| In the present work, attempts have been made to fabricate the multilayered ultrahard coatings using sputtering technique, with the purpose to reduce the wear and to improve the tribological performance of the films for manufacturing applications. Several films 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 films were characterised by a variety of experimental and analytical techniques. Field emission scanning electron microscopy was used for film morphology and fractured cross-section examination. Nanoindentation was used to extract the intrinsic hardness and elastic modulus evaluation. Ball-on-disc sliding test under unlubricated sliding was employed for tribological measurement, for instance, friction coefficient and film wear-life. The experimental results showed that the multilayered TiB2 ultrahard coatings express high hardness and good coating adhesion. The enhanced adhesion is due to the technique of layering the hard layer with the tougher material as called multilayer structure. Under unlubricated sliding against an alumina ball, the TiB2 multilayered ultrahard coatings produced under various deposition conditions increases the wear resistance of high speed steel by more than three times but extremely excellent wear resistance with encountering steel ball. It is noted that all samples can improve the wear resistance of high-speed steel. The multilayered TiB2 ultrahard coatings provides a hard layer to resist plastic deformation and eliminate adhesion between the test surface and the ball slider, which are the main reasons of severe wear of untreated high speed steel. |
full paper (pdf, 1264 Kb)