| Abstract: | Titanium-based composite coatings reinforced by in situ synthesized TiB and TiC particles between titanium and B4C were successfully fab-ricated on Ti6A14V by laser cladding. Phase constituents of the coatings were predicted by thermodynamic calculations in the Ti-B4C-Al and Ti-B-C-Al systems, respectively, and were validated well by X-ray diffraction (XRD) analysis results. Microstructural and metallographic analyses were made by scanning electron microscopy (SEM) and electron probe micro-analysis (EPMA). The results show that the coatings are mainly composed of α-Ti cellular dendrites and the eutecticum in which a large number of needle-shaped TiB and a few equiaxial TiC particles are embedded. C is enriched in α-Ti cellular dendrites and far exceeds the theoretical maximum dissolubility, owing to the extension of saturation during laser cladding. The coatings have a good metallurgical bond with the substrate due to the existence of the dilution zone, in which a great amount of lamella β-Ti grains consisting of a thin needle-shaped martensitic microstructurc are present and grow parallel to the heat flux direction; a few TiB and TiC reinforcements are observed at the boundaries of initial β-Ti grains. |
