GH4720Li合金高温氧化行为研究

Study on Oxidation Behavior of Alloy GH4720Li at High Temperatures

采用静态增重法测定了GH4720Li合金在650～900℃的氧化动力学，并利用SEM、EDS和XRD手段分析了不同温度下氧化膜的组成及结构，据此对GH4720Li合金的氧化机制进行了研究。结果表明，GH4720Li合金在900℃以下属完全抗氧化级。750℃以下，GH4720Li合金的氧化速率随温度升高缓慢增加，氧化膜主要由（Cr0.88Ti0．12）2O3和Cr2Nio4组成；超过750℃，合金的氧化速率显著增加，氧化层主要由（Cr0.88Ti0.12）2O3和TiO2组成。Ti的含量沿氧化层厚度方向由里向外逐渐增加，而Cr的分布规律正好相反。合金氧化动力学遵循抛物线规律，氧化机制由初始表面生成反应控制转变为扩散机制控制。

The high temperature oxidation behavior of alloy GH4720Li has been studied using static weight increment method. Scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS） and X-ray diffraction （XRD） techniques were used to characterize the composition and structure of the oxides at different temperatures. Accordingly, oxidation mechanism of alloy GH4720Li is investigated. The results show that alloy GH4720Li belongs to entirely inoxidizable calss under 900℃. When temperature is under 750℃, oxidation rate increases slowly with temperature elevation and the main oxidation products are （Cr0.88 Ti0.12 ）2 03 and Cr2 NiO4. When tempera- ture is above 750 ℃, oxidation rate increases remarkably and the main oxidation products are （Cr0. 88Ti0. 12 ）2O3 and TiO2. The content of titanium increases slowly along the thickness direction of oxide layer from inside to outside. But the distributing of chromium is contrary to titanium. The oxidation kinetics obeys parabola law. Oxidation mechanism changes from surface reaction t diffusion mechanism.