Liquid-phase surface melting of Ti-6Al-4V in argon and nitrogen atmospheres

In this paper, liquid-phase surface melting of Ti-6Al-V in atmospheres of argon and a mixture of argon and nitrogen was carried out using tungsten inert gas process. The microstructures of treated layers were investigated by optical microscope, scanning electron microscope, and phases formed were studied by X-ray diffraction pattern. The hardness of these layers was also evaluated using microhardness machine. The results showed that the surface hardness was enhanced from 280 HV for the untreated substrate to 600 HV for the surface-treated layer achieved by surface melting in the argon atmosphere which was due to the formation of martensite microstructures. The surface layer fabricated by surface melting in the mixed atmosphere of argon and nitrogen also resulted in formation of TiN in a martensitic matrix with a hardness of about 1000 HV.