The influence of Ru additions on the corrosion behaviour of WC-Co cemented carbide in corrosive media

Abstract

The aim of the study is to investigate the influence of Ru additions on the corrosion behaviour of WC-Co cemented carbides when exposed in corrosive media. The study involved the characterisation of the microstructures, morphologies and phases present by using the optical microscopy, SEM, XRD and Raman spectroscopy before and after corrosion. The corrosion behaviour was investigated using the electrochemical polarization tests in 1M hydrochloric acid, 1M sodium chloride and synthetic mine water solutions. Three types of corrosion tests were done on the samples by electrochemical techniques: potential versus time test, potentiodynamic polarisation scans and chronoamperometry. Ruthenium affects c in 1M H2SO4 and synthetic mine water, but not really in NaCl solution. It was also observed that the passivity range and corrosion resistance decreases in order of synthetic mine water> sodium chloride> sulphuric acid. It also appears that Ru is more effective in improving corrosion resistance in all the solutions than a small vanadium carbide addition. Therefore, ruthenium additions of up to 3 wt% Ru of the WC-10%Co alloy increased the corrosion resistance of the WC-Co alloys. This is attributed to the stabilization of the cobalt fcc phase due to ruthenium additions while hcp phase is obtained when there is no ruthenium additions.