Erosion of hardmetals: Dependence of WC grain size and distribution, and binder composition

A liquid jet erosion rig was constructed to test hardmetals of interest to the petroleum business sector. Accurate control of eroding silica particles, jet velocities (74, 56 and 37 m/s) and impact angles (90, 60 and 45°) were the main purposes. Hardmetals with varying binder content (5–7 wt%), binder composition (Co and CoNiCr), tungsten carbide particle size (0.6–3.5 μm) and particle size distribution were tested. The obtained velocity exponent of 3.4 indicates a typical level for this kind of materials, and showed that the rig was performing according to the intentions. An 80% reduction in grain size reduced the erosion level to 30–50% in hardmetals with pure Co binder, at a jet angle of 90°. The greatest effect was obtained at 74 m/s jet velocity. Hardmetals with the mixed binder and the same carbide size (about 0.6 μm) showed a reduction in erosion rate of about 65% at all jet velocities. The erosion rate was reduced by 15–20% when jet angles were reduced from 90° to 60°, and similarly when reduced from 60° to 45°. The erosion classification level, ECV, indicated that lower carbide size and lower impingement velocity change the erosion from brittle to a more ductile mode.