. The dominant wear mechanisms were justified with the images of the disk specimens captured using optical microscope. Increase in wear volume resulting from increase in normal load was observed for Al 6061 and Al 6082 alloys.

The Influence of Graphite Content and Milling Time on Hardness, Compressive Strength and Wear Volume of Copper - Graphite Composites Prepared Via Powder Metallurgy

Copper – graphite composites are widely used in sliding bearings and brushes due to their excellent thermal and electrical conductivities and high wear resistance. The aim of this research is to study the Influence of graphite content and milling time on hardness, compressive strength, wear volume and friction coefficient of copper - graphite composites prepared via powder metallurgy. A powder mixture containing 0,5,10,15,20 and 25 vol% graphite was milled for 1,3,5,7 and 9 hours. The milled mixture was cold pressed at 700 MPa for 30 second, followed by sintering at 900 oC for one hour. It was found through this work that increasing milling time results an appreciate increase in hardness and radial compressive strength, slight reduction in wear volume and slight increase in the coefficient of friction for all compositions except that for pure copper in which a considerable increase in wear volume and decrease in the coefficient of friction was observed. On the other hand, increasing the graphite volume fraction increases the composite hardness, till an optimum value, and decreases the radial compressive strength. A great decrease in both wear volume and coefficient of friction was observed on increasing graphite content up to 25 vol%. Finally, a graphite, cast iron chips and fireclay sintering configuration was found to be an effective procedure which minimize oxidation to levels comparative with those observed previously by sintering in argon or hydrogen atmospheres.

The Influence of the Graphite Content and Milling Time on the Hardness, Compressive Strength and Wear Volume of Copper - Graphite Composites Prepared Via Powder Metallurgy

Copper – graphite composites are widely used in sliding bearings and brushes due to their excellent thermal and electrical conductivities and high wear resistance. The aim of this research is to study the Influence of the graphite content and milling time on hardness, compressive strength, wear volume and friction coefficient of copper - graphite composites that prepared via powder metallurgy. A powder mixture containing 0,5,10,15,20 and 25 vol% graphite was milled for 1,3,5,7 and 9 hours. The milled mixture was cold pressed at 700 MPa for 30 second, followed by sintering at 900 ℃ for one hour. It was found through this work that increasing milling time results an appreciate increase in hardness and radial compressive strength. Slight reduction in wear volume and slight increase in the coefficient of friction for all compositions except that for pure copper in which a considerable increase in wear volume and decrease in the coefficient of friction was observed. On the other hand, increasing the graphite volume fraction increases the composite hardness, to reach an optimum value, and decreases the radial compressive strength. A great decrease in both wear volume and coefficient of friction was observed due to increasing the graphite content up to 25 vol%. Finally, a graphite, cast iron chips and fireclay sintering configuration was found to be an effective procedure which minimizes oxidation to levels comparative with those observed previously by sintering in argon or hydrogen atmospheres.

Tribocorrosive behaviour of low temperature plasma-nitrided PH stainless steel sliding against alumina under linear reciprocation with and without transverse oscillations

In this work, precipitation hardening (PH) stainless steel was plasma nitrided at low temperatures 400°C and 425°C for 15h. The wear and corrosion-wear behaviour of the untreated and nitrided specimens were investigated under both dry sliding and wet sliding (in 3% NaCl solution) conditions, using both one-dimensional (1D) and two-dimensional (2D) reciprocating motions. The 2D motion was realised by reciprocating the sample stage as the primary motion and at the same time reciprocating the ball (pin) holder at a high frequency and small amplitude as the secondary motion. The results show that 2D sliding has significant effects on the wear behaviour of the test specimens. Under dry condition, 2D sliding leads to a significant increase in wear volume by 70–230%. Nitriding is very effective in increasing dry sliding wear resistance of the steel under both 1D and 2D conditions, with 400°C nitriding being the most effective. Under corrosion-wear (tribocorrosion) condition in 3% NaCl solution, 2D sliding leads to a more significant drop in open circuit potential (OCP) and a more significant increase in anodic current than 1D sliding. While under 1D sliding condition, nitriding is effective in reducing material removal by tribocorrosion, under 2D sliding condition, the effectiveness of nitriding is dependent on nitriding temperature. Nitriding at 425°C results in accelerated material removal during 2D sliding in the corrosive solution. The mechanisms of material removal are discussed in terms of the structures of the nitride layers and their electrochemical response to the corrosive solution.

Effect of Lubricant with Nanodiamond Particles in Sliding Friction

This paper presents the experimental effects of lubricant with nanodiamond particles in sliding friction. In order to improve the performance of lubricants many additives are used, such as MoS₂, cadmium chloride, indium, sulfides, and phosphides. These additives are harmful to human health and to the environment, so alternatives are necessary. One such alternative is nanodiamond powder, which has a large surface area. In order to investigate the effect of nanodiamonds in lubricants under sliding friction, they are dispersed in the lubricant at a variety of concentrations (0 wt%, 0.1 wt%, 0.3 wt%, 0.5 wt%, and 1 wt%) using the matrix synthesis method. Friction and wear tests are performed according to the ASTM G99 method using a pin-on-disc tester at room temperature. The specimens used in this experiment are AISI 52100 ball bearings and AISI 1020 steel discs. During the test, lubricant mixed with nanodiamond is supplied constantly to keep the two bodies separated by a lubricant film. To maintain boundary lubrication, the speed is set to 0.18 m/s and a load of 294 N is applied to the disc through the pin. Results are recorded by using workbench software over the test duration of 10 minutes. Experimental results show that when the concentration of nanodiamond increases, the coefficient of friction decreases. However, above a nanodiamond concentration of 0.5 wt%, both the coefficient of friction and wear volume increase. From this experiment, the optimum concentration of nanodiamond showing a minimum coefficient of friction of 0.09 and minimum wear volume of 0.82 nm² was 0.5 wt%.

