Powder Bed Fusion (PBF) is a manufacturing process for producing complex tool geometries with improved performance. However, the high thermal gradients and solidification velocities during PBF can impact the solidification mode, which in turn affects the microstructure and performance of the manufactured components. In this study, we used synchrotron-based, high-speed X-ray diffraction setups to investigate the impact of thermal gradients and solidification velocities on the solidification mode of a hot-work tool steel.
Our results show that primary δ-ferrite is observed at a lower cooling rate, while at a higher cooling rate, δ-ferrite is suppressed, and primary austenite is observed. We linked the thermal conditions during the experiments to a solidification model based on the dendrite growth model by Kurz-Giovanola-Trivedi (KGT), and our modelling results predict the experimental observations.
This work demonstrates how in-situ XRD measurements can be used to understand the microstructure evolution and validate computational thermodynamics and kinetics models, enabling the development of alloys and process parameters for additive manufacturing.