A study of the reciprocating-sliding wear performance of plasma surface treated titanium alloy

Abstract

a b s t r a c tTriode plasma nitriding was used in conjunction with electron-beam plasma-assisted physical vapour deposition of TiN and CrAlN to enhance the wear resistance of Ti-6Al-4V titanium alloy. Linear reciprocating-sliding ball-on-plate wear tests were performed to assess the tribological performance of the treated alloy. Wear volumes were correlated to changes in coefficient of friction, which is often indicative of breakdown of the surface treatment. Debris generated during wear testing was characterised using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and laser diffraction for particle size analysis. Surface micro-profilometry and SEM were used to characterise the wear scars. The results obtained indicate that, in order to assess the relative improvement in wear behaviour attained by using surface treatments it is insufficient to compare linear wear rates alone. A clear comparison is only possible if testing is carried out in steps of increasing sliding distance, until the treated/deposited layers have been completely removed. Also, it is shown that the number of repeated tests necessary to evaluate clearly the treatment and/or coating can vary substantially, depending on the observed test progression; typically this necessitates the greatest number of repeats around the point of wear at which the ball counterface contact area is in transition from the treatment layer(s) to the substrate bulk. The inherent variability in wear performance under linear ballon-plate reciprocating-sliding is correlated to debris generation, changes in relative humidity -and the resultant wear mechanisms involved.

Tribological response of AA 2024-T3 aluminium alloy coated with a DLC duplex coating

“…The alumina ball produced a slight polishing of the surface for the load applied of 2 N, polishing which is accentuated as the normal load is increased. The shape of the wear track profile indicates debris entrainment, as well as the accumulation of the debris on top of the ball, giving rise to a more pronounced W shape as indicated by Cassara et al [42]. The mean Hertzian contact pressures for the applied normal loads of 2 N and 5 N are 0.5 and 0.7 GPa, respectively.…”

Evaluating the effects of plasma diffusion processing and duplex diffusion/PVD-coating on the fatigue performance of Ti–6Al–4V alloy

“…(i) Nitride surface compound layer thickness increases with the treatment bias voltage [9]. The coefficient of diffusion of nitrogen in TiN and Ti 2 N is at least 30 times lower than for a-Ti [19,22] and therefore the compound layer act as a diffusion barrier for further nitrogen penetration into the bulk.…”

“…(ii) Extended HV processing has been proven to create a significantly rougher surface because of increased and selective sputter etching. Rougher surfaces act as a source of hard, abrasive wear debris and thereby degrade the tribological performance [9].…”

“…As a result, surface treatments which are originally designed to improve tribological behaviour should also not reduce the fatigue strength of the base material. While the tribological behaviour of similar treatments was studied recently in [9], the following discussions are focused primarily towards the effect of such treatments on fatigue behaviour. Unfortunately, there is little work on the effect of surface engineering treatments on the fatigue performance of Ti-alloys and particularly the effect of triode plasma diffusion treatments has not yet received detailed attention.…”

A novel cold atmospheric pressure air plasma jet for peri-implantitis treatment: An <i>in vitro</i> study

“…This offers a substantial advantage over other cold plasma surface modification methods because CAPAJ could achieve much higher electron density (5×10 15 /cm 3 ). When high-energy particles and free radicals which existed in air plasma impinged on the treated titanium surface, few low-energy chemical bonds were easily broken 51) . Accordingly, the C-C chemical bond ruptured, and the active ingredient •OH from plasma was grafted on the C-bond, leading to formation of the new C-OH bond.…”