It is well known that shot-peening on cemented carbide tools such as cutting tools coated with hard materials and sliding parts has often been applied. However, the change of surface structure by shot-peening seems scarcely to be so far made clear. Then, the study on this subject for un-coated WC-15mass%Co and -15mass%Ni alloys was undertaken using mullite beads of 80-200 mesh.
It was found that the rate of fracture of surface layer by shot-peening was larger in coarse grained Co and Ni alloys than fine grained alloys, and it was larger in both alloys by use of coarser beads. It was also found that, to get a flat and uniformly fractured surface, the role of microstructures of the alloy and bead size were particularly of importance.