Abstract: Hydroxyapatite (HA) coatings on Ti-6Al-4V substrate were prepared by atmospheric plasma spraying method under a variety of
spray distances and spray powers. The structure of HA coatings were then studied by Scanning Electron Microscopy (SEM), and X-ray
Diffractometer (XRD) was applied to determine the phase composition of the coatings. The Ca/P mole ratios of the coatings were examined
by X-ray Fluoroscopy (XRF). Experimental results indicated that with the increase of spray distance, the melting state of the HA coating
was improved but the crystallinity of coating was reduced. However, the surface images and crystallinity of coatings were not influenced
by spray power significantly. The Ca/P ratio showed a higher value at shorter spray distance but increased with increase in spray power.

Key words: HA coating, plasma spraying, spray distance, spray power, Ca/P mole ratio