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首页> 外文期刊>Materials at High Temperatures >Burn-off of filamentous carbon and subsequent re-deposition on a 20Cr25Ni austenitic steel
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Burn-off of filamentous carbon and subsequent re-deposition on a 20Cr25Ni austenitic steel

机译：烧掉丝状碳并随后在20Cr25Ni奥氏体钢上重新沉积

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摘要

Filamentary carbon deposits can form on a 20Cr/25Ni (mass percent ) steel in a gas of high carbon activity even when the oxygen potential is sufficiently high to oxidise (of the main alloy constituents) both chromium and iron. These filaments are catalysed by metallic nickel which remains unoxidised but exists as small 10 nm particles within the porous oxide layer formed in the early stages of oxidation. The objective of the present work was to examine the re-deposition process when the initial deposit has been burned off. As in the previous work, carbon deposits were produced by exposure of specimens at 550 deg C to a gas mixture of CO_2/1 percent CO/1000vppmC_2H_4 at 1-atmosphere total pressure. Specimen examination was performed in a FEGSEM in sufficient detail that the specimen area could be relocated in subsequent examinations. Burn-off exposures were performed at 450 deg C in Ar/20 percent O_2. It was found that after 51 minutes burn-off exposure, considerable loss of carbon had occurred but that re-deposition occurred during subsequent exposure to the high-carbon environment. In contrast, a 2-hour burn-off exposure resulted in no further significant formation of carbon filaments during subsequent exposures. This effect of catalyst deactivation is related to the oxide formed during the burn-off stage.
机译：即使氧势足够高到足以氧化（主要合金成分的）铬和铁，即使在高碳活度的气体中，也可以在20Cr / 25Ni（质量百分比）钢上形成丝状碳沉积物。这些细丝由保持未被氧化的金属镍催化，但在氧化的早期阶段形成的多孔氧化物层中以10 nm的小颗粒存在。当前工作的目的是检查初始沉积物被烧掉时的重新沉积过程。与以前的工作一样，在1个大气压下，通过将样品在550℃下暴露于CO_2 / 1％CO / 1000vppmC_2H_4的气体混合物中来产生碳沉积物。在FEGSEM中对样品进行了足够详细的检查，以便可以在随后的检查中重新放置样品区域。燃尽曝光是在450°C的Ar / 20％O_2中进行的。发现在燃烧51分钟后，发生了相当多的碳损失，但是在随后的高碳环境暴露期间发生了再沉积。相比之下，2小时的燃尽暴露导致在随后的暴露过程中碳丝的形成不再明显。催化剂失活的这种效果与在燃烧阶段形成的氧化物有关。

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