时效温度对15-5PH不锈钢组织及耐蚀性的影响

Effect of Aging Temperature on Microstructure and Corrosion Behavior of 15-5PH Precipitation Hardened Stainless Steel

对15-5PH不锈钢经不同温度时效后的结构及耐蚀性进行研究。利用金相显微镜、XRD、SEM及TEM观察其组织并对相结构进行分析;采用化学浸泡、极化曲线和电化学阻抗谱等方法研究其耐蚀性能。结果表明:随时效温度的增加马氏体组织逐渐细化,马氏体板条间析出NbC颗粒;当时效温度达到550℃时有球状富Cu相析出。580℃开始有较弱的奥氏体衍射峰出现,即在时效中发生了马氏体向奥氏体的逆转变,620℃时,富Cu相由共格相转变为非共格相并聚集长大呈短棒状;随着时效温度的升高,腐蚀失重率逐渐增大,自腐蚀电位依次降低,电化学阻抗值不断减小,耐蚀性降低。

The effect of aging treatment temperature on the evolution of the microstructure and corrosion resistance of 15-5PH stainless steel was studied by means of XRD, SEM and TEM as well as immersion test and measurements of polarization curve and electrochemical impedance spectroscopy. The results show that the martensitic structure of the steel is gradually decomposed to be finer with the increase of aging temperature, while NbC particles precipitate in between martensitic laths. Spherical particles of Cu-rich phase is separated out at aging temperature 550 ℃. Austenite was observed at 580 ℃ implying the reverse conversion from martensite to austenite occurs due to over ageing. With the increase of aging temperature, the Cu-rich phase change into coherent from incoherent, which gathered to growth as short rod at 620 ℃; the corrosion weight loss rates increase; the corrosion potential decrease; Ac impedance values reduced and therefore the corrosion resistance of the steel degraded.