An investigation on surface integrity and microstructure behaviour of AISI 304 stainless steel machined by die sinking EDM

Abstract

Machining of AISI 304 enables the customization of parts to meet specific mechanical and aesthetic requirements, ensuring optimal performance and durability in various applications. In this study, electrical discharge machining (EDM) is introduced to machine AISI 304 stainless steel. To accomplish the desired machining characteristics (MRR, SR), different EDM factors are chosen, such as discharge current, pulse on time, and pulse off time. The experiment is planned using central composite design in response surface methodology (RSM). The impact of EDM variables on metal removal rate (MRR) and surface roughness (SR) is examined through surface plot. Regression coefficient values for MRR and SR are 92.37% and 83.28%, respectively, indicating an empirical relation between the factors and responses. The lack of fit values for MRR and SR were 3.87 and 1.49, respectively, which were lower than the average values. Thus, the developed model was sufficient. It was observed that MRR and SR increases with increase in all parameters, but decreases at higher range of parameters. As current and pulse on time increase, the ionization temperature generated in the machining zone which removed more quantity of materials from the workpiece. Due to ionization temperature, more craters and voids formed which made surface irregular and hard, resulted increased SR. At lower level of discharge current and pulse on time, insufficient spark intensity is developed which made cracks and globules on the surface. The estimated error of actual and expected values for MRR and SR are 7.07% and 5.12% respectively. The desirability of optimization was calculated to be 0.9710, indicating that parameters are within acceptable conditions.