研究了固溶处理制度对不同变形量下的AISI 304奥氏体不锈钢晶间腐蚀性能的影响规律。采用室温单向拉伸实验获取了不同变形量下的AISI 304不锈钢试样,通过XRD测量了其中由于形变诱发的马氏体相的含量,采用电化学动电位再活化法(EPR)研究了固溶处理温度及时间对不同变形量下AISI 304不锈钢晶间腐蚀的影响。实验结果表明,AISI 304不锈钢晶间腐蚀程度随着变形量的增加而提高,而随着固溶处理温度和时间的增加而降低。其原因是由于AISI 304不锈钢形变诱发马氏体相变行为所引起的微观组织变化及其导致的固溶处理初期C元素的偏聚在不同固溶条件下的回复程度不同,从而对后续晶间腐蚀性能产生显著影响。
AISI 304 austenite stainless steel was applied extensively in the modern industry due to its good properties on mechanics and corrosion resistance. However, there is severe intergranular corrosion when the AISI 304 was working at the temperature 420~850 ℃ called sensitizing temperature. This phenomenon was more obvious with increase of strain. In addition, this effect can not be removed completely even with the heat treatment subsequently. In present work, the influence of solution treatment and plastic deformation on the intergranular corrosion property of AISI 304 was investigated. The specimens subjected to different strain were obtained by the uniaxial tensile tests at room temperature. XRD was used to measure the fraction of martensitic phase which was induced by deformation. Optical metal lographic microscope was applied to observe the evolution of microstructure. The influence of various deformation values, solution temperature and holding time on intergranular corrosion was quantitative analyzed by electrochemical potentiodynamic reactivation (EPR) method. Experimental results showed that the degree of the intergranular corrosion increased with the increase of deformation, and with the decrease of solution temperature and holding time. It is indicated that since the solubility of carbon in martensite and austenite is discrepant, the content of carbon in the grains recrystallized is discrepant too. The more martensite is transformed, the more chromium carbide is formed in the grain boundary after sensitization. This phenomenon causes poor intergranular corrosion resistance due to the lack of chromium. In addition, the carbon segregation which is caused by plastic deformation will relieve with the rise of solution temperature and holding time. It is because that the carbon atom is more active at higher temperature, and the distribution of carbon is more homogeneous with the extended holding time. Then the quantity of chromium carbide will decrease in solution treatment process. Consequently the chromium depletion will be mitigated. From the above, a uniform solution treatment condition is not suitable for austenite stainless steel with the effect of martensitic transformation in cold working. Flexible scheme can be employed to insure better combination property of products.
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