Effects of the Inductive Hardening Process on the Martensitic Structure of a 50CrMo4 Steel*

Abstract

Abstract This study focuses on the influence of a fast heat treatment, as occurring with induction heating processes, on the microstructural features, and their effect on the mechanical properties of a 50CrMo4 steel. To this end, three different heating rates (1 K/s, 10 K/s, and 100 K/s) and three different austenitizing temperatures (950 °C, 1000 °C, 1050 °C) were applied to a ferritic-pearlitic steel. After quenching, the resulting martensitic microstructures were investigated and compared to a conventional furnace heat treating sequence using electron back scattered diffraction (EBSD). Thus, the effect of variable heating rates during austenitization on the resulting martensitic microstructure, including the evaluation of packet and block sizes and orientations, was analyzed. Through the investigations of this work, it could be shown, that the adaption of the Kurdjumov-Sachs (K-S) variants is changing with the prior heat treatment. The occurrence of all 24 K-S variants in the same intensity increases and the misorientation angle across a martensite block decrease with higher austenitizing temperatures, despite fast heating rates. Therefore, it is suggested, that the austenitizing temperature has more impact on the martensitic structure than the heating rate.