An investigation into superficial embedment in mirror-like machining using abrasive jet polishing

This study performs experimental investigation into the application of abrasive jet polishing (AJP) to the surface finishing of electrical-discharge-machined SKD61 mold steel workpieces. The results indicate that the AJP processing conditions which optimize the surface quality of the SKD61 workpiece when polishing using #2000SiC abrasives are as follows: an abrasive material to additive ratio of 1:2, an impact angle of 30°, a gas pressure of 4 kg/cm2 (0.4 MPa), a nozzle-to-workpiece height of 10 mm, a platform rotational velocity of 200 rpm, and a platform travel speed of 150 mm/s. Under these processing conditions, a polishing time of 20 min is sufficient to reduce the surface roughness from an initial value of Ra = 1.7 μm to a final value of Ra = 0.27 μm, corresponding to an improvement of 84.12%. The experimental results demonstrate that the maximum attainable improvement in the surface quality of the polished workpiece is limited by a surface-hardening effect caused by the ball-impact phenomenon and the embedment of #2000SiC fragments in the workpiece surface.