Abrasive micro-blasting to improve surface integrity of electrical discharge machined WC-Co composite

This study investigates the improvement of surface integrity of wire electrical discharge machined (EDM) WC-Co composite by abrasive micro-blasting. The thermally damaged recast layer generated by EDM has craters, cracks, and bubbles, which deteriorate the surface mechanical properties. The micro-blasting, using 6-12 and 4-20 μm size SiC abrasive, enables the removal of the recast layer and is suitable for micro mechanical components. The surface roughness of EDM rough cut WC-Co parts was improved significantly, with the average surface roughness (R_a) dropping down from 1.3 to 0.7 μm. Scanning electron microscope (SEM) was used to examine the evolution change of surface texture and subsurface cross-section of EDM WC-Co workpiece. The SEM micrographs showed that the recast layer was removed efficiently. After 5 s of micro-blasting, surface textures with ridge and cavity patterns were observed on fine and rough cut EDM surfaces, respectively. These surface textures could be correlated to the surface roughness measurement and crater formation in EDM spark erosion. A series of erosion wear experiment was conducted to quantify the weight reduction, calculate the erosion wear rate, and identify the wear mechanism.