时效温度对节镍双相不锈钢S32101晶间腐蚀行为影响的研究

Effects of Aging Temperature on Intergranular Corrosion Behavior of S32101 Lean Duplex Stainless Steel

采用金相显微镜(OM)、显微硬度仪、电化学动电位再活化法(EPR)和电化学阻抗谱(EIS)对不同温度时效态S32101节镍双相不锈钢的显微组织、显微硬度和耐蚀性进行研究。结果表明:随时效温度从300℃升高,显微硬度增加,钝化膜致密性和耐蚀性下降;700℃时,相界处出现明显析出相,为碳氮化物和二次奥氏体组成的混合相,显微硬度达最大,钝化膜致密性和耐蚀性最差,几乎整个铁素体相被腐蚀,腐蚀机理是铁素体相的选择性溶解;继续升高到900℃,析出相减少,硬度下降,钝化膜致密性变好,耐蚀性提高。

The microstructure,microhardness and corrosion resistance of S32101 lean duplex stainless steel after aging treatment at temperatures in a range from 300 ℃ to 900 ℃ were characterized by means of optical microscope（OM）, microhardness testers, electrochemical potentiodynamic reactivation（EPR）, electrochemical impedance spectroscopy（EIS）. The result showed that with the increasing aging temperature, the hardness increased, the passivation film would become uneven and less dense, so the corrosion resistance relative declined. When the aging temperature was700 ℃, obvious precipitates occurred at the phase boundaries, which were a mixture of carbon or nitride and secondary austenite; while the microhardness reached a maximum and the compactness of passivation film was worst, thereby, the corrosion resistance became worst; correspondingly corrosion occurred on nearly entire the ferrite phase in the steel, which indicated that the corrosion mechanism was a selective dissolution of ferrite phase. As the aging temperature raised up to900 ℃, the number of precipitates reduced, the microhardness decreased, the passivation film would become dense and the corrosion resistance was enhanced.