The Microhardness on Wire-EDM'd Surface

Abstract

Thermal erosion process in wire-EDM influences metallurgical integrity on its machined surface, especially the change of microhardness may cause abnormal wear and/or microchipping of the EDM'd tools. This paper describes the behaviour of the microhardness in machining steels. The results obtained are summarized as follows : (1) Machining under de-ionized water makes surfaces hardened to an annealed steel, but re-softened to a quenched & tempered steel by a formation of the austenite. (2) Machining under the oil, both an annealed and a quenched & tempered steels are re-hardened by a increased carbon content from the dielectric fluid. (3) The discharge energy influences the hardness variations, the microhardness neighbouring to the machined surface are effected by each dielectric fluid, but not by the heat treatment conditions of the workpieces.