Fracture failure analysis of 4Cr13 stainless steel linkages in circuit breakers

• Failure analysis of 4Cr13 stainless steel components was studied.
• Effect of heat treatment on mechanical properties of components was investigated.
• Fracture failure mode was quasi-cleavage fracture under overloading condition.

In this study, the fracture failure of the 4Cr13 stainless steel linkage components in circuit breakers was studied. The microstructure and morphology of fracture surface were observed by scanning electron microscopy and optical microscopy. A micro-Vickers tester measured the hardness of the components. The tensile strength and strain of the components were determined by a universal testing machine. The results show that fracture failure mode was quasi-cleavage fracture, and some dimples and edges of cleavage were present on the fracture surface. The substandard sample exhibited higher hardness than the standard sample. The high hardness could cause the strong rigidity and less toughness, which was not helpful to bend the samples to form hook structure. The heat treatment influenced the mechanical properties of the 4Cr13 components. With increasing the tempering temperature, the hardness of the component was decreased when the quenching temperature was kept stable.