In situ fabrication of bioceramic composite coatings by laser cladding

A bioceramic composite coating was fabricated onto AISI 316L stainless steel in situ by laser cladding with mixed powders of CaHPO4•2H2O and CaCO3 without a bonding agent. The microstructures of the mixed powders and cladding layer were investigated by scanning electron microscopy, and the compositions/phases were analyzed by electron diffraction spectroscopy and X-ray diffraction. The major phases in the coating are β-Ca2P2O7 and Ca10 (PO4)6(OH)2. The coating consists of the granular HAP that is distributed among the overlapped club-shaped β-Ca2P2O7. It is shown that there is a bonded structure of the epitaxial planar growth between the substrate and cladding layer, and there is evidently a typical cellular microstructure in the middle and an equiaxed microstructure at the top of the cladding layer. The microstructure evolution in the cladding layer was analyzed based on the ratio of temperature gradient to solidification rate (G / R) produced in laser cladding.