Surface modification of stainless steel using EDM with TaC powder additives

Abstract

Recently, there has been an increased interest in the novel application of electrical discharge machining process (EDM) for competitive alternative to the traditional surface modification techniques i.e. ion implantation, laser surface melting etc. Besides the erosion of work material during the process and removal of some tool materials, the formation of plasma channels consisting of materials vapors from the eroding working materials and tool material affects surface composition and hence its properties. This suggest that it may be possible to carry out significant materials transfer under specific machining conditions by using either composite electrode or by dispersing metallic powders in dielectric or combination of both. But the use of conventional electrode for the surface modification process has not generated much success. The use of powder additive via EDM technique to improve the level of surface modification has been considered but this has not been exhaustively investigated. Besides, the existing research works limit the study of influence of process parameters on surface modification to two input parameters of pulse current and pulse duration leaving out pulse interval. This has prevented comprehensive optimization of the process to describe the relationship between the controllable independent variables and the machining parameters. These missing links needs to be investigated in order to determine the suitability of surface alloying of metallic materials using EDM, the appropriate settings for its associated independent controllable factors and also to take advantage of the attraction offer by the EDM technique. In the present research, attempt has been made to evaluate the performance of Tantalum Carbide (TaC) powder additive on surface alloying of stainless steel using EDM in terms of surface roughness (SR), tool wear rate (TWR), micro-hardness (HV), material removal rate (MRR), percentage material migration and corrosion resistance. In addition to EDM machining studies, the research will also involve the development of mathematical models and the optimization process, which describe the relationship between the controllable independent variables and the machining parameters. It is seen that the information obtained from this study has provided good insight into determining the suitability of the surface alloying of stainless steel using EDM and its appropriate settings for the associated independent controllable factors. Stainless steel is used for a range of applications in the aerospace, marine, power generation, offshore, automobiles and biomedical industries. In this regards, better surface integrity of this alloy will enhance its applications in many areas. TaC is an extremely hard, having very high melting point near 4270K (40000C). For experiments here TaC has been used to enhance the physical properties of stainless steel by comparison with conventional EDMed. All the experiments have done in two conditions: with and without TaC. The surface roughness and hardness has been improved by 13% and 38.7% respectively. Tool wear rate is reduced up-to 37.9%, the material removal rate has been increased by 44.8%. Moreover, with TaC, a small increase in material migration has been noticed and also the presence of micro-crack reduced on the surface. Obtain results showed that improvement has been achieved in terms of all response parameters and these findings of this study will equally increase the possibility of incorporating the surface alloying of stainless steel with EDM machine.