Current Status and Trends in Duplex Surface Engineering of Titanium Alloys

It is known that neither thin coatings nor deep hardening through surface alloying can provide a titanium surface with combined improvements in load bearing capacity and tribological compatibility. However, many challenging complex design situations have in recent years, emerged where the combination of several properties (such as high specific strength, high wear resistance and load bearing capacity) are required. These new challenges can be met only through realising the potential of duplex surface engineering of titanium alloys. To this end, one of the focuses of surface engineering research at University of Birmingham in recent years has been duplex surface engineering of titanium alloys. In this paper, the necessity and characteristics of duplex surface engineering of titanium alloys are first discussed. By way of example, progress in the surface engineering of titanium alloys is then overviewed, including such duplex systems as PVD TiN coating/plasma nitriding, electron beam alloying/plasma nitriding, oxygen diffusion/DLC coating, and oxygen diffusion/oxide layer. Then, the importance of contact mechanics modelling in the development of duplex surface systems is demonstrated. Finally, future research directions are discussed and identified.