HR3C耐热钢在高温蠕变过程中微观组织演变分析

Analysis on Microstructure Evolution of HR3C Heat Resistant Steel during High-temperature Creep Test

利用OM、XRD、EDS和TEM对高温蠕变试验后的HR3C耐热钢试样的微观组织、析出相和裂纹进行了研究。结果表明:HR3C奥氏体耐热钢原始奥氏体组织中分布有细小、弥散的CrNbN第二相;在700℃高温蠕变试验中,随着试验时间的延长,HR3C耐热钢中将不断从奥氏体晶界析出大量的(Fe,Cr)_(23)C_6相;当应力大于110 MPa时,应力大小是影响高温蠕变试验中试样断裂的主要因素,断裂方式属于穿晶断裂,而应力小于110 MPa时,引起HR3C断裂的主要因素是沿晶析出的(Fe,Cr)_(23)C_6析出相,断口属于沿晶断裂;当表面具有较多数量大尺寸晶粒与小尺寸晶粒配合时,有利于抑制裂纹的萌生和扩展,提高HR3C耐热钢的高温蠕变寿命。

The microstructure, precipitated phases and crack of HR3C heat resistant steel after high temperature creep test were studied by OM, XRD, EDS and TEM. The results show that the tiny and dispersed second phase CrNbN distributes in original austenitic microstructure of HR3C anstenitic heat resistant steel. During high temperature creep test at 700℃, with the extension of experiment time, a large number of （Fe,Cr）23C6 phases continuously precipitate along austenite grain boundaries. When the stress is higher than 110MPa, the stress is the main factor affecting the fracture of HR3C and the fracture mode is transgranular fracture. However, when the stress is less than 110 MPa, the main factor of the fracture of HR3C is brittle （Fe, Cr）℃6 precipitated phase and the fracture mode is intergranular fracture. When there are a certain number of large size grains and small size grains in the sample＇s surface, it is benefit to suppress the initiation and propagation of crack. Then, the high temperature creep life of HR3C heat resistant steel improves.