S31254超级奥氏体不锈钢析出相演变及微观表征

利用热力学计算了S31254超级奥氏体不锈钢在500~1 200 ℃温度范围内的平衡态析出相,并结合热模拟试验、扫描电镜、透射电镜等方法,对不同析出物的析出行为进行了表征和分析。结果表明,S31254不锈钢奥氏体基体中可存在的第二相包括σ、χ、Laves等金属间相,Cr₂N、π型氮化物相以及M₂₃C₆型碳化物相,高Mo、高N、高Cr含量是该钢析出相种类复杂的主要原因;试验钢具有高的第二相析出倾向,σ相开始析出温度约为1 150 ℃,而在900~800 ℃区间可发现χ相和σ相的转变,χ相更易作为一种稳定相存在;析出相的析出位置和形貌呈现不同特点,晶界析出主要为σ相、χ相和Laves相,而晶内主要有呈针状和块状分布的χ相和呈棒状析出的Cr₂N相。

Evolution and microstructure characterization of precipitate phases in S31254 super austenitic stainless steel

The equilibrium precipitates of S31254 super austenitic stainless steel in the temperature range of 500-1 200 ℃ were calculated by thermodynamics. The precipitating behavior of different precipitates were characterized and analyzed by thermal simulation test, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and other methods. The results show that the second phases in the austenitic matrix of S31254 stainless steel include intermetallic phases such as σ, χ and Laves, Cr₂N, π-type nitride phases and M₂₃C₆ type carbide phases. The high Mo, high N and high Cr contents are the main reasons for the complexity of precipitates. The experimental steel has a high tendency to precipitate the second phase. The initial precipitation temperature of σ phase is about 1 150 ℃, and the conversion of χ phase and σ phase can be found in the range of 900-800 ℃. The χ phase is more likely to exist as a stable phase. The location and morphology of precipitates are different. The grain boundary precipitates are mainly σ phase, χ phase and Laves phase, while the intergrain precipitates are mainly acicular and massive χ phase and rod-shaped Cr₂N phase.