Modelling of the damage initiation at WC/WC and WC/Co boundaries in WC-Co tool material at the microstructure scale: Application to the tool/chip contact

Abstract

In machining process, the wear of tungsten‑cobalt carbide cutting tools (WC-Co) is the result of different wear mechanisms such as abrasion, adhesion and diffusion. At the microstructure scale, the presence of microcracks in the carbide grain boundaries can be observed of the tool and in the WC/Co interfaces on the cutting surface. These microcracks are the cause of the WC-Co pull-out clusters from the cutting tool face. In this work, simulations were set up to evaluate the number of WC/WC and WC/Co interfaces that are likely to be damaged first. The behaviour of each phase was modelled by thermo-elasto-plastic behaviour and cohesive interfaces of zero thickness were used to simulate the behaviour of WC/WC and WC/Co interfaces. Different quasi-realistic microstructures were generated by an algorithm to evaluate the dispersion of the results. These microstructures are surrounded on three sides by an assumed homogeneous WC-Co embedding. The microstructure and the embedding form a part of the cutting tool with one side rubbing against a rigid chip to locally reproduce the chip/tool contact. The results of this study show the influence of the cobalt content, temperature, friction coefficient and orientation of the interfaces on the number of interfaces likely to be damaged first.