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MECHANISM OF THE RARE EARTH EFFECT IN HIGH TEMPERATURE OXIDE SCALES FORMED ON HEAT-RESISTING ALLOYS

耐热合金高温氧化皮中稀土效应的机理

基本信息

批准号：
62430014
负责人：
SAITO Yasutoshi
金额：
$ 18.56万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (A)
财政年份：
1987
资助国家：
日本
起止时间：
1987 至 1989
项目状态：
已结题

项目摘要

In this research, high temperature corrosion of heat-resisting alloys was studied with an emphasis on the effect of rare earth elements.Alloying additions of Y, Ce, La, Er, and superficial application of Y_2O_3, La_2O_3 and CeO_2 to Ni-20Cr-lSi alloys were found to decrease the mass gain of the alloy and increase Cr_2O_3 scale adherence during isothermal and cyclic oxidation, respectively. A mechanistic model based on the high oxygen diffusivities of the rare earth-oxides, was proposed to explain the effect of these additions on the growth mechanism and adherence of Cr_2O_3. A similar improvement in scale adherence was found in the case of Ni-20Cr-3Al alloys on which thin CeO_2 layers were deposited by vacuum evaporation. This superficial layer was observed to change the growth mechanism of the Cr_2O_3 scale and promote internal oxidation of aluminum.High temperature corrosion of heat-resisting alloys such as SUS 310 and SUS 430 were studied in sulfur, bromine and water vapor-containing environments. In sulfur and bromine-containing gases, formation of a thick, compact oxide scale was found necessary to prevent extensive corrosion of the alloy by forming sulfates or gaseous bromides at the scale/alloy interface. A high concentration of water vapor in the environment was observed to increase the isothermal oxidation rate of SUS 430 at temperatures around 900 K.

本研究主要研究了耐热合金的高温腐蚀，重点研究了稀土元素的影响。发现在Ni-20Cr-lSi合金中添加Y、Ce、La、Er合金化以及Y_2O_3、La_2O_3和CeO_2表面应用可降低合金的质量增益，并增加等温和循环过程中Cr_2O_3氧化皮的附着力。氧化，分别。提出了一种基于稀土氧化物的高氧扩散率的机理模型来解释这些添加物对Cr_2O_3的生长机制和粘附的影响。在 Ni-20Cr-3Al 合金上通过真空蒸发沉积了薄 CeO_2 层的情况下，也发现了氧化皮附着力的类似改进。观察到该表面层改变了Cr_2O_3氧化皮的生长机制，促进了铝的内部氧化。研究了SUS 310和SUS 430等耐热合金在含硫、溴和水蒸气的环境中的高温腐蚀。在含硫和含溴的气体中，发现有必要形成厚而致密的氧化皮，以通过在氧化皮/合金界面处形成硫酸盐或气态溴化物来防止合金的广泛腐蚀。据观察，环境中的高浓度水蒸气会增加 SUS 430 在 900 K 左右温度下的等温氧化速率。