Numerical analysis of the strength of polycrystalline diamond as a function of microstructure

Abstract

Developing an understanding of the dominant failure mechanisms, and identifying the underlying structure–property relationship for polycrystalline diamond (PCD) are of fundamental importance for establishing a roadmap for the future design of materials with improved properties. In this paper, the Finite Volume (FV) method is used to generate representative PCD microstructures based on a diffuse-interface modelling approach. A cell-centred arbitrary crack propagation model is adopted to explore the strength and failure distribution of PCD as a function of the underlying microstructure. In particular, simulations are undertaken to identify the influence of phase morphology and individual constituent properties on the overall fracture strength of PCD. Results indicate that the morphology and distribution of the second phase cobalt relative to grain boundaries have a significant influence on the fracture strength of PCD. The stochastic nature of the strength of the individual grain boundaries was investigated. Larger variation in the distribution of interfacial bond strengths was found to result in a decrease in the overall strength for PCD grades. The effect of removing the cobalt from the microstructure was such that it reduced the overall strength but elevated the sensitivity to grain bond strength distribution. The presented work provides a framework for identifying the salient microstructural features, and offers a means for developing future grades of PCD through targeted virtual material design.