Microstructure and formation mechanism of titanium matrix composites coating on Ti-6Al-4V by laser cladding

Laser cladding experiments were done on a 5-kW continuous wave CO 2 laser to synthesize TiC and TiB reinforced titanium matrix composite coatings on Ti-6Al-4V alloy with a mixture of Ti and B 4C precursor powder. The thermodynamics of the reactions were calculated and analyzed. The microstructure and phase evolution of TiB and TiC composites were investigated. The results showed that the chemical reaction between Ti and B 4C would release much heat, and these compounds, TiC, TiB, and small amount of TiB 2, can be formed on the surface of Ti-6Al-4V alloy if the supplied energy is sufficient to excite the reaction among the initial products. A good metallurgical bond between the coating and the substrate can be achieved. The microhardness of coating was irregular and the maximum value was approximately HV600.