In-service Catastrophic Failure: or Controlling the Grain Boundary Network Evolution

Hardmetal tools are a key for our production industries relying on cutting, milling, drilling, and turning. Cemented carbides (WC-Co) are one of the most prominent powder metallurgy processed materials use for cutting tool applications. This is due to a combination of excellent hardness/wear resistance and toughness with low cost compared to alternatives such as polycrystalline diamond. During service (e.g. in machining) , however, the composite structure is subjected to a combination of high mechanical and thermal loads, where hard carbide particles are joint by soft cobalt binder, deforms until excessive wear and fracture reduce the performance and lifetime. Crack paths in WC-Co predominantly follow WC/WC and WC/Co grain and phase boundaries at low cobalt concentrations1. While the WC grain boundary character, the grain boundary network, is characterised for differently doped cemented carbides2-5, knowledge of how the grain boundary network evolves during service and ultimately allows for crack formation along grain boundaries is absent.