Mechanically robust TiAlSiN coatings prepared by pulsed-DC magnetron sputtering system: Scratch response and tribological performance

In this study, scratch tests and wear tests were performed on a series of magnetron sputtered TiAlSiN coatings. These coatings varied from coarse columnar grains to fine fibrous grains in microstructure, accompanied by a gradual increase in hardness and modulus values. The analysis of the scratch results showed that the critical loads (Lc1 and Lc2) were related to the H/E* and H³/E*² values, where higher H/E* and H³/E*² led to higher critical loads. The improvement in scratch toughness might benefit from the complex cracking patterns in fine-grained coatings before coating spallation occurred. The wear performance of these TiAlSiN coatings against a ruby ball revealed that coatings with coarse columnar grains possessed better wear resistance than fine-grained coatings despite the fact that fine-grained coatings had higher H/E* and H³/E*² values. It is believed that coatings with coarse columnar grains could restrain the grain pull-out process during abrasive dry sliding. In some cases, the compact layer of wear debris on the wear track, which can provide additional load bearing capacity, is beneficial to the wear resistance of the coating.