Influence of magnesium treatment on inclusions and primary carbides in As-cast H13 die steel

Abstract

In this study, the inclusions and primary carbides in H13 hot-work tool steel were investigated, both with and without magnesium treatment, utilizing various analytical techniques such as optical microscope (OM), scanning electron microscope (SEM), energy-dispersive spectroscopy (EDS), and quantitative analysis methods. Furthermore, the experimental results were compared with the calculations obtained from Thermo-Calc software. The results revealed that as we move from the edge to the center of the steel, the equivalent diame-ter of inclusions increased. However, upon adding magnesium to the steel, the size of inclusions decreased, while the number of inclusions per unit area increased. The primary carbides found in H13 steel consisted of vanadium-rich MC carbides and molybdenum-chromium-rich M2C carbides. The addition of magnesium had a significant impact on the size of these primary carbides. The presence of MgAl2O4 particles acted as heterogeneous nuclei, providing nucleation sites that induced smaller sizes and more uniform distribution of primary carbides. Furthermore, it was observed that the banded segregation in the annealed microstructure became more uniform after magnesium treatment, leading to an improvement in the banded segregation.