5.5Al-AFA耐热钢高温蠕变行为研究

Study on high temperature creep behavior of 5. 5Al-AFA heat-resistant steel

面向超超临界发电机组用钢,设计、制备了5.5Al-AFA耐热钢材料,基于不同加载应力条件的蠕变实验与微观组织分析,研究了该耐热钢的蠕变特征与蠕变损伤机理。结果表明,该耐热钢具有典型金属材料的蠕变特征,加载应力对蠕变断裂时间影响显著,在温度为750℃、加载应力为120和250 MPa下的蠕变断裂寿命分别为1711和1.5 h,材料表观应力指数达5.18,蠕变机制为位错攀移,蠕变激活能为418.44 kJ·mol^(-1)。蠕变过程中析出的脆性σ-FeCr相导致应力集中与材料断裂,失效形式为微孔密集型韧性断裂。

5.5Al-AFA heat-resistant steel material was designed and prepared for ultra supercritical power generation units.The creep characteristics and creep damage mechanism of the heat-resistant steel were studied through creep experiments and microstructure analysis under different loading stress conditions.The results show that the heat-resistant steel has typical creep characteristics of metallic materials,and the loading stress has significant effect on the creep fracture time.When the temperature is 750℃and loading stress is 120 and 250 MPa,the creep rupture life is 1711 and 1.5 h,respectively.The creep mechanism is dislocation climb according to apparent stress index of the material with 5.18 and creep activation energy reaches 418.44 kJ∙mol^(-1).The brittleσ-FeCr phase precipitated during creep process leads to stress concentration and material fracture,and the failure mode is ductile fracture with dense micro-pores.