Surface modification of AISI H13 tool steel with silicon or manganese powders mixed to the dielectric in electrical discharge machining process.

In electrical discharge machining (EDM) process, one of the most important aspects is the surface quality of the workpiece. When a uniform and thick recast layer is achieved with characteristics of low roughness, high hardness, and the absence of pores and micro-cracks, it acts as a kind of coating. Such surface is required by mold-making industry, where the molds are subjected to chemical and abrasive wear, and the surface needs to present high resistance against corrosion and abrasive forces. The use of powder particles suspended in the dielectric is a way to provide such improvement and, at the same time, avoiding the need for subsequent polishing. This work investigated the influence of silicon and manganese powders with fine particle sizes, using two different concentrations, suspended in the dielectric when EDM machining AISI H13 tool steel. It evaluated the surface roughness, hardness, and the chemical composition and micro-structure of the recast layer; using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) techniques. The best results were obtained for silicon powder; presenting the surface roughness improved about five times, when compared to the conventional EDM process, as well as a thick and uniform recast layer without micro-cracks and pores. The silicon and the manganese powders also promoted an increase of the recast layer hardness of about 40 % when compared to the conventional EDM process. [ABSTRACT FROM AUTHOR]