Characteristics and wear performance of borided Ti6Al4V alloy

In this study, a 10 µm thick uniform boride layer, composed of TiB2 and TiB phases, was formed on the surface of a Ti6Al4V alloy using a pack boriding technique. The hardness of the boride layer was over 2000 HV. Beneath the boride layer, a boron diffusion zone (BDZ) appeared with a thickness of about 50 µm. The microstructure of the BDZ was composed of randomly oriented TiB whiskers mixed with the structure of the base metal. In the BDZ, hardness decreased gradually towards the base metal owing to the reduction of the TiB volume fraction. The borided alloy exhibited excellent wear resistance along with a lower coefficient of friction against sapphire ball under both dry and smear lubricated sliding conditions when compared to the as-received state.