National Physical Laboratory

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

Mingard, K P, Jones, H G, Gee, M G, Roebuck, B, Nunn, J W
Int. J. Refrac. Met. Hard Mat., 2013, 36, 136-142
NPL Doc. Ref:
PDB: 6613 | DDB: 5218
Document Type:
Periodical article

Note: An asterisk after an author's name indicates a non-NPL author.


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 has been used to characterise the effects of microstructure and crystallography 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 earlier work, 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.

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