奥氏体耐热钢中的纳米析出相研究

Study on Nano Precipitated Phase in Austenitic Heat Resistant Steel

采用扫描电镜、透射电镜和X-射线衍射仪研究了固溶处理后不同温度时效处理对25Cr-20Ni-Nb N奥氏体耐热钢显微组织和性能的影响。结果表明,试验钢经过1150℃固溶处理后的显微组织为奥氏体基体内分布粗大颗粒状Nb Cr N相（Z-相）;在650～900℃时效处理1 h后,在奥氏体晶界上析出M23C6型碳化物;在850℃时效1 h后,除在奥氏体晶界上析出M23C6型碳化物外,还在奥氏体晶粒内部析出均匀分布的纳米尺寸Z-相,纳米尺寸Z-相的颗粒密度达到每平方微米7.8个;试验钢的硬度随时效温度的升高先降低后升高再降低,在850℃时达到最大值,硬度的变化与纳米尺寸的Z-相析出强化有关。

The effects of different temperature aging treatment on the microstructure and properties of 25Cr-20Ni-NbNaustenitic heat resistant steel alter solution treatment at 1150 ℃ were investigated by scanning election microscopy,transmission election microscopy and X-ray diffractometer. The results show that after solution treatment at t 150 ℃, themicrostnlcture of the test steel is a coarse granular NbCrN phase （Z-phase） distributed in the austenite matrix; M.,3C6 carbidesprecipitates on austenite grain boundary after aging treatment at 650-900℃ for lh; after aging at 850 ℃ for I h, in addition tothe precipitation of Mz℃ type carbide on the austenite grain boundary, the austenite grains precipitate the uniform distributionof nanometer sized Z-phase, and the particle size of the nanometer size Z-phase reaches to 7.8 number/Ixm2; the hardness ofthe test steel firstly decreases then increases and then decreases with the increase of aging temperature, which reaches themaximum value at 850 ℃, and the change of hardness is related to the precipitation enhancement ofnanometer size Z-phase.