深冷处理后回火温度对15Cr超级马氏体不锈钢组织及耐点蚀性能的影响

利用场发射扫描电镜、透射电镜以及电化学综合测试系统对15Cr超级马氏体不锈钢(SMSS)经不同热处理工艺处理后的显微组织变化和第二相碳化物及其对该钢腐蚀行为的影响进行了研究。结果表明,试验钢经不同热处理工艺处理后组织均由板条马氏体、奥氏体以及M₂₃C₆型碳化物颗粒组成,随着回火温度的增加,试验钢中逆变奥氏体含量增加,且在650 ℃回火时达到体积分数最大值41.41%。当回火温度高于600 ℃时第二相碳化物开始析出,且650 ℃回火后碳化物数量及尺寸较600 ℃增多。点蚀电位随着回火温度的增加而降低,第二相碳化物的析出降低了试验钢的点蚀电位,促进了亚稳点蚀位置的形成,从而降低了试验钢的耐腐蚀性能。

Effects of tempering temperature after cryogenic treatment on microstructure and pitting resistance of 15Cr super martensite stainless steel

Microstructure evolution and second phase carbides of 15Cr super martensitic stainless steel (SMSS) treated by different heat treatment processes and their influence on the corrosion behavior were investigated by means of field emission scanning electron microscope (SEM), transmission electron microscope (TEM) and electrochemical comprehensive testing system. The results show that the microstructure of the tested steel are composed of martensite, austenite and M₂₃C₆ carbides after different heat treatment processes. With the increase of tempering temperature, the volume fraction of reversed austenite in the tested steel increases and reaches a maximum value of 41.41% at 650 ℃. The second phase carbides appear when the tempering temperature is higher than 600 ℃, besides, the quantity and the size of carbide after tempering at 650 ℃ are larger than that at 600 ℃.The pitting potential decreases with the increase of tempering temperature, the precipitation of carbides reduces the pitting potential of the stainless steel, promotes the formation of metastable pitting, and reduces the corrosion resistance of 15Cr stainless steel.