In situ observation of crack growth in a WC-Co hardmetal and characterisation of crack growth morphologies by EBSD

Controlled crack growth in a WC-Co hardmetal has been observed in-situ in the SEM using an ultra-stiff test rig to allow controlled application and removal of loads. Cracks were observed to propagate in jumps of between 20 μm and 70 μm with each jump occurring in less than 200 ms. High resolution SEM images and EBSD mapping have been used to characterise the effects of microstructure and WC grain orientation on the crack path and the degree of plastic deformation in both binder and carbide phases. The fracture in the hardmetal grade examined is dominated by transgranular fracture of the carbide phase with increased plastic deformation in grains fracturing on {10–10} planes observed by EBSD. At variance with some published research, plastic deformation in the Co binder phase ahead of the crack tip has been observed over distances of several times the Co mean free path.

► In situ controlled crack growth in WC-Co seen in SEM.
► Crack path crystallography and plastic deformation in binder and carbide mapped with EBSD.
► Transgranular fracture seen on {10–10} planes.
► Plastic deformation several times the Co mean free path seen ahead of the crack tip.