Development of Hydroxyapatite Coating by Microplasma Spraying

Bioactive hydroxyapatite (HAP) coating (Ca/P-1.67) was developed on surgical grade SS316L substrate using the microplasma spraying (MIPS) process with low (1.5kW) plasmatron power. The MIPS-HAP coating showed both crystallinity and volume percent open porosity much higher than those usually reported for HAP coating deposited by the conventional macroplasma spraying (MAPS) process with high plasmatron power. The X-ray diffraction (XRD) data identified the coating to be nearly phase pure. The Fourier transformed infrared (FTIR) data suggested that a process of dehydroxylation and rehydroxylation might have occurred in the as-sprayed and post-heat treated coatings, respectively. The coating had a highly heterogeneous microstructure comprising of splats, completely and/or partially molten and unmelted splats retaining a nonflattened core, micropres, macropres, inter-, and intrasplat cracks.