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 stainless steel with both homogenized and aged microstructures has been studied using the single edge notched specimens tested in 3.5% NaCl solution. 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 aging treatment and the resistance increases evidently with increasing the W content. The higher extrinsic CFCG resistance in the aged microstructure is attributed to the roughness-induced crack closure, due to the brittle fatigue failure along the precipitation-weakened grain boundaries. The intrinsic CFCG resistance mainly results from the decrease in the corrosion rate by moderating the Cr depletion due to the addition of W that suppresses the precipitation of sigma phase.