Multi-scale Modeling of WC-Co Drill Bits Material with Density Functional Theory and Crystal Elasticity Model☆

Abstract A sequential method is proposed to investigate the influence of material parameters identified at different scales (atomic, grains and phase) on fracture properties of tungsten carbide-cobalt (WC-Co) drill bit material used for hard rock drilling. The study includes four commercial WC-Co grades. The representative volume element (RVE) approach was used to account for microstructural features such as volume fraction and distribution of the phases and average size of grain. Different RVEs representing the grades materials were generated and implemented in a FE model incorporating the anisotropic elastic response of the constitute grains. Brittle fracture is assumed in the phases and an energy based failure criterion using the work of separation for the WC/WC, WC/Co and Co/Co interfaces has been identified using the density functional theory (DFT). This criterion was implemented in the finite element model to determine fracture strength for the investigated grades. The elastic properties and fracture strength predicted by the model were discussed with respect to the influence of volume fraction of the phases and average grain size in the investigated WC-Co grades.