Abrasive Water Flow Polishing of Superalloy Microholes Drilled by Electrical Discharge Machining

Superalloy microholes resulting from electrical discharge drilling (EDD) can have recast layers and microcracks on the machined surfaces. In this study, the abrasive water flow polishing (AWFP) of superalloy microholes machined by EDD was investigated. The recast layer and surface roughness resulting from the EDD process were evaluated through orthogonal experiments. The machining mechanism of AWFP was analyzed. The effects of AWFP parameters were investigated experimentally. The results show that the material removal rate and surface roughness at the hole exit were better than those at the entrance for one-directional fluid flow during the process. Garnet abrasives achieved better polished roughness and a lower material removal rate than alumina abrasives. The taper angle of the target holes changed slightly from positive to negative after AWFP. The corner edge was slightly rounded on the fluid inlet side. Using a bidirectional fluid resulted in better dimensional uniformity and surface roughness at the entrance and exit. This study verified that AWFP can remove the recast layer and microcracks on the hole wall caused by EDD and reduce the surface roughness from an initial Ra of 5.7 & mu;m to an Ra of 0.6 & mu;m.