New insights into internal oxidation of alloy 690 and model alloys in hydrogenated steam

IF 1.1 4区材料科学 Q4 MATERIALS SCIENCE, MULTIDISCIPLINARY

Corrosion Pub Date : 2023-10-30 DOI:10.5006/4439

Ali Riahi, Hao Zhu, Ali Eskandari, Suraj Y. Persaud, Roger C. Newman

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引用次数: 0

Abstract

ABSTRACT The oxidation behavior of Alloy 690 and Ni-xCr-10Fe model alloys exposed to 480 °C hydrogenated steam, in the nickel metal stability region, was studied using a variety of techniques, including time-resolved Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), and Electron Energy Loss Spectroscopy (EELS). The alloy underwent internal oxidation intragranularly, resulting in the expulsion of metallic Ni nodules to the surface. A compact Cr-rich “healing” layer developed over time at the intragranular internal oxidation front near grain boundaries and significantly retards further internal oxidation. Protective external Cr-rich oxide formed at and very near the grain boundaries, hindering intergranular oxidation. In view of the fact that the protective oxide forms micrometres away from the grain boundaries, one cannot simply say that Cr diffuses up the boundary and forms an oxide which spreads laterally – internal stress relief must play a role, just as it does within the grains, only with different mechanisms at play.

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690合金和模型合金氢化蒸汽内部氧化的新认识

采用时间分辨扫描电子显微镜(SEM)、透射电子显微镜(TEM)、飞行时间二次离子质谱(ToF-SIMS)和电子能量损失谱(EELS)等多种技术研究了690合金和Ni-xCr-10Fe模型合金在480℃氢化蒸汽下镍金属稳定区的氧化行为。合金在晶内发生内部氧化，导致金属镍结核向表面析出。随着时间的推移，在晶界附近的晶内氧化前线形成致密的富铬“愈合”层，并显著延缓进一步的内部氧化。保护性的外部富铬氧化物在晶界附近形成，阻碍了晶间氧化。鉴于保护性氧化物在离晶界几微米远的地方形成，我们不能简单地说Cr沿着晶界扩散并形成横向扩散的氧化物——内应力的消除一定起了作用，就像它在晶粒内部一样，只是机制不同而已。

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来源期刊

Corrosion MATERIALS SCIENCE, MULTIDISCIPLINARY-METALLURGY & METALLURGICAL ENGINEERING

CiteScore

2.80

自引率

12.50%

发文量

审稿时长

3 months

期刊介绍： CORROSION is the premier research journal featuring peer-reviewed technical articles from the world’s top researchers and provides a permanent record of progress in the science and technology of corrosion prevention and control. The scope of the journal includes the latest developments in areas of corrosion metallurgy, mechanisms, predictors, cracking (sulfide stress, stress corrosion, hydrogen-induced), passivation, and CO2 corrosion. 70+ years and over 7,100 peer-reviewed articles with advances in corrosion science and engineering have been published in CORROSION. The journal publishes seven article types – original articles, invited critical reviews, technical notes, corrosion communications fast-tracked for rapid publication, special research topic issues, research letters of yearly annual conference student poster sessions, and scientific investigations of field corrosion processes. CORROSION, the Journal of Science and Engineering, serves as an important communication platform for academics, researchers, technical libraries, and universities. Articles considered for CORROSION should have significant permanent value and should accomplish at least one of the following objectives: • Contribute awareness of corrosion phenomena, • Advance understanding of fundamental process, and/or • Further the knowledge of techniques and practices used to reduce corrosion.