Assessment of irreversible deformation and cracking behavior of WC-Co cemented carbides by means of blunt indentation

The combined resistance against irreversible deformation and cracking is key for the functional performance of hard and brittle-like materials. In this work, it is studied in WC-Co hardmetals by means of blunt (spherical and conical) indentation, as this allows the simultaneous evaluation of elastic-plastic deformation and damage evolution. Within this context, the ratio between the critical loads associated with the onsets of yielding ( P y ) and initiation of ring / radial cracks ( P c ) under spherical and conical indentation, is validated as a meaningful definition of brittleness index. This statement is supported by the microstructural influence trend determined using the referred P y / P c ratio for describing the deformation-fracture compromise of the materials under consideration. Concurrently, the cracking evolution, beyond the emergence of the first fissure, is documented through contact damage maps. The collected data are then used to determine crack growth resistance ( W ) linked to axis-symmetric radial fissures under conical indentation. Direct comparison with phenomena taking place under sharp indentation, where similar radial Palmqvist cracks develop, permits to analyze and validate such a testing procedure for assessment of W ; and thus, correlate it with the fracture toughness of the hardmetals studied. Following the results here presented, blunt indentation comes out as an interesting approach not only to quantify brittleness in cemented carbides, but also to evaluate surface integrity changes induced under service-like conditions.