Apatite/titanium composite coatings on titanium or titanium alloy by RF plasma-spraying process

To improve adhesiveness of hydroxapatite (HA) coatings to the titanium substrates, a HA/Ti composite was formed on substrates using a radio-frequency (RF) plasma spraying process. This process would reduce the residual stress caused by the large difference between the linear thermal expansion coefficient of the substrate and of HA. The HA/Ti composites were prepared by controlled feeding ratio of HA and Ti powder, with the composition of coatings becoming HA-rich toward the outer surface. Coating layers were evaluated by SEM-EDX, XRD, micro FT-IR and tensile testing. Orientation in c-axis direction of the prepared coatings was established from X-ray diffraction patterns. The adhesive (tensile) strength of HA/Ti composite coatings was approximately 50 MPa. The adhesiveness of the HA/Ti composite coatings was increased with increasing the inductive power of plasma.