Sliding-wear performance of ZrC-Co: A comparative assessment under dry and neutral/non-neutral wet media

The sliding-wear behaviour of a newly-developed fine-grained ZrC-16.693 vol%Co cemented carbide was investigated, and critically compared under frictional contact in four media (i.e., dry wear, and wet wear in neutral water (pH-7.1) and in highly acidic (pH-1.1) and alkaline (pH-13.7) aqueous solutions). It is shown that, under the testing conditions used (i.e., 20 N for 1000 m at 5 cm/s), because this ZrC-Co cemented carbide is superhard (-18 GPa), it only undergoes mild wear in the four media, with specific wear rates of the order of 10-6 mm3/(N.m) or less. It was also identified that wear occurs by abrasion (wear mode) controlled by plastic deformation plus some localized fracture (wear mechanisms), with varying severities depending on the wear medium. Importantly, wear in water was comparatively the least, mainly attributable to water imposing moderate lubrication without any sign of chemical attack. Wear in alkaline medium was only slightly greater than in water, mostly imputable to the alkaline aqueous solution imposing moderate lubrication without attacking the ZrC grains and only slightly the Co binder. Dry wear was greater than wear in both water and alkaline medium, imputable to the greater severity of the frictional contact. And lastly, wear in acidic medium was comparatively the greatest, principally imputable to the acidic aqueous solution imposing moderate lubrication without attacking the ZrC grains but dominantly leaching the Co binder. In sum, ZrC-Co was found to be at least little susceptible to the non-neutral wet wear, and therefore in principle could form the basis of a subfamily of cemented carbides highly recommendable for use in tribological applications involving harsh environments.