Friction and wear behaviors of the PVD ZrN coated carbide in sliding wear tests and in machining processes

Abstract

Medium-frequency magnetron sputtered PVD ZrN coatings were deposited on YG6 (WC + 6 wt% Co) cemented carbide. Microstructural and fundamental properties of the ZrN coatings were examined. Sliding wear tests against hardened steel using the ring-block method and dry machining tests on hardened steel were carried out with these coated materials. The friction coefficient and wear rates were measured. The wear surface features of the coatings were examined by scanning electron microscopy. Results showed that the PVD ZrN coatings onto the cemented carbide substrate show high hardness and good adhesion with the substrate. The friction coefficient of the sliding couples increased with the applied load and the sliding distance. Failures of the ZrN coating occur down to the carbide substrate under high load conditions or with long sliding distance in sliding wear tests, and are accompanied by the extensive abrasive wear on the substrate owing to the wear debris. The ZrN coated tools showed much better cutting performance compared to the YG6 uncoated carbide, which is connected with their large hardness increase, and good abrasive wear resistance. Abrasive wear was found to be the predominant flank wear mechanism for the ZrN coated tools. While the mechanisms responsible for the rake wear were determined to be adhesion.