Effect of TaC and TiC on the friction and dry sliding wear of WC–6 wt.% Co cemented carbides against steel counterfaces

The friction and sliding wear characteristics of a WC–6 wt.% Co alloy to which minor amounts of refractory carbides TiC, TaC and NbC were added have been systematically investigated. The wear behavior was characterized by sliding the carbide alloys against mild and 304 stainless steels in a pin-on-disc configuration and determining the associated wear mechanisms. The influence of applied load on the friction and wear response was also analyzed. The addition of less than 1 wt.% TaC was found to improve the wear resistance. The combined addition of TaC and TiC did not provide a significant improvement in the wear resistance. The friction response of the mild steel against each carbide grade followed the same pattern as sliding progressed, while that of the stainless steels was erratic. In general the 304 stainless steels had higher wear rates than the mild steels against all three carbide grades despite having a higher hardness. Oxidation of the steel and carbides reduced the friction at an increased applied load. No general correlation was found between the friction coefficient, the wear coefficient and the volumetric material loss for the carbide-steel sliding pairs. The dominant wear mechanisms for the carbides were typically preferential removal of the binder, cracking and fragmentation of the carbide grains, carbide grain pull-out and tribofilm formation. The dominant wear mechanism for the steels was plastic deformation with the TaC-hardmetal grade causing severe mechanical damage on the stainless steel surface.

► Addition of less than 1 wt.% TaC improved the wear properties of the 6 wt.% Co grade.
► Combined addition of TaC and TiC did not improve the wear resistance significantly.
► No direct correlation between applied load, friction and wear rate for all carbides
► Higher friction and wear rates against stainless steel than against mild steel