新型耐热钢HR3C在超超临界机组高温服役25000h后的性能研究

Performance on New Heat-resistant Steel HR3C in the Ultra-supercritical Units After Service at High Temperature for 25000 Hours

通过对材料性能、金相、扫描电镜(scanning electronmicroscope,SEM)、能谱(energy disperse spectrum,EDS)、氧化皮、碳化物萃取、透射电镜(transmission electronmicroscope,TEM)等的分析,对在超超临界机组运行5 400和25000h的新型奥氏体耐热钢HR3C进行老化研究,经研究表明HR3C运行25000h后性能的变化主要表现为向火侧室温抗拉强度上升4%,屈服强度下降10%;650℃拉伸性能略有下降;压扁时有脆化,硬度明显提高,表明已发生时效强化;内外壁氧化皮形成致密的Cr2O3层;组织无明显老化,析出物主要为Z相、M23C6和M6C型,碳化物沿晶界较明显析出;运行25000h后析出的碳化物中M6C和M23C6含量明显高于运行5 400 h后析出的含量,表明已有M23C6型碳化物向M6C型碳化物过渡。

Through the analysis of the performance, metallographic, scanning electron microscope （SEM）, energy disperse spectrum（EDS）, oxide, carbide extraction, and transmission electron microscope（TEM）methods, the aging research of the new austenitic heat-resistant steel HR3C was conducted in ultra-supercritical units after service for 5 400 hours and 25 000 hours. The research shows that after service for 25 000 hours the performance of HR3C changes： the main tensile strength increases by 4%, yield strength decreases by 10%; 650 ~C tensile properties decrease slightly; it becomes brittle when being crushed, the hardness is increased observably, indicating that aging has taken place to strengthen; a dense oxide layer of Cr203 is formed in outer and inner oxide scale; tissue had no significant aging, precipitat6s are mainly Z-phase, M23C6 and M6C , carbide was obviously precipitated along the grain boundaries; the content of M6C and M23C carbide precipitation after service for 25 000 hours is significantly higher than after service for 5 400 hours, which showed that a part of M23C6 carbide precipitation had been transformed into M6C carbide precipitation.