Abstract: Rotating pin-on-disc friction test were carried out at room temperature in ambient air and nitrogen gas to investigate the friction and wear behavior of WC-Co cemented carbide sliding against Ti6Al4V alloy. Scanning electron microscope(SEM) and Energy dispersive x-ray spectroscopy(EDS) were used to examine the worn surfaces of the WC-Co pin and Ti6Al4V disc.Result shows that,compared to air,nitrogen gas brings a slight decrease in coefficient of friction,but a significant reduction in wear rate of both pin and disc.SEM observation and EDS analysis indicate a distinct difference in wear mechanism between the pin and disc.Severe grooving,squeezing,adhering and tearing interactions are the main mechanisms causing the extensive wear of disc.Abrasion,adhesion and 'pulling out' are the main mechanisms resulting in the wear of pin.