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采用X射线衍射(XRD),扫描电镜(SEM)及能谱(EDX)等方法研究了不同钴含量的两种镍基单晶高温合金在900,1000和1100℃的恒温氧化行为。研究发现,增加合金中的Co含量,会降低合金的扩散激活能,引起氧化速率的略微增加。在900和1000℃氧化时符合抛物线规律,氧化膜分为3层:外层主要由Cr2O3和TiO2组成;中间层是很薄的CrTaO4和Ta2O5氧化层;内层是连续的Al2O3氧化层。在1100℃时氧化膜的严重剥落和CrO3的挥发使增重曲线略微偏离抛物线规律,生成了NiCr2O4,CoAl2O4,CoNiO2和Co2TiO4等尖晶石相,并发生了内氮化。
The isothermal oxidation behavior of two kinds of nickel-base single crystal superalloys with different cobalt contents at 900, 1000 and 1100 ℃ was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDX) The study found that increasing the Co content in the alloy decreases the diffusion activation energy of the alloy and causes a slight increase in the oxidation rate. Parabolic law at 900 and 1000 ℃, the oxide film is divided into three layers: the outer layer is mainly composed of Cr2O3 and TiO2; the middle layer is very thin CrTaO4 and Ta2O5 oxide layer; the inner layer is continuous Al2O3 oxide layer. At 1100 ℃, the severe exfoliation of the oxide film and the volatilization of CrO3 led the curve of the weight gain to deviate slightly from the parabolic law. The spinel phases such as NiCr2O4, CoAl2O4, CoNiO2 and Co2TiO4 were formed and nitrided.