Comparison of tribological behaviours of AlCrN and TiAlN coatings—Deposited by physical vapor deposition

Abstract

TiAlN has been one of the most extensively investigated hard coatings in laboratory as well as in real life applications. However, a new ternary nitride AlCrN with high percentage of aluminum and superior properties has become the subject of ever-increasing interest. Therefore, it is worthwhile to investigate the tribological behaviours of AlCrN versus TiAlN coatings with focus on their wear mechanism. AlCrN and TiAlN coatings were deposited on cemented carbide by the arc-physical vapor deposition. Microhardness as well as nanoindentation tests have been performed to characterize the mechanical properties of the coatings. Reciprocating sliding and ball-on-disc wear tests against 4 mm diameter Si 3N 4 balls have been performed on the CETR UMT-2 test system. The coating surfaces and wear scars were evaluated by scanning electron microscopy (SEM), energy dispersive X-ray spectrum (EDX), X-ray diffraction (XRD) and laser confocal scanning microscope (LCSM). The results showed that the AlCrN coating exhibited lower friction coefficient and wear rate than those of the TiAlN coating under same testing condition. Combination of abrasive and oxidative wear was the main wear mechanism for the AlCrN and TiAlN coatings in both types of the sliding wear tests, in which the tribo-oxidation played an important role. However, for the ball-on-disc testing, an extra thin transferring film was formed in the center area of the wear track probably due to the different wear debris behaviours as a consequence of the different relative sliding modes. The AlCrN coating presented better performance of anti-oxidation and anti-spalling as compared with the TiAlN coating.