摘要
某电厂锅炉屏式过热器在运行8万h后,其T91/TP347H异种钢接头出现沿晶裂纹,裂纹位于TP347H奥氏体钢侧热影响区。通过显微组织观察、硬度测试和拉伸试验分析了沿晶开裂的特征、形成原因及其对力学性能的影响。结果表明:沿晶裂纹出现在TP347H钢侧熔合线处,为晶间腐蚀裂纹,裂纹深3~4个晶粒尺度,内部有氧化物填充;存在沿晶裂纹的屏式过热器管接头的硬度和抗拉强度符合标准要求,但塑性较差;粗大的晶粒和焊后较快的冷速使得屏式过热器管接头TP347H钢侧热影响区在高温服役过程中易发生晶界贫铬,引发晶间腐蚀,TP347H钢侧熔合线附近较高的硬度梯度导致应力易在此处集中,从而加速晶间腐蚀裂纹的产生。
Intergranular cracks were found in T91/TP347 H dissimilar steel joint of a boiler panel superheater in a power plant after 80 000 h operation. The cracks were located in the heat-affected zone on TP347 H austenitic steel side. The features and forming causes of the intergranular cracking and its effect on the mechanical properties were analyzed by microstructure observation, hardness test and tensile test. The results show that the intergranular cracks existed at the fusion line on TP347 H steel side, and were intergranular corrosion cracks. The cracks penetrated through 3-4 grains and were filled with oxides inside. The hardness and tensile strength of the panel superheater tube joint with intergranular cracks met the requirements, but the plasticity was poor. Coarse grains and fast cooling rates after welding made the heat affected zone on the TP347 H steel side of the panel superheater tube joint prone to forming depletion of chromium at grain boundaries during high-temperature service, causing intergranular corrosion. The high hardness gradient near the fusion line on the TP347 H steel side led to stress concentration here, accelerating the generation of intergranular corrosion cracks.
作者
李勇
LI Yong(Datang Boiler Pressure Vessel Inspection Center Co.,Ltd.,Hefei 230088,China;East China Electric Power Test and Research Institute,China Datang Corporation Science and Technology General Research Institute Ltd.,Hefei 23088,China)
出处
《机械工程材料》
CAS
CSCD
北大核心
2022年第7期82-89,共8页
Materials For Mechanical Engineering
