海上钻具硬连接堵头应力腐蚀断裂失效分析.

A “hard-connection” plug of drilling tool fractured on an offshore operation platform, which involved the fracture of beryllium bronze hexagonal nut and superalloy shell. This paper focuses on finding out the first broken piece, the failure mode and failure mechanism. Through the macro analysis of fracture, observation of micro morphology and EDS, microstructure and microhardness measurement, it is determined that the fracture of beryllium bronze hexagonal nut is caused by stress corrosion fracture and it causes one-time ductile fracture of the shell. The abnormal structure of beryllium bronze hexagonal nut, which caused by over aging heat treatment, leads to grain boundary reaction and reduces the mechanical properties of the material. It is the main reason for the stress corrosion fracture of hexagonal nut. The corrosion pit on the inner surface of hexagonal nut and stress concentration formed by machining knife mark are the inducing factors of stress corrosion fracture. [ABSTRACT FROM AUTHOR]