Fracture and fatigue behavior of a γ-phase containing WC-Co cemented carbide

Abstract

This study analyzes the microstructural effects of a third phase on fracture and fatigue characteristics of WC-based cemented carbides. A γ-phase-containing (three-phase) hardmetal grade is investigated and compared to a reference two-phase system, with similar binder content and WC grain size. Isolation of the mixed cubic carbides (third phase) out of the binder plays a key role on determining the fracture and fatigue characteristics. Consequently, coarser microstructural heterogeneities are found acting as critical flaws, decreasing strength, under both monotonic and cyclic loading. Conversely, γ-phase promotes a ceramic-like transgranular crack path for stable crack extension under cyclic loading, yielding lower fatigue sensitivity. Fatigue mechanics and mechanisms of the γ-phase grade align with those of WC-Co systems, independent of crack size. The combined use of pristine and pre-cracked specimens effectively correlates strength, fracture toughness, and fatigue life with estimated and experimentally determined fatigue crack growth exhibited by natural and long through-thickness cracks.