Mechanical and tribological behavior of nanostructured TiB2 coating on high speed steel.

Attempts have been made to fabricate the superhard coatings with the purpose to reduce the wear and to improve the tribological performance of the coatings for industrial applications. Several coatings have been produced by the use of direct current and radio frequency magnetron sputtering technique using titanium and TiB2 as material targets and high speed steel as substrate. The resultant TiB2 coatings were characterised by a variety of experimental techniques. Scanning electron microscopy (SEM) was employed for coating failure behaviour investigation. Nanoindentation and Micro-scratch were used to extract the intrinsic hardness and elastic modulus evaluation and critical load to the coating failure, respectively. Ball-on-disc sliding test under unlubricated sliding was employed for tribological measurement, for instance, friction coefficient and coating wear-life. The experimental results showed that under unlubricated sliding against an alumina ball, the TiB2 coatings produced under various deposition conditions obviously increase the wear resistance of high speed steel by more than three times but extremely excellent wear resistance with encountering steel ball.