热冲压成形SAF2507 SDSS在不同溶液中耐点蚀性能

 为了研究SAF2507 SDSS热冲压成形后在不同服役环境中阴离子对耐点蚀性能的影响,对SAF2507 SDSS板材进行1 050 ℃热冲压成形,使用ZEISS-SUPRA55型扫描电镜观察微观组织并测定相组织能谱,运用动电位极化曲线、开路电位和交流阻抗谱手段研究SAF2507 SDSS在3.5%质量浓度的NaClO和卤化钠NaX(X=Cl、Br、I)溶液中的耐点蚀性能。结果表明,SAF2507 SDSS在1 050 ℃热冲压成形后微观组织良好,α/γ体积比约为1∶1,α相富铬、钼贫镍电极电位低,为阳极,γ相富镍贫铬、钼电极电位高,为阴极;在4种溶液中,耐点蚀性能从高到低为NaClO、NaCl、NaBr和NaI,NaClO溶液中点蚀坑数量最少,蚀坑小而浅,NaI溶液中点蚀坑数量最多,蚀坑大而深;ClO-对点蚀形核和生长阶段起到抑制作用,Cl-、Br-和I-只在点蚀形核阶段起到促进作用,促进作用从大到小为I-、Br-和Cl-。

Pitting corrosion resistance of hot stamping forming SAF2507 SDSS in different solutions

In order to research the influence of anions on pitting corrosion resistance of SAF2507 SDSS after hot stamping forming in different service environments,SAF2507 SDSS plates were subjected to hot stamping forming at 1 050 ℃. The phases and chemical composition were observed and tested by using ZEISS-SUPRA55 scanning electron microscope and energy dispersive spectrometer. The pitting corrosion resistance of SAF2507 SDSS in 3.5% NaClO and sodium halide (NaX,X=Cl,Br,and I) solutions by mass were investigated by means of potentiodynamic polarization curves,open circuit potentials and AC impedance spectroscopy. The results show that the microstructure of SAF2507 SDSS of hot stamping forming at 1 050 ℃ is favorable and the volume ratio of α/γ is about 1∶1. The potential of α phase which is riched in Cr,Mo and depleted in Ni is lower than γ phase as the anode during the corrosion process. In four aggressive solutions,the pitting corrosion resistance from high to low is NaClO,NaCl,NaBr,and NaI. The number of pitting cavities in the NaClO solution are least,and the size of pitting cavities are small and shallow. In contrast,The number of pitting cavities in the NaI solution are maximum and the size of pitting cavities are large and deep. The ClO- ions inhibit the nucleation and growth of pittings and the Cl-,Br-,and I- ions only promote the nucleation of pittings,and the influence from high to low is I-,Br-,and Cl-.