Microstructure and surface mechanical properties of plasma spray deposited and post spray heat treated hydroxyapatite (HA) based composite coating on titanium alloy (Ti-6A1-4V) substrate

摘要

The present study concerns a detailed microstructural characterization and evaluation of surface mechanical properties of the plasma spray deposited hydroxyapatite (HA) based (HA + 50 wt% TiO2 and HA + 10 wt% ZrO2) composite coatings on Ti-6A1-4V substrate and studying the effect of heat treatment on it. Heat treatment of plasma spray deposited sample has been carried out at 650 degrees C for 2 h (for HA + 50 wt% TiO2 coating) and at 750 degrees C for 2 h (for HA + 10 wt% ZrO2 coating). The microstructure of the as-sprayed coating shows the presence of porosities and un-melted particles on the surface, the area fraction of which is reduced after heat treatment. There is an improvement in hardness after heat treatment from 2.15 GPa to 2.2 GPa in HA + 50 wt% TiO2 coating and from 1.1 GPa to 2.3 GPa in HA + 10 wt% ZrO2 coating. There is a marginal enhancement in the Young's modulus from 78 GPa (in as-sprayed coating) to 80 GPa (due to post heat treatment) in HA + 50 wt% TiO2 coating and from 55 GPa (in as-sprayed coating) to 70 GPa (due to post heat treatment) in HA + 10 wt% ZrO2 coating.