Mechanical properties of vacuum plasma sprayed reinforced hydroxyapatite coatings on Ti-6Al-4V alloy

The aim of this present work was to deposit reinforced hydroxyapatite coatings with a bond coat of zirconia on Ti-6Al-4V substrate using the vacuum plasma spray technique in order to improve the surface properties. To achieve that, HA + 10 wt% Al2O3 and HA + 10 wt% ZrO2 coatings with an intermediate layer of zirconia were deposited on Ti-6Al-4V implant substrate. Further, these coatings were subjected to post-coating heat treatment at 700 °C for 1 h. The morphology and phase analysis of bio-ceramic powders, as-sprayed and heat-treated coatings, have been characterized using a scanning electron microscope and an X-ray diffractrometer. Crystallinity, surface roughness, porosity, hardness and shear strength were also investigated. The wear behaviour of the coatings was evaluated using a Taber abrasion tester as per ASTM F1978 standard. The results indicate that heat-treated coatings exhibit lower wear resistance than as-sprayed coatings and show lower porosity and higher crystallinity and hardness after heat treatment. Slight improvement in shear strength was observed after heat treatment.