와이어 방전가공이 초경과 두랄루민 표면의 화학 조성에미치는 영향

Abstract

The chemical composition of the wire electric discharge machining (WEDM) recasting layer must be analyzed, asit affects the surface properties of the product. This study examines the WEDM surfaces of cemented carbide(WC) and aluminum 7075 by (scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy(EDS). Up to 87% of the diameter of the WC cylinder is machined by a brass wire. However, cracks and fluidforces break the remaining 13%. The broken cross-section consists of 1- -㎛ sized WC grains bonded with cobaltmetal and without brass elements. Copper elements, which do not exist in WC materials, are then detected onthe convex spherical portion of the WC WEDM surface, and tungsten, which is the main component of thematerial, is observed on the lower surface. This indicates that some brass electrode particles that were removedby the spark adheres to the cemented carbide surface. The aluminum component is uniform, but theconcentration of the copper component is scattered irregularly. Therefore, some melted electrodes appear to beirregularly attached to the aluminum 7075 WEDM surface. The oxygen component is distributed more in theconvex than in the concave portion, which means that the convex portion of the aluminum is mainly oxidized toalumina. On the WEDM surface of the WC under a high melting point, 16.7 wt.% of zinc and 41.8 wt.% ofcopper, which were not detected prior to electric discharge machining, are detected. However, on the WEDMsurface of aluminum 7075 with a low melting point, increases of only 8.8 wt.% of zinc and 6.3 wt.% of copperwere observed.