Analytical multi-physics model of microstructure changes in hard turning of AISI 52100 steel: prediction of thicknesses of white and dark layers

Hard turning is more and more considered by the industry as a possible and good option for the process of grinding or pre-grinding. However, it is hurdled to a very great extent by surface integrity problems, to wit, for example, the microstructure transformations and the tensile residual stresses (white layers (WLs) and dark layers (DLs)), which are generally found to have negative effects on the stress corrosion, wear resistance, and fatigue life of machined parts. The optimization of this process has become the focus of experts. This paper presents a thermo-mechanical model able to predict the thicknesses of WLs and DLs during the orthogonal cuts of the hardened steel AISI 52100. The model combines the temperature, stress, and strain effects on the phase transformation mechanism to predict the thicknesses of layers. Unlike a similar model, presented in the literature, our developed approach firstly predicts the cutting forces for each tested condition. Secondly, it evaluates the thermo-mechanical loads on the machined surface. Thirdly, it evaluates the austenite transformation temperature. Therefore, it is possible to predict the WL and DL thicknesses for selected cutting conditions. This multi-physics model provides cutting force and layer thickness results close to those obtained experimentally in the literature. Analyzing the effect of the cutting conditions on the affected layer thickness reveals that the WL thickness increases with the rise in the cutting speed and the feed rate. Moreover, the flank wear has a greater effect on the thicknesses of layers.