Novel Bioactive Composites by Thermal Spray Process

Hydroxyapatite (HA) is increasingly being designed to restore body function and to facilitate healing. HA coating on Ti-6Al-4V alloy is a common implant being used in orthopaedic applications. However, HA coatings prepared by plasma spraying often show low load bearing capacity and the tendency to cracking and fracture. Therefore, to bridge the gap in biomaterials with HA having low load bearing characteristics, bioceramic composite coatings are being developed. Two different kinds of HA composite coatings are being studied, namely HA/Ti-6Al-4V and HA/YSZ (Yttria-Stabilized Zirconia). HA combined with non-toxicity and bioinert Ti-6Al-4V provides an implant that is biocompatible, light and stable. Likewise, HA combined with biocompatible Y-ZrO₂ gives an implant that is favorable in its strength and fracture toughness. In this paper, the microstructure, mechanical properties, bioactivity and biocompatibility of the composite coatings were investigated. The study was also designed to evaluate the in vitro and in vivo response of HA/Ti-6Al-4V composite coatings. Tensile adhesion test and indentation tests showed a better mechanical properties for the composite coatings compared to pure HA coatings. Results also showed that the HA/Ti-6Al-4V composite coating has a sufficient mechanical strength and a good affinity to tissues of living bodies, which is useful for implants in living bodies.