In-situ Investigation of Bainite Formation with fast X-Ray Diffraction (iXRD)*

Abstract

Abstract Using specific equipment for high temperature fast in-situ X-ray diffraction (iXRD) enables the collection of diffraction patterns over a range of 48 degrees in 2θ within one second. In combination with a high-temperature furnace, modifications in the crystallographic structure under a thermal treatment like phase transformations in steel can be observed nearly in real-time. We demonstrate the usefulness of fast high temperature iXRD using the ball bearing steel (100Cr6), which is of high industrial importance for many applications. The specimens were austenitized at 860 °C. Various isothermal annealings were carried out to develop a bainitic steel structure. The transformation was interrupted by further cooling at different stages. The specimens were further investigated with SEM and light microscopy using different etching techniques to correlate the microstructure with the diffraction patterns. We will show that iXRD can help to optimize heat treatments, validate time transformation diagrams and increase the understanding of phase transformations in steels.