Wear Behavior of Plasma Spray Deposited and Post Heat-Treated Hydroxyapatite (HA)-Based Composite Coating on Titanium Alloy (Ti-6Al-4V) Substrate

The present study concerns a detailed evaluation of wear resistance property of plasma spray deposited composite hydroxyapatite (HA)-based (HA-50 wt pct TiO₂ and HA-10 wt pct ZrO₂) bioactive coatings developed on Ti-6Al-4V substrate and studying the effect of heat treatment on it. Heat treatment of plasma spray deposited samples has been carried out at 650 °C for 2 hours (for HA-50 wt pct TiO₂ coating) and at 750 °C for 2 hours (for HA-10 wt pct ZrO₂ coating). There is significant deterioration in wear resistance for HA-50 wt pctTiO₂ coating and a marginal deterioration in wear resistance for HA-10 wt pct ZrO₂ coating in as-sprayed state (as compared to as-received Ti-6Al-4V) which is, however, improved after heat treatment. The coefficient of friction is marginally increased for both HA-50 wt pct TiO₂ and HA-10 wt pct ZrO₂ coatings in as-sprayed condition as compared to Ti-6Al-4V substrate. However, coefficient of friction is decreased for both HA-50 wt pct TiO₂ and HA-10 wt pct ZrO₂ coatings after heat-treated condition as compared to Ti-6Al-4V substrate. The maximum improvement in wear resistance property is, however, observed for HA-10 wt pct ZrO₂ sample after heat treatment. The mechanism of wear has been investigated.