Microstructure and tribological characteristics of Ti–6Al–4V alloy against GCr15 under high speed and dry sliding

The dry sliding friction and wear characteristics of Ti–6Al–4V alloys against GCr15 steel were investigated on a high speed pin-on-disc tribometer. Their microstructure changes on sliding surface and subsurface were examined by using scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that the temperature of β phase transformation for Ti–6Al–4V is closely related to that of turning point of friction coefficient and wear rate. The oxides are formed in the order of TiO, TiO2 and V2O3 with the frictional temperature increasing. TEM analysis denotes that the poly-crystals are separated out on the subsurface of Ti–6Al–4V alloys because of the rapid temperature shift. The high frictional temperature promotes the penetration of nitrogen in air to the surface and causes the formation of VN. The above results reveal that microstructure changes due to friction heat are largely responsible for the differences in the tribological characteristics.