Alloy Design to Prevent Intergranular Corrosion of Low-Cr Ferritic Stainless Steel with Weak Carbide Formers

Effect of weak carbide formers, Mo, Mn and Si, on intergranular corrosion (IGC) of low-Cr ferritic stainless steel is analyzed after IGC test using TEM and three dimensional atom probe. The co-addition of Mo, Mn and Si to low-Cr ferritic stainless steel effectively prevents IGC by forming along grain boundaries CMn 4 MoSi intermetallic compounds, which act not only as carbon trap sites but also as diffusion barrier against solute Cr diffusion toward grain boundaries. The low solubility of Cr in the CMn 4 MoSi intermetallic compound results in replenishing Cr in the Cr-depleted area.