Toughening and fatigue micromechanisms in hardmetals: FESEM/FIB tomography characterization

The particular microstructure assemblage of hardmetals yields those materials an extraordinary combination of hardness and toughness. On the other hand, it is also known that these materials are prone to strength degradation under cyclic mechanical loads. Within this context, the metallic binder phase plays a key role as the toughening and fatigue susceptible agent in cemented carbides, as its effective ductility is critical for defining crack shielding effects and cyclic induced degradation. However, experimental proof of involved toughening and fatigue micromechanisms has usually been presented in the literature on the basis of post-failure fractographic examination. In this work, a detailed characterization of crack-microstructure interaction during stable crack growth in hardmetals is attempted. In doing so, FESEM/FIB tomography is combined with systematic mechanical and indentation testing protocols (under monotonic and cyclic loads) for assessing crack extension behavior of hardmetals. The study clearly highlights existing differences regarding failure micromechanisms operative under monotonic and cyclic loads