Characteristics of Crystal Structure and Biodegradablity of Titanium-Based Ca-P Coatings

Two calcium and phosphate (Ca-P) coatings with special topographies were prepared on the pure titanium substrates by air plasma spraying. The microstructures and composition of the two special crystals were analyzed by SEM and EPMA. The phase compositions and crystallinty of coatings were quantitatively investigated by XRD. The results show that a lot of square prismatic-like dicalcium phosphates (Ca2P2O7) crystals with 4.61% crystallinity were formed under 22 kW spraying power and 400 mm/s rate of gun movement; and a large number of petal-like tetracalcium phosphate (Ca4P2O9) crystals with 6.02% crystallinity were formed under 26 kW spraying power and 300 mm/s rate of gun movement. As a result of the small particle size of the spaying powder, the HA has a low degree of crystallinity in both two coatings. In addition, the study of biodegradation shows that the processes of degradation of the two coatings proceed from fiercely to gently, but the degradation rate of the former is lower than that of the latter.