Combined machining of SiC/Al composites based on blasting erosion arc machining and CNC milling

Abstract

In this study, a combined method is proposed for the machining of SiC/Al matrix composites to achieve high efficiency and better surface quality based on blasting erosion arc machining (BEAM) and computer numerical control (CNC) milling. The combined method consists of two stages. BEAM is adopted in the first stage to achieve a high machining efficiency. During this stage, the negative BEAM is used for improving material removal rate (MRR) while positive BEAM is adopted to reduce roughness of machined surface. In the second stage, CNC milling is utilized to achieve a fine surface. Firstly, in order to perform the combined processing, a special machine tool system is designed. Secondly, machining efficiency of the combined processing is discussed. It is disclosed that in the negative BEAM step, when peak current is 600 A, MRR of 20 vol.% SiC/Al and 50 vol.% SiC/Al composites can be as high as 10,200 and 7500 mm3/min separately. Thirdly, comparison experiments are designed and surface integrity (e.g., surface topography, surface roughness, heat affect zone, surface hardness, compositions) of each machining stage is analyzed. It is demonstrated that in the CNC milling stage, side effects of BEAM on the workpiece (e.g., rough surface, thick heat affect zone) can be eliminated effectively. The roughness of the machined surface can be lower than Ra 0.5 μm; heat affect zone (HAZ) and debris almost cannot be observed. Finally, a SiC/Al workpiece is machined to demonstrate the advantages of the combined machining of SiC/Al matrix composites.