Molecular Dynamics Simulations of Grain Boundaries in Cemented Carbides

Abstract

Cemented carbide is a tool material used in metal machining in industry. It is a composite material based on a mixture of a hard carbide phase and a more though metal binder phase. When used in cutting applications, the productivity is often limited by high temperature plastic deformation. A suggested mechanism for this deformation is grain boundary sliding and separation. In the present thesis grain boundary sliding and separation are studied for the tungsten carbide (WC) { cobalt (Co) system. Clean WC/WC grain boundaries and WC/WC grain boundaries with half a monolayer of segregated Co is investigated. The simulation method used in the thesis is molecular dynamics using a three body analytical bond order potential. The grain boundary sliding and separation was performed using a constant strain rate. The stresses under sliding and separation were found to be on the order of 1{10GPa. Furthermore, other studies have shown that the stresses are substantially reduced for grain boundaries with several layers of Co, i.e. thin films of Co. The occurrence of grain boundaries with thin films of Co is therefore likely to be crucial for the plastic deformation in WC{Co.