Characterization and mechanical behaviour of reinforced hydroxyapatite coatings deposited by vacuum plasma spray on SS-316L alloy

Hydroxyapatite powder reinforced individually with 10 wt percentage (wt%) of Al2O3 and ZrO2 (HA + 10 wt% Al2O3 and HA + 10 wt% ZrO2) was thermally sprayed onto SS-316L substrate with a bond coat of Zirconia by vacuum plasma spray (VPS) technique. The resulted coatings were heat treated at 700 degrees C for 1 h to study its effects on microstructural and mechanical properties of the deposited coatings. The characterization of the coatings was carried out using scanning electron microscope, x-ray diffraction, porosity, surface roughness and crystallinity using Rietveld analysis. The results indicated that after post coating heat treatment substantial decrease in porosity was witnessed along with significant improvement in crystallinity. Besides, the hardness across the cross-section of the coatings and bond strength was considerably improved; however the hardness of top coat was reduced owing to the loosening of un-melted and partially melted particles by diffusion process which takes place during heat treatment.