不同氮含量电弧增材制造不锈钢点蚀和电化学腐蚀行为研究

Study on pitting and electrochemical corrosion behavior of stainless steel with different nitrogen content via wire arc additive manufacturing

关键词:  氮含量  电弧增材制造  粉芯丝材  双相不锈钢  腐蚀

Key words:  nitrogen content  wire arc additive manufacturing  metal-cored wire  duplex stainless steel  corrosion

摘要:

针对双相不锈钢电弧增材制造的需求,本文以3组不同氮含量粉芯型丝材电弧增材制造双相不锈钢,采用FeCl₃浸泡实验、电化学阻抗谱、极化曲线、SEM/EDS及XPS等方法,重点研究了氮含量对电弧增材制造不锈钢沉积金属耐腐蚀性能的影响。研究表明:随着氮含量的增加,电弧增材制造不锈钢沉积金属在FeCl₃溶液中的腐蚀速率降低；当氮含量(质量分数)为0.35%时,沉积金属的抗FeCl₃点蚀能力最佳。电化学腐蚀实验表明,当氮含量为0.35%时,电荷转移电阻大于其他2组试样,并且腐蚀电流密度最低,其耐腐蚀性最好。随着氮含量的增加,沉积金属表面的蚀坑不断减少,沉积金属的耐蚀性增加。氮含量的增加使沉积金属表面钝化膜中Cr₂O₃含量增加,而氢氧化物含量则减少；Cr₂O₃含量的增加能够有效增强钝化层的稳定性。

Abstract:

In order to satisfy the demand of duplex stainless steels via wire arc additive manufacturing, duplex stainless steels are fabricated by arc additive manufacturing of metal-core wire with different nitrogen content in this study. The effect of nitrogen content on the corrosion resistance of additive manufactured deposited metals is mainly studied through FeCl₃ immersion test, electrochemical impedance spectroscopy, polarization curves, SEM/EDS and XPS analysis.The results show that the corrosion rate of the deposited metals in FeCl₃ solution decreases with the increase of nitrogen content, and the resistance to FeCl₃ pitting of the deposited metals is the best with the nitrogen content of 0.35%.Electrochemical corrosion test indicates that the sample with nitrogen content of 0.35% exhibits the highest charge transfer resistance and the lowest corrosion current density, indicating superior corrosion resistance.Furthermore, with the increase of nitrogen content, the pits on the deposited metals decrease and the corrosion resistance of the deposited metals increases. The content of Cr₂O₃ in the passive films increases with the increase of nitrogen content,whereas the content of hydroxide decreases. The increase in Cr₂O₃ can effectively increase the stability of the passivation layer.