Characterization of Thermal Sprayed Hydroxyapatite Coatings on Some Biomedical Implant Materials

Purpose To characterize two thermal sprayed coatings of different particle-sized hydroxyapatite on some biomedical implant materials. Methods Characterization of the as-sprayed coatings was performed using x-ray diffractometer, scanning electron microscopy/energy dispersive spectroscopy, and x-ray mapping techniques. Bond strength of the sprayed coatings measured as per ASTM-C633 standard and cell culture studies were performed to assess the biocompatibility of the coatings. Results The results indicated that, HA coatings of 10 μm particle sized powder were completely amorphous, while that of 30 μm sized powder consisted of crystalline HA with minor tetracalcium phosphate and tricalcium phosphate phases. This flame spray HA-A and HA-B coatings exhibited higher bond strength (67.8 and 49.3 MPa respectively) in comparison with other thermal spray HA coating techniques reported in literature. In vitro biocompatibility studies revealed that HA-B coated specimens had good biocompatibility with a human osteosarcoma cell line KHOSNP (R-970-5). Conclusions These observations show that particle size of HA powders have a significant effect on the phase composition, microstructure, roughness and biocompatibility of deposited coatings. HA-B coatings were found to be metallurgically better than the HA-A coating from the point of view of biomedical applications.