ROF炉內罩用YUS701钢服役前后的对比分析

Comparative analysis of YUS701 steel before and after service in ROF furnace for long time

利用光学电镜、扫描电镜及能谱分析和透射电镜等方法对ROF炉內罩用YUS701钢服役前后的微观组织、析出行为及力学性能变化进行了分析。结果表明:试样经长期服役后,奥氏体晶粒发生了严重长大,细晶强化作用减弱,造成材料室温强度的降低,同时试样中发生了较严重的晶间腐蚀;服役前试样的晶内主要有条片状的M_2(C,N)亚稳相析出物,奥氏体中的位错密度高;而服役后试样的位错密度降低,且晶界处有大块状M_(23)C_6相析出,以及晶内析出了长条状的σ相,容易成为裂纹源并使裂纹沿晶界扩展,从而使材料的高温强度、塑性和韧性降低。

Microstructure, precipitation behavior and mechanical properties evolution of YUS701 steel before and after service in ROF furnace for long time were investigated by means of optical microscope （OM） , scanning electron microscopy （SEM） , energy dispersive spectroscopy （EDS） analysis and transmission electron microscopy （TEM）. The results show that after long time service, grain refinement strengthening is weakened and room temperature strength decreases due to the grain size of austenite increases significantly. Meanwhile intergranular corrosion seriously occurs for the tested steel after service. The major precipitation phase in the sample before service is M2 （C,N） metastable phase, and the dislocation density in the austenite is high, and reduces after service. Bulk-like M23 C6 phase and stripd σ phase precipitates on the grain boundary in the inside grains after long time service, respectively. Besides, the room-temperature and high-temperature strength, plasticity and toughness of the steel decrease after service.