Is the wear coefficient dependent upon slip amplitude in fretting? Vingsbo and Söderberg revisited

More than 25 years ago, Vingsbo and Söderberg published a seminal paper regarding the mapping of behaviour in fretting contacts (O. Vingsbo, S. Söderberg, On fretting maps, Wear, 126 (1988) 131–147). In this paper, it was proposed that in the gross-slip fretting regime, the wear coefficient increased by between one and two orders of magnitude as the fretting displacement amplitude increased from around 20µm to 300µm (defined as the limits of the gross-slip regime).Since the publication of this paper, there have been many papers published in the literature regarding fretting in the gross-sliding regime where such a strong dependence of wear coefficient upon fretting displacement has not been observed, with instead, the wear coefficient being shown to be almost independent of fretting amplitude. Indeed, many researchers have demonstrated that there is a good correlation between wear volume and frictional energy dissipated in the contact for many material combinations, with the additional insight that a threshold in energy dissipated in the contact exists, below which no wear is observed (experimental data relating to fretting of a high-strength steel is presented in the current paper which supports this concept).It is argued that in deriving a wear coefficient in fretting, there are two key considerations which have not always been addressed: (i) the far-field displacement amplitude is not an adequate substitute for the slip amplitude (the former is the sum of the latter together with any elastic deformation in the system between the contact and the point at which the displacement is measured); and (ii) there is a threshold in the fretting duration, below which no wear occurs and above which the rate of increase in wear volume with increasing duration is constant (this constant may be termed the wear coefficient, ktrue). Not addressing these two issues results in the derivation of a nominal wear coefficient (knominal) which is always less than ktrue. A simple analysis is presented which indicates thatknominalktrue=1−A−Bwhere A is associated with erroneously utilising the far-field displacement amplitude in place of the contact slip amplitude in the calculation of the wear coefficient and B is associated with the failure to recognise that there is a threshold in fretting duration below which no wear occurs.A and B are shown to depend upon the tractional force required to initiate sliding (itself dependent upon the applied load and coefficient of friction), the system stiffness, the applied displacement amplitude, the threshold fretting duration below which no wear occurs and the number of fretting cycles in the test. Using typical values of these parameters, the ratio of knominal to ktrue has been shown to be strongly dependent upon the applied displacement amplitude over the range addressed by Vingsbo and Söderberg (with the ratio rapidly decreasing by an order of magnitude over this range). As such, it is argued that ktrue shows no strong dependence on slip amplitude in fretting, and that the strong dependence of knominal upon displacement amplitude presented by Vingsbo and Söderberg does not imply a change in ktrue as is often inferred.The routine recording of force–displacement loops in fretting is a major experimental advancement which has taken place since the publication of the paper by Vingsbo and Söderberg. It is argued that this technique must be routinely used to allow the correct interpretation of wear data in terms of the actual slip amplitude (or energy dissipated); moreover, a range of conditions should be experimentally examined to allow the threshold fretting duration below which no wear has occurred to be evaluated and its significance assessed.

Mechanochemical Wear of Soda Lime Silica Glass in Humid Environments

The mechanochemical wear of multicomponent glasses was studied under controlled humidity conditions using a reciprocating ball‐on‐flat tribometer. For dry conditions, the surfaces were extensively damaged by scratching for all of the glasses, while for humid conditions the wear behavior varied with the glass composition suggesting a chemical effect on scratch behaviors of glass surfaces. The wear of soda lime silica (also called sodium calcium silicate) glass was suppressed with increasing humidity, while the borosilicate and barium boroaluminosilicate glasses showed an increase in wear volume with increasing humidity. The unique humidity dependence of the observed mechanochemical wear of soda lime silica glass supports the hypothesis that hydronium ion formation in the sodium‐leached sites of the soda lime glass enhances its wear resistance.

Wear performance of SiC/G coating at elevated temperatures

To improve the wear performance of SiC materials, a SiC/graphite (SiC/G) coating was prepared by CVD. Wear tests were conducted at elevated temperatures, and related microstructure and mechanical characteristics were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and micro-hardness tester. The results show that the SiC/G coating has excellent anti-wear performance with low friction coefficient at RT owing to the lubrication of graphite. Moreover, the friction coefficient of the SiC/G coating is lower than that of the uncoated SiC samples at all tested temperatures. As the temperature rose to 250 °C, the wear mechanism of SiC/G coating was shifted to severe adhesive wear, which resulted in an increase in friction coefficient. However, fracture and oxidation dominated the friction process of SiC/G at 500 °C, which caused an increase in wear volume. In addition, the formation of silica debris was conductive to the decrease of friction coefficient.

Comparison of fretting corrosion behaviour of Ti–6Al–4V alloy and CP-Ti in Ringer’s solution

The fretting corrosion behaviour of Ti–6Al–4V alloy in Ringer’s solution was evaluated and compared with that of commercially pure titanium (CP-Ti). Free corrosion potential, morphology of the fretted zone, extent of formation and accumulation of debris and wear volume were used as parameters of evaluation. Both Ti–6Al–4V alloy and CP-Ti behave similarly in terms of change in free corrosion potential as a function of time, morphological features and wear mechanism. Ti–6Al–4V alloy, however, exhibits an increase in corrosion susceptibility, decrease in tendency for repassivation, higher amount of formation and accumulation of debris and an increase in wear volume compared with CP-Ti. The study points out the importance of material selection for implants that would encounter fretting corrosion.