M. R. Ahmadi, F. Meixner, M. Dománková, M. Raus, B. Sonderegger, C. Sommitsch
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引用次数: 0
摘要
与传统的马氏体钢(如 MarBN)相比,15%-Cr 铁素体钢由于铬含量高、蠕变强度高、位错密度低和缺乏板条微结构而具有更好的抗氧化性。它们的机械性能对化学成分和热处理很敏感。在本研究中,我们首先使用热力学软件 MATCALC 模拟了两种含 2% 镍(重量百分比)的铁素体钢和一种不含镍的合金中稳定相的形成。利用扫描电子显微镜(SEM)和能量色散 X 射线光谱(EDS)进行的微观结构分析表明,无论是在油中快速冷却还是在炉中缓慢冷却,扩散退火后都会形成碳化物和金属间相。稀释测量法和 XRD 研究证实,在加热过程中,从 650 °C 开始,铁素体逐渐转变为奥氏体。稀释测量法还表明,铁素体钢的热膨胀系数低于马氏体钢、奥氏体钢和超合金,因此在发电厂频繁启动和关闭期间,热应力较低。
Microstructural characterization of 15Cr steel after quenching and slow cooling rates
Ferritic 15 %-Cr steels have better oxidation resistance, due to their higher chromium content, and creep strength, their lower dislocation density and lack of lath microstructure than conventional martensitic steels such as MarBN. Their mechanical properties are sensitive to chemical composition and heat treatment. In this study, we first simulated the formation of stable phases in two ferritic steels containing 2 % nickel (wt.%) and an alloy without nickel using the thermomechanical software MATCALC. Microstructural analysis using scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) reveals the formation of carbides and intermetallic phases after diffusion annealing, both during rapid cooling in oil and slow cooling in the furnace. Dilatometry and XRD studies confirm the gradual phase transformation of ferrite to austenite from 650 °C onwards during heating. Dilatometry also shows that ferritic steels have a lower coefficient of thermal expansion than martensitic steels, austenitic steels, and superalloys, which results in lower thermal stresses during frequent start-up and shutdown of power plants.