Precipitation behavior and martensite lath coarsening during tempering of T/P92 ferritic heat-resistant steel

• Published in: International journal of minerals, metallurgy and materials Vol. 21; no. 5; pp. 438 - 447
• Main Authors: Xu, Lin-qing, Zhang, Dan-tian, Liu, Yong-chang, Ning, Bao-qun, Qiao, Zhi-xia, Yan, Ze-sheng, Li, Hui-jun
• Format: Journal Article
• Language: English
• Published: Beijing University of Science and Technology Beijing 01-05-2014; Springer Nature B.V; State Key Lab of Hydaulic Engineering Simulation and Safety, School of Material Science and Engineering, Tianjin University, Tianjin 300072, China
• Subjects: Carbon nitride; Cementite; Ceramics; Characterization and Evaluation of Materials; Chemical composition; Chemical precipitation; Chemistry and Materials Science; Composites; Corrosion and Coatings; Diamond pyramid hardness; Dislocations; Evolution; Ferritic stainless steels; Glass; Hardness; Heat resistant steels; Heat treating; High resolution electron microscopy; High strength steels; Light microscopy; Materials Science; Mechanical properties; Metallic Materials; Microstructure; Natural Materials; Optical microscopy; Precipitates; Stability analysis; Surfaces and Interfaces; Tempered martensite; Tempering; Thermal stability; Thin Films; Transmission electron microscopy; Tribology; X-ray diffraction; X-ray spectroscopy; X-射线衍射分析; X射线光谱仪; Y junctions; 回火马氏体; 析出行为; 粗化过程; 透射电子显微镜; 铁素体耐热钢; 马氏体板条; ferritic steel; coarsening; precipitation; tempering; heat resisting; martensite
• ISSN: 1674-4799; 1869-103X
• DOI: 10.1007/s12613-014-0927-4

Tempering is an important process for T/P92 ferritic heat-resistant steel from the viewpoint of microstructure control, as it facili- tates the formation of final tempered martensite under serving conditions. In this study, we have gained deeper insights on the mechanism underlying the microstructural evolution during tempering treatment, including the precipitation of carbides and the coarsening of martensite laths, as systematically analyzed by optical microscopy, transmission electron microscopy, and high-resolution transmission electron mi- croscopy. The chemical composition of the precipitates was analyzed using energy dispersive X-ray spectroscopy. Results indicate the for- mation of M3C （cementite） precipitates under normalized conditions. However, they tend to dissolve within a short time of tempering, owing to their low thermal stability. This phenomenon was substantiated by X-ray diffraction analysis. Besides, we could observe the precipitation of fine carbonitrides （MX） along the dislocations. The mechanism of carbon diffusion controlled growth of M23C6 can be expressed by the Zener＇s equation. The movement of Y-junctions was determined to be the fundamental mechanism underlying the martensite lath coarsening process. Vickers hardness was estimated to determine their mechanical properties. Based on the comprehensive analysis of both the micro- structural evolution and hardness variation, the process of tempering can be separated into three steps.