Investigation of triaxial stress state in retained austenite during quenching of a low alloy steel by in situ X-ray diffraction

In situ XRD measurements were performed at ESRF, Grenoble, France (ID11) during quenching of a ball bearing steel AISI 52100 (100Cr6) with varying carbon content in solution. The evolution of austenite lattice parameter during cooling is nearly linear until Ms is reached and then, a divergent behavior can be observed. Assuming that the extrapolation of the linear range to room temperature gives the stress-free lattice spacing, an increasing compressive hydrostatic stress state is resulting. A strong effect of the carbon content was found. These results were confirmed by theoretical calculations based on data from the literature.