Combined Effects of Pre‐Strain and Sensitization on Corrosion Fatigue Behavior of Type 304 Stainless Steel

Metastable austenitic stainless steel Type 304 was subjected to pre‐straining and/or sensitization heat treatment. The effects of pre‐strain and sensitization on corrosion fatigue behavior were investigated, as well as their combined effects. In laboratory air, the pre‐strained materials exhibited higher fatigue strengths than the un‐strained ones because of the strain hardening induced by strain‐induced martensitic transformation. Fatigue strengths of the sensitized materials were higher than those of un‐sensitized ones, where the fatigue strengths of both pre‐strained and sensitized ones were the highest. Pre‐straining and sensitization individually had detrimental effects on corrosion fatigue behavior in 3% NaCl solution. Additionally, the corrosion fatigue strength was the lowest in pre‐strained and sensitized materials, where the combined effects were seen. The combined reduction exceeded simple superposition, indicating a mutually enhancing interaction. This severe degradation stems from simultaneous crack initiation via pitting at strain‐induced martensite and intergranular cracking at the Cr‐depleted grain boundaries.