Understanding the combined effect of decreasing C contents and increasing solid-solution time on intergranular corrosion resistance of 304 austenitic stainless steel

The purpose of this study is to investigate the intergranular corrosion resistance mechanism of 304 austenitic stainless steel treated by the combination effect of decreasing C contents and increasing the solid-solution treatment time. The findings indicate the combination effect of decreasing C contents and increasing the solid-solution treatment time effectively limits the intergranular corrosion behavior of the steel within an acceptable range (degree of sensitization, DOS values < 1). On the one hand, reducing the carbon content in the 304 austenitic stainless steel leads to insufficient levels of carbon that is necessary to reach the critical value for Cr-carbide nucleation, which decreases the occurrence of Cr-depleted zones. In comparison, the intergranular corrosion tendency of 304 austenitic stainless steel decreases at higher solid-solution temperatures and for longer treatment times, and its main purpose is to reduce the occurrence of large-sized Cr-carbide and its pinning effect on the grain boundaries. Moreover, the reduction in grain boundaries due to the grain growth further constrains the intergranular corrosion behavior of 304 austenitic stainless steel, which provides strong support for further optimizing the process conditions and reducing the failure caused by intergranular corrosion.