S31609奥氏体不锈钢中残留δ铁素体的腐蚀行为

对含残留δ铁素体的S31609奥氏体不锈钢进行650 ℃、保温2h的敏化处理,通过金相蚀刻、电子探针和扫描开尔文探针显微镜分析并比较残留δ铁素体和奥氏体晶界处的腐蚀特征.结果表明,随着敏化过程中残留δ铁素体快速分解成稳定的σ相、二次奥氏体(γ2)和Cr23C6,尽管奥氏体晶界和δ/γ相界处没有明显的Cr/Mo贫化区,但...

Influence of delta-ferrite on corrosion behavior of S31609 austenitic stainless steel

The S31609 austenitic stainless steel containing residual delta-ferrite was sensitized at 650 ℃ for 2 h. The corrosion characteristics of residual delta-ferrite and austenite grain boundary were analyzed and compared by metallographic etching, electron probe microanalyzer and scanning Kelvin probe. The results show that the residual delta-ferrite is rapidly decomposed into sigma phase, secondary austenite phase (γ₂) and Cr₂₃C₆ during the sensitization process. Although there is no obvious Cr and Mo solute depleted zone at austenite grain boundary and δ/γ grain boundary, the potential difference between the precipitated phase and the adjacent substrate always exists. The Fermi energy of the secondary phase, such as the sigma phase, γ₂ and Cr₂₃C₆is lower than that of the matrix, which makes it easier for electrons to jump from the Fermi surface of the surrounding matrix. As a result, the matrix acts as an anode in the electrochemical corrosion system, and the corrosion occurs preferentially.