Isothermal Oxidation Behavior of Ni-20Cr-18W Superalloy at 1100 oC

摘要:

利用电镜、具备能谱分析功能的扫描电子显微镜和X射线衍射仪等分析设备，研究了一种新型Ni-Cr-W基高温合金Ni-20Cr-18W在1100 oC的恒温氧化行为。通过试样的氧化增重，获得了氧化动力学规律。分析结果显示，在氧化初始阶段，合金表面生成了由六面体结构的Cr2O3，立方结构的NiO和与M3O4型氧化物同型的尖晶石结构 (Ni，Mn，Cr)3O4 3种相组成的混合氧化膜。长时间氧化后，氧化膜由单层转变为双层，在内层形成连续的Cr2O3膜，在外层形成可以抑制内层Cr2O3挥发的致密NiO氧化膜；同时在氧化膜与合金基体界面处形成氧化孔洞，并且在该处发生Al元素的内氧化

Abstract:

The isothermal oxidation behavior of a new Ni-Cr-W base superalloy Ni-20Cr-18W at 1100 oC has been investigated by analytical electron microscopy, scanning electron microscope coupled with energy dispersive spectrum and X-ray diffraction. Oxidation kinetics was evaluated from measurements of mass change, metal loss and internal penetration. Initially, the mixtural oxide scale is composed of hexagonal Cr2O3, cubic NiO and spinel-type (Ni，Mn，Cr)3O4 isomorphous with M3O4 at the initial stage of oxidation. After long-term oxidation, the oxide scale turns from mono-layer to double-layer. There is a consecutive Cr2O3 scale at inner adherent layer, and a compact NiO scale at outer layer which can restrain the inner Cr2O3 volatilization. At the same time, the oxidation void has formed between the oxide scale and interface of the alloy (scale/metal interface), and the inner oxidation of Al element happens at this place