Abstract: Ti-6Al-4V alloy was borided by solid state diffusion process in a solid medium by applying annealing processes at various temperatures. Boriding up to 950 ºC caused the formation of a thin TiB2 phase on the top and TiB whiskers toward the substrate. At temperatures above 950ºC, a thicker TiB2 phase developed on the top of the boride layer. Boriding at 1100 ºC increased the hardness of monolithic TiB2 layer up to 4000 Hv0.01, and the hardness decrased gradually through the TiB whisker and finally reached to the hardness of base material. Boriding of Ti-6Al-4V alloy at 1100 ºC improved substantially its wear resistance under all applied loads from 7 N to 32 N. No considerable wear volume occurred on the borided Ti samples up to 17 N load, above which limited spalling or delamination were observed in wear tracks of borided sample due to the result of fatigue wear of boride layer. The improved wear resistance of borided samples is attributed to the strong and adhered borided layer. Rockwell-C adhesion nand scratch tests also showed that borided layer has sufficient adherence to substrate of Ti-6Al-4V alloy sample due to the TiB whiskers that behaves as a joint between top monolithic layer and substrate.
Keywords: Ti-6Al-4V, Boriding, Wear, Microstructure, Hardness
