高温过热器T91/TP347H异种钢焊接接头早期失效分析OA

In response of the cracking and failure problem of heterogeneous steel welding joint of T91/TP347H in a 1 000 MW ultra-high temperature superheater of a certain power plant,methods such as chemical composition analysis,microstructure observation and mechanical property testing were adopted to analyze the failure causes.The results show that the weld size of T91/TP347H heterogeneous steel,the chemical composition of the base metal on both sides,and the tensile strength of the joint all meet the standard requirements.The microstructure on the T91 side of the welding joint is lath martensite,the weld is γ-Ni austenite,and the TP347H side is γ-Fe austenite.There is an oxide layer 87 to 89.51 μm thick on the inner and outer walls of the T91 side.Oxidation notches and cracks are observed at the weld interface of T91/TP347H,with a large amount of M23C6 second phase rich in C,Cr,Mo,Ni,and V and creep voids concentrated at the crack tip.The peak hardness of the heat affected zone on the T91 side is 331 HV1.0,which exceeds the standard value.The main cause of the failure of the T91/TP347H heterogeneous steel welding joint is the improper post-weld heat treatment process of the joint itself,which leads to a relatively high hardness in the heat affected zone.Coupled with the complex superimposition and synergy of welding stress and service stress at the heterogeneous steel interface,as well as the creep of the material itself during long-term high-temperature service,the early failure of the heterogeneous steel joint is ultimately caused.