Effects of different distribution of residual stresses in the depth direction on cutting performance of TiAlN coated WC-10wt%Co tools in milling Ti-6Al-4V

Abstract

Based on Micro-Raman spectroscopy with the laser diameter of 400 nm, effects of different distribution of residual stresses in the depth direction on hardness and cutting performance of thin TiAlN coatings (about 4 μm) on WC-10wt%Co substrate are studied. Residual stresses distribution maps from substrate to surface of two samples are acquired with the step length of 0.4 μm. The hardness, modulus and H3/E2 respectively increase about 13.97%, 17.63% and 7.10% from Sample 1 to Sample 2. The milling experiments indicate that Sample 2 with higher compressive residual stress possesses better wear capacity and lower cutting forces than Sample 1. The reason is discussed: the deeper the crack propagates in the coating, the greater the residual compressive stress, which forces the crack to propagate along the direction of stress rather than along the cleavage plane, thus inhabiting the crack propagation along the vertical direction.