Investigations on Surface Integrity of Heat Treated 42CrMo4 (AISI 4140) Processed by Sinking EDM

Adjusting a resulting surface integrity prior to a manufacturing process is a big challenge in production engineering. One approach to solve this challenge is the methodology of process signatures. To develop a comprehensive process signature for Sinking EDM (S-EDM) it is necessary to describe the relationship between the applied material loadings and resulting modifications in the workpiece rim zone. It is generally considered that S-EDM is an electro-thermal process, which is significantly characterized by the heat flux due to the spark plasma. Accordingly, the main loadings during S-EDM are the arising temperatures and their temporal as well as spatial gradients in the workpiece. These loadings lead to varied surface integrity modifications. Thus, the task is to investigate the surface integrity alteration according to the initial material condition. Consequently, in this paper the effect of different annealing and heat treatment states of 42CrMo4 (AISI 4140) on the S-EDM process were investigated. Hence, changes of state variables depending on different machining parameters and the varying dissipated energy were considered. Therefore, the resulting microstructures were analyzed by scanning electron microscope (SEM). Additionally residual stress was determined and compared to the initial state. The identified changes of investigated state variables are the described modifications. (C) 2016 The Authors. Published by Elsevier B.V.