Fractography: Corrosion fatigue failure of a stainless steel stud

Instruments: FEI Nova200 NanoSEM, Philips XL-40 SEM-EDX

Techniques: SE/BEI imaging, EDX spectroscopy

Summary: The stud served in a chemical engineering environment and was subjected to pure torsion load. The fracture failure shows two crack initiations. The principal crack ‘I’ was caused by the combined inter-granular corrosion and the surface stress concentration. The subsequent propagation was caused by the applied torsion loads and progressive corrosion. The second crack ‘II’ was caused mainly by stress concentration after the reduction of load-bearing area. Its propagation was also driven by the applied torsion loads until the catastrophic failure.