Further studies on the effect of stand-off distance on characteristics of plasma sprayed hydroxyapatite coating

Plasma spraying parameters are of crucial importance to the fabrication of high-quality hydroxyapatite (HA) coating for biomedical use. In the present work, an HA powder finer than that commonly used was plasma sprayed onto titanium substrate. The microstructures and the phase composition of the coatings were characterized using scanning electron microscopy and X-ray diffraction, respectively. Results have shown that the extent of melting of particles decreased, while the crystallinity of the HA increased with increasing stand-off distance with power level of 40 kW. The reason was suggested to be that the molten particles began to cool and resolidify when the stand-off distance exceed a certain value.