Microstructure and crystallinity in hydroxyapatite coatings.

Plasma spraying was used to produce hydroxyapatite (HA) coatings on metal. The microstructure of these coatings, sprayed with two powder particle size distributions, was examined by scanning electron microscopy (SEM) and showed scattered HA particles with completely melted and unmelted or partially melted cores. Röntgen diffraction shows that the crystallinity increases after a vacuum heat treatment at 600 degrees C. SEM reveals that the amorphous phase recrystallized and new crystalline grains were formed at the surface of the crystalline cores.