Microstructure evolution and mechanical properties in 1Cr low alloy steel with different heat treatments

Abstract This work investigates microstructures, precipitates, and mechanical properties in 1Cr low alloy steel undergoing normalizing, quenching, and quenching-tempering treatments. The precipitated phases in these samples were removed by electrolytic extraction and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The precipitates extracted from the normalized and tempered samples were mainly M 3 C cementite, while the major precipitates obtained from the quenched sample were identified as Nb-rich MC carbides. Energy dispersive X-ray spectroscopy (EDXS) semi-quantitatively analyzed the ratios of Fe atoms to Cr atoms in relevant phases, revealing that redistribution of Cr occurred in the tempering process but not in the normalizing or quenching processes. The tempered sample contained M 3 C carbide with a {022} twin plane and a hexagonal M 7 C 3 -type phase. Strength and elongation in the quenched sample were larger than these in normalized sample, but a significant reduction in strength and a dramatic increase in elongation occurred when the as-quenched sample was tempered.