Experimental study on mechanical properties and low-cycle fatigue behaviour of stainless steels subjected to salt spray and dry/wet cycle

This paper presents experimental studies on the mechanical properties and low-cycle fatigue behaviour of corroded austenitic stainless steel (3 0 4) and ferritic stainless steel (4 3 0). Tensile and low-cycle fatigue tests are conducted on 28 specimens. The corrosion process of the specimens is finished by using salt spray and dry/wet cycle tests. In the tensile tests, the key parameters of the constitutive model proposed by both Rasmussen and Gardner were obtained for austenitic stainless steel (3 0 4) and ferritic stainless steel (4 3 0). In the low-cycle fatigue test, the relationships of the stress amplitude and fatigue life of the specimens were obtained. The relationships of the mass loss, corrosion rate and cross-sectional area loss with the corrosion time are established. The influences of corrosion pits and fatigue cracks on the low-cycle fatigue behaviour of these two materials are studied through both macro and micro fracture morphology analysis. It is found that compared with the salt spray, the dry/wet cycle condition causes more degradation on the strength and fatigue life of the ferritic stainless steel (4 3 0). The stress concentration and notch effect of corrosion pits are the main reasons for the degradation in fatigue life of ferritic stainless steel (4 3 0). Moreover, current codes Eurocode 3 (EC3), Australian Standard (AS), BSI Standard (BSI) and DNV Standard (DNV) could not provide accurate fatigue life assessment for these two materials after salt spray and dry/wet cycle corrosions.