Micro-abrasion investigations of conventional and experimental supercoarse WC-(Ni, Co, Mo) composites

Abstract Typically the wear resistance of hardmetals is assessed employing ASTM G65 and ASTM B611 tests. Both these methods employs abrasives of grain size larger than 200 μm. In numerous applications (e.g. effluent pumps) sintered carbides are exposed to wear by fine hard particles and micro-abrasion test is an appropriate method for materials selection and assessment. The relevant standard (BS EN 1071–6) recommends 4.5 μm SiC abrasives. It was found that in the case of supercoarse sintered carbides (6–10 μm WC grain size) this micro-scale test produces ill-defined craters difficult to measure accurately. Therefore, through an optimization procedure, the threshold grain size of hardmetals to be tested with 4.5 μm SiC as well as the abrasive medium for micro-abrasion testing of coarse and supercoarse grades were established. Diamond slurry (1 μm average grain size) produces well-defined craters through the grooving mechanism. Using these optimised abrasives, conventional WC-Co and WC-(Ni-Mo, Ni-Co-Mo) supercoarse hardmetals were tested. The supercoarse grades, regardless of the type of metal matrix, proved to be more wear resistant than finer grained sinters. Larger WC grains, within the supercoarse group, are also conducive to lower abrasion rate.