Spray electrolyte plasma polishing of GH3536 superalloy manufactured by selective laser melting

Abstract

Electrolyte plasma polishing (EPP) is an innovative and efficient technology mainly used to polish complex metal products and obtain surfaces with low roughness and high gloss. However, limited by the electrolyte bath size, EPP method is not suitable for polishing workpieces with large size. This paper introduces a spray electrolyte plasma polishing (SEPP) method that can process large-scale and complex surface. The theoretical mechanism of SEPP is presented. GH3536 superalloy plates manufactured by SLM were used as the experimental specimens. The influence of cathode feed velocity on surface roughness is studied. Key parameters, like distance between anode and cathode, voltage, temperature, and flow rate of the electrolyte were investigated experimentally. Properties such as surface roughness, micro morphology, chemical composition, and surface hardness of the GH3536 specimens were detected and analyzed. The results show that SEPP technology can decrease the specimen surface roughness from Ra = 13.93 μm to 0.107 μm and obtain a smooth and glossy surface without obvious machining traces. The oxides and other impurities on the specimen surface were removed, and the contents of Ni, Cr, and Fe elements were increased. Additionally, the surface hardness values of the polished specimen were increased and showed good consistency.