Abstract
The tribological behaviour of WC-Co-Cr coatings deposited by HVOF and HVAF and WC-Co coating deposited by HVAF was investigated in pin-on-disc tests. Wear rates were determined and wear tracks on the coatings and counterbodies were investigated in SEM. The HVAF sprayed coatings showed greater wear resistance compared to the HVOF coatings. The main wear mechanism in the WC-Co coatings was adhesive wear. The cobalt matrix is lubricious, resulting in very low wear rates and low debris generation. The main wear mechanisms in the WC-Co-Cr coatings were adhesive and abrasive wear. Adhesive wear results in pull-outs that are trapped in the contact zone and act as a third-body abrasive. Particle pull-out of the coating significantly increases the wear rate of the coated specimen. The HVAF WC-Co-Cr coatings proved to have a better resistance to particle pull-out which reflected in a considerably lower wear rate than the HVOF WC-Co-Cr coatings.
