EFFECTS OF W ADDITION AND HEAT-TREATMENT ON CORROSION-FATIGUE CRACK-GROWTH BEHAVIOR OF DUPLEX STAINLESS-STEELS

The corrosion fatigue crack growth (CFCG) behavior of a duplex stainle ss steel with both homogenized and aged microstructures has been studi ed using the single edge notched specimens tested in 3.5% NaCl solutio n. The emphasis is put on the effects of the substitution of W for Mo and the isothermal aging treatment on the CFCG properties. It is found that the apparent CFCG resistance is markedly improved after the agin g treatment and the resistance increases evidently with increasing the W content. The higher extrinsic CFCG resistance in the aged microstru cture is attributed to the roughness-induced crack closure, due to the brittle fatigue failure along the precipitation-weakened grain bounda ries. The intrinsic CFCG resistance mainly results from the decrease i n the corrosion rate by moderating the Cr depletion due to the additio n of W that suppresses the precipitation of sigma phase.