Correlation of meso- and micro-scale hardness measurements with the pitting of plastically-deformed Type 304L stainless steel

Short lengths of circular section Type 304L stainless steel were cut from a pipe and compressed into an oval shape using controlled conditions. Heterogeneous strain hardening in the range 0–25% was thus introduced into the material. The mechanical deformation process was modelled using ABAQUS finite element modelling software to calculate the distributions of strain hardening and residual stress throughout a typical specimen. Samples were then exposed to an environment intended to induce pitting over the surfaces. Correlation between the computer model and the observed pitting was obtained. Finally, micro- and meso-scale hardness measurements were made on similarly deformed specimens and found to correlate well with the FE results. It was concluded that pitting was associated with regions of greatest equivalent plastic strain and showed little relation to the regions of high tensile residual stress. An empirical relationship between the Vickers Hardness number and the equivalent plastic strain is determined.