Cemented carbides, often simply termed as hardmetals (WC-Co), are heterogeneous composite materials consisting of a ceramic phase embedded in a metallic binder, with the former providing hardness, wear resistance and the latter presenting toughness. Such an excellent combination of properties and enables them to be perfectly well adapted for tool applications.
After sintering, different manufacturing steps need to be applied to the hardmetal in order to achieve a finished tool which fulfills requirements of real industrial applications. Diamond wheel grinding is one of the machining processes frequently implemented by hardmetal producers for machining the as-sintered hardmetal to tools with a certain subscribed geometry.
As a result of this abrasive process, surface integrity changes will be induced, such as: surface texture, micro-cracks, residual stresses and maybe phase transformation. Consequently, such surface integrity alterations will play an important role in dictating the mechanical and tribological behaviour of the manufactured tool.
Under operation, cutting tools often suffer wear phenomena, and small quantities of material are progressively removed from the surface. In assessing the lidding contact behaviour of hard materials, scratch test is one of the most common methods among the options described in the literature.
Within the above framework, the main objective of this project is to evaluate the grinding-induced anisotropy effects in terms of damage on scratch resistance and associated failure mechanisms for a WC-13%Co hardmetal. In doing so, three different surface finish conditions are investigated: ground (G), ground plus heat-treatment (G+TT) and mirror-like polished (P). Pre-existing damage network for both G and G+TT samples has been investigated through a 3D focused ion beam (FIB) tomography technique. The sliding contact response of the different surface finished hardmetals has then be evaluated by both macro- and nanometric length scale scratch, conducted both parallel and perpendicular to the direction of the grinding grooves. Interaction of pre-existing and scratch-induced damage carefully examined though the inspection of the residual sliding track by means of FIB.
A strong anisotropy nature is found at both levels: finding induced damages and nanoscratche mechanical response.
