Inclined impact–sliding wear tests of TiN/Al2O3/TiCN coatings on cemented carbide substrates

Abstract

A chemical vapor deposition (CVD) TiN/Al2O3/TiCN coating has been commercially used as a protective coating on cemented carbide cutting tools to improve tool life and superficial quality of the workpiece. However, the CVD coating is relatively brittle and could fail due to fatigue cracking induced wear under localized contact stresses during the milling operation. Traditional coating evaluation techniques such as tribo tests, scratch tests and impact tests only involve single movement, i.e., either sliding or impacting. In the present work, the fatigue and wear behavior of the triple-layered coatings on cemented carbide substrates was investigated using a novel impact–sliding wear tester, which simulates a repetitive movement of combined impact and sliding motions between cutting tools and workpieces during interrupted milling operations. The coatings on the surface and cross-section were studied using Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) analysis. The results from the impact component showed that fatigue cracking increased for the coating on a harder substrate likely due to the lower toughness of the substrate. The results from the sliding component showed that the wear resistance of the coating decreased as the substrate was softer. The test results provided constructive knowledge in selection and development of coatings for impact and sliding involved applications.