In-situ TiC-TiB2 coating on Ti-6Al-4V alloy by tungsten inert gas (TIG) cladding method: Part-I. Microstructure evolution

In order to improve the surface mechanical performance of Ti-6Al-4V alloy, in-situ TiC-TiB2 composite coating was deposited by tungsten inert gas (TIG) cladding process using Ti and B4C as precursor powder. Based on the available literature, SEM images of the blended precursor powder mixture and coating layer, electron probe micro analysis (EPMA) and corresponding XRD analysis of the produced coating, the formation mechanism of the present TiC-TiB2 composite coating during TIG cladding process was elucidated. The analysis shows that in the coating, TiB2 and TiB phases appeared as hexagonal or rectangular shape, whereas TiC as spherical shape within the matrix of unreacted Ti, Ti-6Al-4V alloy form the substrate and intermetallic phase like TiAl3 formed during the cladding process. The analysis also revealed that the TIG cladding processing current and scan speed have substantial effect on the coating morphology and the phases formed in the coating.