Research on microstructure evolution and carbide transformation behavior during the quenching and tempering processes of secondary hardening steel

作者：Yaxu Zheng, Shaokang Chu, Long Zhang, Qi Wang, Guibao Qiu, Liguang Zhu, Zhihong Guo, Tianwei Xie, Hairui Zhao, Suling Lu, Bo Wang, Jie Feng · 发表于：Journal of Materials Research and Technology · 年份：2025 · DOI：10.1016/j.jmrt.2025.05.059 · 被引用次数：8 · 研究领域：Microstructure and Mechanical Properties of Steels、Metal Alloys Wear and Properties、Metallurgy and Material Forming

The microstructure evolution, solution and precipitation of precipitated phases and mechanical properties of Co-free and low-Ni secondary hardening steel, upon quenching and tempering were studied using optical microscopy (OM), transmission electron microscopy (TEM), electron backscatter diffraction (EBSD), and microhardness testing. Based on these results, the effects of quenching media and tempering temperatures on the microstructure and properties of alloy steel are discussed. The results showed that when the quenching temperature was 1050 °C and air or oil cooling was adopted, some lower bainite was generated in the microstructure, and <100 nm V-rich MC-type carbides ( M= V, Mo, or Ti) precipitated during the air cooling process. The microstructure is martensite after austempering at temperatures between 350 °C and 500 °C. MC carbides precipitate during the austempering process, and the quantity of precipitated carbides increases with higher temperatures and prolonged time. When tempered at temperatures between 200 °C and 400 °C, internal stress is reduced, and dislocations are recovered, resulting in a decrease in hardness. When tempered at 550 °C, a significant amount of carbides precipitate, primarily including M 3 C and M 2 C. The fine M 2 C carbides exhibit a secondary hardening effect, resulting in maximum hardness. When the tempering temperature is higher than 550 °C, the size of M 2 C carbides increased and coarsened into short rod-like shapes. M 23 C 6 precipitat...