High-temperature wear behavior of micro- and ultrananocrystalline diamond films against titanium alloy

In the present study, we conducted tribological experiments to study the wear behavior of micro- (MCD) and ultrananocrystalline diamond (UNCD) films against titanium alloy at temperatures up to 700 degrees C. We found that at comparatively low temperatures (25-500 degrees C), the wear of diamond films is basically induced by the strong adhesion between diamond and titanium, which promotes the formation of Ti-C bonds and detaches the carbon atoms from the diamond surface. When the temperature increases to 600 degrees C, oxygen starts to significantly etch the diamond films, producing gaseous CO/CO2 and causing more loss of carbon atoms. At 700 degrees C, the UNCD film is systematically etched by oxygen, and the film is dominated by WO3, with drastically decreased wear resistance. The MCD film still maintains certain wear resistance at 700 degrees C, but it is also severely etched by oxygen, with substantially shrunk MCD grains. This work provides significant insights into the high-temperature wear behavior of diamond films and the application of diamond-coated cutting tools for machining titanium alloy and other high-cutting-temperature materials.