Research on the in situ fabrication of bioceramic composite coatings by laser cladding

Hydroxyapatite(HAP) has excellent osteoconductive properties. By controlling the Ca/P ratio better biphasic calcium phosphate ceramics can be produced than pure HAP ceramics. calcium pyrophosphate(beta-Ca2P2O7) is a new biodegradable ceramic material and its biological response is quite similar to HAP. Obtaining HAP and other bioactive calcium phosphate ceramic coatings has been a popular research field in the past. In our research a new bioceramic composite coating was obtained by laser cladding with pre-depositing mixed powders of CaHPO(4)(.)2H(2)O and CaCO3 directly on the metal substrate. Its main constituents are HAP and beta-Ca2P2P7. The microstructure of the coating consists of minute granular HAP that is distributed among the overlapped club-shaped or needle-like beta-Ca2P2O7. The hardness distribution in the cladding layer is even and its value is much higher than that in the Substrate. There is a bonded structure of the epitaxial planar growth between the Substrate and cladding layer, and both a typical cellular microstructure in the middle and an equiaxed microstructure at the top of the cladding layer.