Precipitation Behavior of σ Phase in Ultra-Supercritical Boiler Applied HR3C Heat-Resistant Steel  

作　　者：Tie-Shan Cao Cong-Qian Cheng Jie Zhao Hui Wang 

机构地区：[1]School of Materials Science and Engineering,Dalian University of Technology,Dalian 116024,China [2]State Key Laboratory of Structural Analysis for Industrial Equipment,Dalian University of Technology,Dalian 116024,China

出　　处：《Acta Metallurgica Sinica(English Letters)》2019年第11期1355-1361,共7页金属学报（英文版）

基　　金：financials support by National Natural Science Foundation of China (No. U1610256);the National High Technology Research and Development Program of China (The 863 Program) (No. 2015AA034402);the Dalian University of Technology Fundamental Research Fund (No. DUT17RC(3)010)

摘　　要：The precipitation kinetics of σ phase in commercial HR3C heat-resistant steel during aging at 650–800 °C was studied in the paper. Through morphology, composition and structural analyzing on the second phase in the HR3C steel, it was confi rmed that the precipitations after aging were mainly NbCrN, M23C6 and FeCr type σ phase. The time-dependent mass change of the three precipitated phases showed that the linearly increased σ phase after aging at 750 °C–2000 h was transformed from NbCrN phase or M23C6 phase. According to the calculation on the volume fraction of electrolytically dyed σ phase, the time–temperature transformation(TTT) curve for σ phase at 1 vol% in two kinds of commercial HR3C steel(different in grain size) was obtained and analyzed. The nose of the TTT curve was located at around 750 °C for the two kinds of HR3C steel, and the larger grain size HR3C steel displayed a inhibit effect on the precipitation of σ phase. The impact energy of the HR3C steel after aging at 700 °C decreased obviously with the fracture mechanism changing from ductile fracture to intergranular brittle fracture, which was considered to be related to the density of σ-brittle phase after aging.The precipitation kinetics of σ phase in commercial HR3C heat-resistant steel during aging at 650–800 °C was studied in the paper. Through morphology, composition and structural analyzing on the second phase in the HR3C steel, it was confi rmed that the precipitations after aging were mainly NbCrN, M23C6 and FeCr type σ phase. The time-dependent mass change of the three precipitated phases showed that the linearly increased σ phase after aging at 750 °C–2000 h was transformed from NbCrN phase or M23C6 phase. According to the calculation on the volume fraction of electrolytically dyed σ phase, the time–temperature transformation（TTT） curve for σ phase at 1 vol% in two kinds of commercial HR3C steel（different in grain size） was obtained and analyzed. The nose of the TTT curve was located at around 750 °C for the two kinds of HR3C steel, and the larger grain size HR3C steel displayed a inhibit effect on the precipitation of σ phase. The impact energy of the HR3C steel after aging at 700 °C decreased obviously with the fracture mechanism changing from ductile fracture to intergranular brittle fracture, which was considered to be related to the density of σ-brittle phase after aging.

关 键 词：HEAT-RESISTANT steel AGING precipitation σ Phase TTT CURVE 

分 类 号：TG1[金属学及工艺—金属学]