Failure behaviour of cladding made from Sv 07Kh25N13 austenitic stainless steel

Abstract

Sv 07Kh25N13 is austenitic stainless steel used in nuclear industry. Due to its excellent corrosion resistance in the environment of WWER type nuclear reactor primary circuit, it is applied as anticorrosive cladding of the reactor pressure vessel. In this paper, results of detailed experimental research of failure behaviour of the cladding are presented. Static fracture toughness values J0.2 exhibited an extreme scatter. Metallographic analysis performed on the fractured specimens revealed large variations of structure within every single cladding layer. Fractographic analysis performed on fracture surfaces revealed considerable variations of micromechanisms taking place during ductile crack propagation. Conclusions on the relationship between the local microstructure, the failure mode and the fracture toughness of the cladding were drawn. Results indicate that the fracture toughness of the cladding was primarily determined by local amount of sigma phase in the area of crack propagation.