Corrosion damage in WC–Co cemented carbides: residual strength assessment and 3D FIB-FESEM tomography characterisation

Abstract

The effect of corrosion damage on cemented carbides was investigated. The study included residual strength assessment and detailed fractographic inspection of corroded specimens as well as detailed 3D FIB-FESEM tomography characterisation. Experimental results point out a strong strength decrease associated with localised corrosion damage, i.e. corrosion pits acting as stress raisers, concentrated in the binder phase. These pits exhibit a variable and partial interconnectivity, as a function of depth from the surface, and are the result of heterogeneous dissolution of the metallic phase, specifically at the corrosion front. However, as corrosion advances the ratio between pit depth and thickness of damaged layer decreases. Thus, stress concentration effect ascribed to corrosion pits gets geometrically lessened, damage becomes effectively homogenised and relatively changes in residual strength as exposure time gets longer are found to be less pronounced.

Keywords:

• Corrosion
• Cemented carbides
• Residual strength
• FIB Tomography

Acknowledgements

This work was financially supported by the Spanish Ministerio de Economía y Competitividad (grant no. MAT2012-34602). The support received from Direcció General de Recerca del Comissionat per a Universitats i Recerca de la Generalitat de Catalunya through recognition of CIEFMA as Grup de Recerca Consolidat 2014SGR130 is also acknowledged. Additionally, J.M. Tarragó and Joan Josep Roa would like to acknowledge financial support received from the collaborative Industry-University program between Sandvik Hyperion and Universitat Politècnica de Catalunya (PhD scholarship) and the Juan de la Cierva Programme respectively.