Triode plasma diffusion treatment of titanium alloys

► We study the tribological performance of diffusion-treated Ti-6Al-4V and Ti-15Mo. ► Oxygen and nitrogen can be used to enhance load-bearing capacity for PVD coating. ► A thin PVD Ti layer can be used to inhibit excessive surface roughening of Ti-15Mo. ► TPO treatments appear to be significantly superior to TPN in the case of Ti-15Mo.