Abstract
Safety critical engine components, whose functionality and longevity demands a high surface integrity, are widely made of the direct aged nickel-based alloy DA718. The high strength and low thermal conductivity of DA718 lead to high thermal loads, which causes modifications of the microstructure in the rim zone. Changes in grain size can result in cracking and thus detrimentally affect component functionality. According to the current state of the art, numerical simulation methods can be used to model the machining induced rim zone modification. For this purpose, experimental investigations of orthogonal cutting and friction tests were performed to determine the viscoplastic properties of the DA718 and frictional behavior between workpiece and tool. Based on this, a turning simulation was developed using the Coupled Eulerian-Lagrangian (CEL) method. This is followed by the implementation of a numerical model for the prediction of grain size changes in the workpiece rim zone. To validate this model, face turning tests of DA718 was performed with a ceramic tool, and the grain size alterations were compared with the simulation. The Comparison showed, that the model agreed well with the experimental measurements for different cutting conditions.
