Microstructural characterization of TIG surface treating in Co-Cr-Mo-C alloy

The aim of the present study is to investigate the effect of surface melting using tungsten inert gas (TIG) welding process and rapid solidification on the microstructure and hardness of Ni-free biomedical Co-28Cr-5Mo-0.3%C alloy. The microstructural studies revealed that surface melting via TIG welding process results in uniform distribution of the nano-sized M23C6 carbides in the range of 10-100 nm at γ-fcc/ε-hcp interface. It was found that the volume fraction of the athermal martensite plays a key role on the size of the finely dispersed nano-sized M23C6 carbides at γ-fcc/ε-hcp interface. The hardness of TIG-treated surface was found to be greater than as-cast alloy which could be attributed to the dispersion of the nano-sized carbides at γ-fcc/ε-hcp interface as well as higher volume fraction of athermal martensite.