Wear modes in slurry jet erosion of tungsten carbide hardmetals: Their relationship with microstructure and mechanical properties

Hardmetals based on tungsten carbide (either with a cobalt binder or cobalt/nickel binder) have been subjected to slurry jet erosion, using silica sand or alumina erodent entrained in a water jet. Wear processes have been identified in a number of hardmetals and results correlated with conventional parameters used for assessing hardmetals (hardness, binder linear intercept, WC grain size). Results were obtained using two principal impingement angles; normal incidence (90°) and 45°, and were correlated with bulk hardness but the relationships that were found differed in detail from those for abrasion. Local microstructure, evidenced by electron microscopy on wear scars and cross-sections, appears to play a more fundamental role in the respect of material response to erodent impact, with WC grain size being a major determinant. The type of erodent used had a significant effect on material response; microscopic plastic grooving occurred readily with an alumina slurry jet, but was not evident in the case of silica sand. 3-D spatial analysis via a confocal optical microscope and also a non-contact scanning eddy current probe of wear scars have also used to characterise their shape and extent of degradation respectively.