W对第三代单晶高温合金抗氧化性能的影响

Effect of W content on oxidation resistance of experimental third generation single crystal superalloy

摘要:

采用X射线衍射(XRD)，扫描电镜(SEM)及能谱(EDX)等方法研究了不同W含量的3种试验单晶高温合金在1100℃的恒温氧化行为。结果表明： 8%W合金氧化增重最大，6%与7%W的增重量相当，3种合金氧化动力学曲线近似遵从抛物线规律。试验合金氧化100h后氧化膜剥落严重，8%W含量试验合金表面氧化膜剥落较6%与7%W合金严重，氧化膜由3层构成：最外层主要为(Ni,Co)O；中间层主要为氧化物和尖晶石相；最内层是连续的A12O3层。在合金基体形成了γ''贫化层。在本合金体系下，随W元素含量变化，改变了试验合金1100℃氧化机制，在合金设计时，兼顾合金高温强度与抗氧化性能，应选择W含量不超过7%为宜。

Abstract:

The isothermal oxidation behaviors of three kinds of experimental third generation single crystal superalloys with different tungsten contents were investigated at 1100℃ in air by X-ray diffraction (XRD), scanning election microscopy (SEM) and energy disperse X-ray analysis (EDX). The experimental results showed that three kinds of alloys approximately obeyed subparabolic rate law during oxidation of 100h at 1100℃. The mass gains of 8wt. % W-containing alloy remained higher than the mass gains of 6 wt.% and 7wt.% W-containing alloys. The oxide scale exposed at 1100℃ was consist of three layers: an outer Ni(Co)O layer, an intermediate layer mainly composed of oxides and spinels, and an inner Al2O3 layer. The γ′-free layer was formed in the base alloy. In the current alloy system, the transition of oxidation mechanism happened with increasing W content at 1100℃, therefore, it was found that the alloys with a W content less 7% exhibited relative balance between oxidation resistance and solution strength.