GH3535合金高温氧化性能研究

发布时间：2018-06-01 05:14

本文选题：GH3535镍基合金 + 氧化动力学　；参考：《重庆交通大学》2015年硕士论文

【摘要】：镍基高温合金由于具有较高的高温强度、良好的韧性、优越的耐腐蚀和抗氧化能力,在化工、石油和核工业等领域得到了广泛地应用。在2011年启动的中国科学院战略性先导科技专项《未来先进核裂变能》中,已将Ni-Mo-Cr系合金选定为钍基熔盐堆的关键结构材料。GH3535合金为我国自主研制的专门用于钍基熔盐堆的一种镍基高温合金,其化学成分与Hastelloy N合金非常接近。现阶段GH3535合金仍处于研制起步阶段,其在高温环境中的抗氧化性能优劣,将直接影响熔盐反应堆的使用安全及运行寿命。本文选用GH3535合金为研究对象,开展了GH3535合金700-980℃温度范围的恒温氧化实验和650℃与700℃循环氧化实验。采用扫描电镜(SEM)、X射线衍射分析(XRD)、电子探针(EPMA)和同步辐射X射线荧光技术(XFR)等多种现代分析测试手段,研究了氧化温度、氧化时间和氧化方式对GH3535合金氧化膜的形貌特征、氧化层深度、氧化物/基体界面元素分布的影响,探讨了高温氧化过程,揭示了GH3535合金的高温氧化机理。实验结果表明,GH3535合金在700℃经过2000小时的恒温氧化后,增重结果为1.642mg/cm2,氧化动力学曲线遵循立方规律,属于完全抗氧化等级。870℃和980℃恒温氧化时,由于温度提高导致氧化膜出现开裂和剥落现象,增重明显,分别为0.73mg/cm2和2.00mg/cm2,由合金抗氧化等级评定,870℃属于完全抗氧化,而980℃则属于抗氧化等级。700℃恒温氧化2000h后GH3535合金的氧化膜厚度为4-6μm,且具有明显的分层结构,外层主要是Ni O和Ni Fe2O4等复合氧化物,内层则为Cr2O3、Mo O2和Ni Cr2O4等混合氧化物,无明显内氧化现象;870℃恒温氧化100h后氧化膜厚度为10μm左右,氧化膜连续程度变差;980℃氧化100h后外层氧化膜出现剥落,露出内层氧化膜,并伴有内氧化孔洞产生。温度进一步提高,Cr,Mo易形成挥发性物质而导致合金的抗氧化性能下降。在650℃和700℃,分别对GH3535合金进行了1000次循环氧化实验。实验过程中没有出现失重现象,合金表面也没有出现明显剥落或肉眼可观察到的孔洞。氧化动力学曲线仍基本遵循立方规律。650℃循环氧化后表面氧化颗粒细小且没有形成尖晶石结构的氧化膜,700℃循环氧化时表面已形成了具有尖晶石结构的致密氧化膜。以上结果表明GH3535合金在650℃和700℃具有良好的抗氧化性能,有望在钍基熔盐堆中长期使用。
[Abstract]:Nickel based superalloy has been widely used in the fields of chemical, petroleum and nuclear industry because of its high high temperature strength, good toughness, excellent corrosion resistance and anti-oxidation ability. In the strategic pilot project of China Academy of Sciences in 2011, the Ni-Mo-Cr alloy has been selected as thorium base melt. .GH3535 alloy, the key structural material of the salt reactor, is a nickel base superalloy specially developed for thorium based molten salt reactor in China. The chemical composition of the alloy is very close to that of the Hastelloy N alloy. At the present stage, the GH3535 alloy is still in the initial stage of development. The oxidation resistance of the alloy in the high temperature environment will directly affect the production of the molten salt reactor. In this paper, the GH3535 alloy was selected as the research object, and the temperature range of GH3535 alloy at 700-980 C was carried out at constant temperature oxidation experiment and the cyclic oxidation experiment at 650 and 700 C. A variety of modern analysis tests, such as scanning electron microscope (SEM), X ray diffraction analysis (XRD), electron probe (EPMA) and synchronous radiation X ray fluorescence technology (XFR), etc. The effects of oxidation temperature, oxidation time and oxidation mode on the morphology of the oxide film of GH3535 alloy, the depth of oxidation layer and the distribution of elements in the oxide / matrix interface were investigated. The oxidation process was discussed and the mechanism of high temperature oxidation of GH3535 alloy was revealed. The experimental results showed that the GH3535 alloy was oxidized at 700 degrees for 2000 hours at constant temperature. After that, the result of weight gain is 1.642mg/cm2, and the kinetic curve of oxidation follows the cubic law. When it belongs to the complete oxidation grade.870 and 980 C, the oxidation film is cracking and exfoliating because of the increase of temperature. The weight increase is obvious, which is 0.73mg/cm2 and 2.00mg/cm2 respectively, which is evaluated by the antioxidant grade of the alloy, and 870 is completely antioxidation. At 980 C, the oxide film thickness of GH3535 alloy is 4-6 m after oxidation oxidation at.700 C for 2000h, and it has a distinct layered structure. The outer layer is mainly Ni O and Ni Fe2O4, and the inner layer is mixed oxides of Cr2O3, Mo O2 and Ni, and there is no obvious internal oxygenation, and the thickness of the oxide film is 1 after constant temperature oxidation at 870. About 0 mu m, the continuous degree of the oxide film becomes worse and the oxide film of the outer layer appears exfoliated after 100h oxidation, exposes the inner oxide film and produces the internal oxidation hole. The temperature is further improved, the volatile substance of Cr, Mo is easily formed and the oxidation resistance of the alloy decreases. At 650 and 700, the GH3535 alloy has been circulated by 1000 cycles, respectively. No weight loss occurred during the experiment. No apparent peeling or visible holes were found on the surface of the alloy. The kinetic curve of oxidation still basically followed the cubic law of.650 C and the oxide film with fine particles and no spinel structure was formed after the oxidation of the surface. The surface of the oxide was formed at 700 degrees centigrade. The above results show that the GH3535 alloy has good antioxidant properties at 650 and 700 C, and is expected to be used in the thorium base molten salt stack for a long time.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG132.3

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