Failure Analysis and Finite Element Simulation on Service Conditions of SUS304 Stainless Steel

The purpose of this paper was to study the failure behavior of SUS304 stainless steel in view of cooling water leakage in actual service conditions. The temperature field and thermal stress distribution in the thickness direction of SUS304 stainless steel under actual service conditions were further analyzed by the finite element method. The results show that chromium-rich carbides are precipitated at the grain boundaries, which may cause intergranular corrosion. The morphology of the corrosion grooves is ditch structure, which has high intergranular corrosion susceptibility. The expansion direction of the cracks is from the contact surface of cooling water to the high-temperature contact surface. Fracture is characterized by a river pattern and rock candy pattern. Fracture morphology is characterized by brittle rupture. The Cl contained in the corrosion products comes from the circulating cooling water. XRD patterns show that the corrosion products are composed of CaCO3 (the high-temperature contact surface) and Fe3O4 (the contact surface of cooling water), respectively. EDS results of corrosion products are consistent with XRD results. The results of finite element simulation show that the temperature field along the thickness direction of SUS304 stainless steel plate is in the range of 436.6-450 °C. The peak of thermal stress is located in the middle of cross section. The cause of failure is acceleration of the initiation and extension of the cracks under the combined action of chloride ion stress corrosion, intergranular corrosion, and thermal stress. The form of crack fracture is mixture of transgranular and intergranular fracture, mainly transgranular fracture, which belongs to typical chloride ion stress corrosion.