Influence of cryo-processing on properties of tungsten carbide with low, medium and high cobalt content

Abstract

This research was designed to evaluate the influence of cryo-processing on properties of tungsten carbide with varied cobalt content. Samples of uncoated tungsten carbide with 6% (WC-6 wt%Co), 9% (WC-9 wt%Co) and 25% cobalt (WC-25 wt%Co) content were fabricated for the research. Magnetic properties, porosity analysis, eta phase analysis by microscopic observation, EDS, XRD and Vickers hardness were evaluated. Investigation shows that 25% cobalt content samples after cryo-processing exhibit a significant improvement of around 2.2% in Vickers hardness and 8.7% in coercivity followed by samples with 9% cobalt grade (1.2% increase in Vickers hardness and 2.1% in coercivity), whereas 6% cobalt samples showed negligible changes. There is no change in the other properties in any of the selected grades. The change in Vickers hardness and coercivity are attributed to the cobalt’s phase transformation from FCC to HCP structure in cryo-processed samples. This study reveals that the amount of cobalt used in the fabrication of tungsten carbide tools is the determinant factor for the changes in properties.