本文選題：GH3535鎳基合金 + 氧化動力學(xué)　； 參考：《重慶交通大學(xué)》2015年碩士論文

【摘要】：鎳基高溫合金由于具有較高的高溫強度、良好的韌性、優(yōu)越的耐腐蝕和抗氧化能力,在化工、石油和核工業(yè)等領(lǐng)域得到了廣泛地應(yīng)用。在2011年啟動的中國科學(xué)院戰(zhàn)略性先導(dǎo)科技專項《未來先進核裂變能》中,已將Ni-Mo-Cr系合金選定為釷基熔鹽堆的關(guān)鍵結(jié)構(gòu)材料。GH3535合金為我國自主研制的專門用于釷基熔鹽堆的一種鎳基高溫合金,其化學(xué)成分與Hastelloy N合金非常接近�，F(xiàn)階段GH3535合金仍處于研制起步階段,其在高溫環(huán)境中的抗氧化性能優(yōu)劣,將直接影響熔鹽反應(yīng)堆的使用安全及運行壽命。本文選用GH3535合金為研究對象,開展了GH3535合金700-980℃溫度范圍的恒溫氧化實驗和650℃與700℃循環(huán)氧化實驗。采用掃描電鏡(SEM)、X射線衍射分析(XRD)、電子探針(EPMA)和同步輻射X射線熒光技術(shù)(XFR)等多種現(xiàn)代分析測試手段,研究了氧化溫度、氧化時間和氧化方式對GH3535合金氧化膜的形貌特征、氧化層深度、氧化物/基體界面元素分布的影響,探討了高溫氧化過程,揭示了GH3535合金的高溫氧化機理。實驗結(jié)果表明,GH3535合金在700℃經(jīng)過2000小時的恒溫氧化后,增重結(jié)果為1.642mg/cm2,氧化動力學(xué)曲線遵循立方規(guī)律,屬于完全抗氧化等級。870℃和980℃恒溫氧化時,由于溫度提高導(dǎo)致氧化膜出現(xiàn)開裂和剝落現(xiàn)象,增重明顯,分別為0.73mg/cm2和2.00mg/cm2,由合金抗氧化等級評定,870℃屬于完全抗氧化,而980℃則屬于抗氧化等級。700℃恒溫氧化2000h后GH3535合金的氧化膜厚度為4-6μm,且具有明顯的分層結(jié)構(gòu),外層主要是Ni O和Ni Fe2O4等復(fù)合氧化物,內(nèi)層則為Cr2O3、Mo O2和Ni Cr2O4等混合氧化物,無明顯內(nèi)氧化現(xiàn)象;870℃恒溫氧化100h后氧化膜厚度為10μm左右,氧化膜連續(xù)程度變差;980℃氧化100h后外層氧化膜出現(xiàn)剝落,露出內(nèi)層氧化膜,并伴有內(nèi)氧化孔洞產(chǎn)生。溫度進一步提高,Cr,Mo易形成揮發(fā)性物質(zhì)而導(dǎo)致合金的抗氧化性能下降。在650℃和700℃,分別對GH3535合金進行了1000次循環(huán)氧化實驗。實驗過程中沒有出現(xiàn)失重現(xiàn)象,合金表面也沒有出現(xiàn)明顯剝落或肉眼可觀察到的孔洞。氧化動力學(xué)曲線仍基本遵循立方規(guī)律。650℃循環(huán)氧化后表面氧化顆粒細小且沒有形成尖晶石結(jié)構(gòu)的氧化膜,700℃循環(huán)氧化時表面已形成了具有尖晶石結(jié)構(gòu)的致密氧化膜。以上結(jié)果表明GH3535合金在650℃和700℃具有良好的抗氧化性能,有望在釷基熔鹽堆中長期使用。
[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.
【學(xué)位授予單位】：重慶交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TG132.3

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本文編號：1962970