Microstructure, composition and hardness of laser-assisted hydroxyapatite and Ti-6Al-4V composite coatings

Composite coatings made of hydroxyapatite (HA) and titanium alloy (Ti-6Al-4V) have potential biomedical applications because of their biocompatibility and bioactive characteristics. In this research, composite coating of HA and Ti-6Al-4V was prepared using the laser-assisted direct material deposition method. Surface morphology, chemical composition and mechanical properties of the composite coatings were investigated using optical and scanning electron microscopy, energy dispersive X-ray spectroscopy and Vickers microhardness tests. The results show that the microstructure, chemistry and mechanical properties of the coatings are influenced by laser power and traverse speed. The aspect ratio of the coating, the ratio of calcium and phosphorous (i.e., Ca/P) in the coating and the diffusion rate of titanium into the substrate vary with power and traverse speed. Traverse speed has more influence on surface morphology and Ca/P ratio than power. The variation in microhardness along the cross section of the heat affected zone was investigated, and the diffusion coefficient of titanium into stainless steel was estimated. The relationship between microstructural, chemical and mechanical parameters with the specific energy was established.