Plasma spraying process parameters greatly affect the coatings crystallinity since they can change the torch enthalpy, causing substantial melting of the particles and also affecting their cooling and solidification processes. In this work, the effect of the process parameters - current, proportion of primary/secondary gases and distance torch-substrate - on the crystallinity of hydroxyapatite coatings were evaluated. The experiments were carried out using a complete factorial design, with three parameters in two levels. The hydroxyapatite powder used was from Calcitek-USA. The crystallinity index was determined based on a quantitative procedure using the x-ray diffraction spectra. The process parameter which had the major effect on the crystallinity was the spray distance. The crystallinity index measured varied between 20-68% for the different coating conditions. Heat treatment of the coatings increased the index to 99%.
plasma spray; hydroxyapatite; coatings
