Effect of thermal aging on GX4CrNi13–4 steels produced by direct energy deposition for pressurized water reactor

GX4CrNi13–4 steels have been a crucial material for manufacturing turbine impellers in pressurized water reactors. In this study, thermal aging resistance of GX4CrNi13–4 steels manufactured by direct energy deposition and traditionally forging was investigated and compared, including microstructural evolution and performance degradation. The results revealed that thermally aged traditional forging samples were subjected to a degradation in toughness due to precipitation of M₂₃C₆ carbides. In terms of direct energy deposition, the precipitation of carbides was restricted during aging by the help of the ferrite phase hence the degradation rate was much slower than that of forging samples, meaning that direct energy deposition process renders GX4CrNi13–4 steels higher thermal aging resistance. This study has revealed the advantage of minimal topological obstacles for direct energy deposition, which was considered to be an ideal method for preparing GX4CrNi13–4 steels.