The effect of δ-ferrite on fatigue cracks in 304L steels

Continuous low-cycle fatigue tests of 304L stainless steel at 300 and 600°C and Δεt=±2.0% in an air environment were conducted, and the effects of the amount and direction of δ-ferrite stringers on fatigue crack initiation and fatigue life were investigated. Fatigue crack initiation was observed at the interface between δ-ferrite and a particulate matrix. The effect of δ-ferrite in 304L stainless steel on fatigue life in low-cycle fatigue was investigated. 304L stainless steel with δ-ferrite perpendicular to the loading axis has a much shorter fatigue life than that with δ-ferrite parallel to the stress axis. These phenomena are thought to be caused by the strain incompatibility at the interface between δ-ferrite and the matrix.