Modeling of Martensite Transformation in White Layer under Thermo-mechanical Coupling in Hard-Cutting Process

Abstract

Martensite volume fraction determines the hardness and wear resistance of workpiece, predicting the martensite volume fraction of the white layer is of great significance for improving the surface quality of the workpiece. Accordingly, a theoretical model on the martensite volume fraction was developed in combination with the martensite transformation temperature model and the hard-cutting FE model. A finite element (FE) model of the hard-cutting was established to obtain the stress distribution of the workpieces. A calculation model of martensite phase transformation temperature $$M_{\text{S}}$$ under the influence of the cooling rate and stress was deduced based on the change of Gibbs free energy. A theoretical model of martensite volume fraction $$f_{\text{M}}$$ of the white layer was developed based on the $$M_{\text{S}}$$ and the FE simulations. The $$f_{\text{M}}$$ calculated by the theoretical model is in accordance with the experimental result. The effects of cutting speed, feed rate, flank wear and tool rake angle on the $$f_{\text{M}}$$ in the white layers were predicted and analyzed; the results show that the $$f_{\text{M}}$$ decreases first and then increases with the cutting speed, decreases with the feed rate and the flank wear, and increases with the tool rake angle.