Ni系低温钢的高温氧化行为研究

为研究Ni系低温钢的高温氧化行为，利用Setsys Evolution型高温同步热分析仪对Fe-3.5Ni和Fe-9Ni钢在700~1200℃的氧化行为进行了研究，采用电子探针(EPMA)、场发射扫描电镜(SEM)和X射线衍射(XRD)等手段表征了氧化物微观形貌和物相组成.结果表明:700~1200℃条件下氧化2h后，Fe-3.5Ni钢和Fe-9Ni钢的氧化增重曲线规律相似，相同氧化温度条件下，单位面积Fe-9Ni钢的增重量低于Fe-3.5Ni钢.随氧化温度的升高，试样表面依次出现团絮状、晶须状和不规则多边形状Fe₂O₃.氧化分为内氧化和外氧化，内、外氧化层厚度随氧化温度的提高逐渐增加，且900℃是两种钢外氧化层厚度发生突变的临界温度.内氧化层由FeNi₃和混合物(FeO+Fe₃O₄)组成，外氧化层由Fe₂O₃，Fe₃O₄和FeO组成，且外氧化层内包裹着尖晶石相NiFe₂O₄；随着Ni含量增加，NiFe₂O₄增多并形成连续的薄带.

High Temperature Oxidation Behavior of Ni-based Low Temperature Steel

The oxidation behavior of Fe-3.5Ni and Fe-9Ni at 700~1200℃ was investigated using Setsys Evolution high-temperature thermal gravimetric analyzer to study the high temperature oxidation behavior of Ni-based low temperature steel. The oxide morphology and phase composition were analyzed with electron-probe microanalyzer (EPMA)， scanning electron microscopy (SEM)， X-ray diffraction (XRD). The results show that the oxidation mass gain curves of Fe-3.5Ni steel and Fe-9Ni steel are similar after oxidation for 2h at 700~1200℃. Under the same oxidation temperature， the unit area mass gain of Fe-9Ni steel is lower than that of Fe-3.5Ni steel. As the oxidation temperature increases， agglomerate floc， whisker and irregular polygonal Fe₂O₃ appear on the surface of the sample. Further results indicate oxidation is divided into internal and external oxidation. As the oxidation temperature increases， the thickness of the external oxide layers and subscale gradually increases， and 900℃ is the critical point at which the thickness of the outer oxide layers of the two steels changes. The subscale compound consists of FeNi₃ and a mixture (FeO+Fe₃O₄). The external oxidation consists of Fe₂O₃， Fe₃O₄ and FeO， and the crystallite phase NiFe₂O₄ is encapsulated in the external oxide layer; as the Ni content increases， more NiFe₂O₄ is produced.