The solid particle erosion of WC-Co alloys
An investigation involving the erosion of WC-Co alloys by solid particle impact erosion was undertaken to determine the mechanism by which material is removed. For this purpose a simple particle-gas stream erosion apparatus was employed. The nineteen different WC-Co alloys studied were initially characterised according to mi crostructural and mechanical properties. An investigation of the influence of various parameters on erosion was conducted to establish the manner by which the WC-Co alloys were eroded. A limit in erosion rate occurred with increasing particle size for all samples, which is associated with ductile erosion. The variation of erosion rate with the angle of impact was found to be dependent on the binder content. A maximum in erosion occurred at a 90u angle of incidence for the low cobalt content alloys and in the region of a SOU angle of incidence for high cobalt content alloys. Thus suggesting a predominantly brittle mode of erosion, with a ductile mode becoming more important with increasing binder content. The erosion rate was found to increase with decreasing hardness. For impact angles of 45u and greater, the hardness effect was masked by microstructural influences. Examination of the steady state eroded surface and the single particle impact event, using the scanning electron microscope revealed three modes of material removal. These may occur simultaneously, the predominant mode, however, changes with binder content. For WC-Co alloys containing less than 10 wt-% cobalt, cobalt extrusion was observed as being the controlling mode of material removal. Maximum carbide grain cracking was associated with a cobalt content of 10 wt-%. Above this binder level ductile cutting of the matrix became an increasingly important mode of material removal.
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