Improving the Surface Properties of OHNS Die Steel Using Electrical Discharge Machining Process

Electrical Discharge Machining (EDM) is widely used for manufacturing plastics moulds, die casting dies and forging dies from hardened tool steels. The intrinsic nature of the process results in erosion of the tool material and some of it is found In the machined surface under specific machining conditions. Deliberate material transfer may be carried out by using either composite electrodes or by dispersing metallic powders in the dielectric. This paper describes the formation of plasma channel during EDM sparking and how it may be utilized for improving the surface properties of die steels by selective material deposition on the machined surface from the eroding electrode. The OHNS die steel work material has been machined using copper, copper-chromium and copper-tungsten electrodes under process parameters favouring high tool wear. The SEM and EDS analysis of the machined surfaces show alloying of parent material with copper, chromium and tungsten which result in the Improvement of surface properties such as wear resistance and strength at elevated temperatures.