Cr离子变价对镍基合金氟盐腐蚀行为的影响及机理研究

项目名称： Cr离子变价对镍基合金氟盐腐蚀行为的影响及机理研究

项目编号： No.51501217

项目类型： 青年科学基金项目

立项/批准年度： 2016

项目学科： 一般工业技术

项目作者： 侯娟

作者单位： 中国科学院上海应用物理研究所

项目金额： 20万元

中文摘要： 氟化物熔盐中镍基合金的腐蚀过程主要是Cr元素的选择溶解过程。Cr离子在腐蚀过程中发生歧化反应导致的变价行为，是腐蚀的主要驱动力。影响氟盐腐蚀的因素，本质上是对歧化反应和Cr离子变价产生影响。异质材料作用已被公认为是另一个影响熔盐腐蚀的重要因素，目前还存在研究不系统和认识不统一等问题。本项目以异质材料作用对镍基合金氟盐腐蚀的影响为研究对象，设计同质合金、异质材料绝缘和异质材料电接触三种典型试验装置。通过对镍基合金在三种装置中的腐蚀对比，不仅能够获得全面系统的异质材料作用与氟盐腐蚀行为之间的定量关系，更为研究Cr离子变价行为提供了典型的熔盐样本。引入了同步辐射研究方法，实现对腐蚀后固态和液态熔盐中Cr离子含量和变价趋势的测量，揭示异质材料体系中Cr离子变价行为影响氟盐腐蚀的机理。本研究不仅对统一异质材料作用影响熔盐腐蚀的理论认识，更为完善氟化物熔盐腐蚀研究提供重要的有益补充。

中文关键词： 熔盐腐蚀；高温腐蚀；活性元素；同步辐射；镍基合金

英文摘要： In high-temperature fluoride molten salt, the corrosion process of Ni-base alloy is mainly controlled by the selective dissolution of the active elements such as Cr. At the first step of corrosion, Cr diffuses into the metal/salt interface from metal matrix. Then it dissolves into the molten salt as Cr2+ ion. The valence change of Cr ion is induced in the next step by disproportionation reaction between Cr2+ and Cr3+. This process of valence change is considered as the key driving force for molten salt corrosion. Previous investigations had reported that the molten salt corrosion was accelerated by the interactions between alloys and other inert materials. However, studies on the influence of dissimilar materials interaction on molten salt corrosion has showed discrepancy. While a few mechanisms, including non-electric transfer, electrochemical reaction and mass transfer were proposed, no systematical and consistent understanding in the corrosion mechanism has been attained. Further, more efforts should be paid on the systematic and comprehensive research on the corrosion in fluoride molten salt under interactions between dissimilar materials. This proposal will investigate the corrosion behavior of GH3535 Alloy in FLiNaK molten salt, with focuses on the effects of Cr ion valence change induced by dissimilar materials interaction on corrosion. In the GH3535-graphite dissimilar material system, three setups will be designed and used for corrosion study. They are the GH3535-GH3535 same material setup, GH3535-graphite insulation setup, and the GH3535-graphite conduction setup. The corrosion evolution with time was compared in the three setups. The relationship between corrosion performance and dissimilar materials interaction will be obtained. In-situ molten salt corrosion instrument using synchrotron X-ray will be used for valence and content measurement of Cr ions. The synchrotron X-ray with high intensity and low damage was suitable for Cr2+ and Cr3+ measurement. The ion content measurement could achieve an accuracy of several ppm by synchrotron X-ray detection. The Cr ion valence and content measurement will clarify the mechanism of dissimilar material interaction influencing fluoride corrosion by affecting the Cr ion valence change. This study will improve and unify the theoretical understanding about the effect of dissimilar material interaction on fluoride corrosion. It also helps to supplement and the research scope of fluoride molten salt corrosion.

英文关键词： Molten salt corrosion ;High-temperature corrosion ;Active element ;Synchrotron radiation ;Ni-base alloy