引用本文:陈思雨,张弦,李腾,刘静,吴开明.多元氯化物熔盐中表面改性Inconel625的腐蚀行为[J].中国表面工程,2024,37(1):87~99
CHEN Siyu,ZHANG Xian,LI Teng,LIU Jing,WU Kaiming.Corrosion Behavior of Surface Modified Alloy Inconel 625 in Chloride Molten Salts[J].China Surface Engineering,2024,37(1):87~99
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多元氯化物熔盐中表面改性Inconel625的腐蚀行为
陈思雨1, 张弦1, 李腾2, 刘静1, 吴开明1
1.武汉科技大学冶金工业过程系统科学湖北省重点实验室 武汉 430081;2.中国原子能科学研究院放射化学研究所 北京 102413
摘要:
氯化物熔盐作为传热蓄热介质,对太阳能热发电储能系统中金属部件产生严重腐蚀,而针对镍基合金在氯化物熔盐中的高温腐蚀行为研究较少。以镍基合金 Inconel 625 和经过表面改性后的 Inconel 625(ST In625)为研究对象,利用组织表征、 微拉伸试验及高温熔盐浸泡试验,研究不同样品的力学性能变化以及在二元和三元氯化物熔盐中的腐蚀行为。结果表明:ST In625 合金强度明显提升,拉伸塑性有所下降。腐蚀初期,两种样品在氯化物熔盐中形成的氧化膜以 Cr2O3和 NiCr2O4 为主, ST In625 表面产生的腐蚀坑较少;腐蚀后期,在两种样品表面均检测到 NiO,二元氯化物熔盐中两种样品表面未生成明显氧化层,出现明显腐蚀坑,而三元氯化物熔盐表面会生成新的 Cr2O3 和 NiCr2O4 絮状氧化层,无腐蚀坑出现。因此,在氯化物熔盐中 ST In625 的腐蚀失重较小,耐蚀性明显提高,且两种样品在二元氯化物熔盐中的腐蚀速率较低、但存在明显晶间腐蚀; 在三元氯化物熔盐中腐蚀速率更高,而晶间腐蚀较为轻微。通过表面改性提高了镍基合金在氯化物熔盐环境中的耐蚀性,可为太阳能热发电储热材料的金属部件选择提供全新的思路。
关键词:  镍基合金  氯化物熔盐  表面改性  微拉伸  高温腐蚀
DOI:10.11933/j.issn.1007-9289.20221121001
分类号:TG156;TB114
基金项目:
Corrosion Behavior of Surface Modified Alloy Inconel 625 in Chloride Molten Salts
CHEN Siyu1, ZHANG Xian1, LI Teng2, LIU Jing1, WU Kaiming1
1.Hubei Province Key Laboratory of Systems Science in Metallurgical Process,Wuhan University of Science and Technology, Wuhan 430081 , China;2.Institute of Radiochemistry, China Institute of Atomic Energy, Beijing 102413 , China
Abstract:
With the implementation of a global sustainable development strategy, further development of solar energy resources has been pushed to commanding heights. Presently, nitrate and carbonate are the main energy storage materials in solar tower power generation systems; however, the application temperature is generally lower than 700 ℃. The maximum temperature of chloride molten salt can reach 900 ℃ as a heat transfer and heat storage medium, but it causes serious corrosion to metal parts. As a nickel-based superalloy, Inconel 625 has the advantages of high-temperature resistance, corrosion resistance, oxidation resistance, and fatigue resistance. However, there are few studies on the high-temperature corrosion behavior of Inconel 625 in chloride molten salt. In this study, Inconel 625 and the surface modified Inconel 625 (ST In625) after surface mechanical grinding and annealing at 750 ℃ are evaluated. The microstructures and mechanical properties of the two alloys are characterized using backscattered electron diffraction (EBSD) and microtensile tests. The two alloys are immersed in molten binary and ternary chloride salts, and their static corrosion rates are analyzed using the weight loss method. Field emission electron microscopy (SEM / EDS), laser confocal micro-Raman spectrometry (Raman), and field emission electron probe analysis (EPMA) are used to characterize the surface and cross-sectional morphologies, analyze the composition of the corrosion products and evaluate the high-temperature corrosion mechanism of the two alloys in chloride molten salt. The results showed that the grain size of ST In625 obtained after mechanical grinding and annealing was smaller and more uniform than that of In625. Moreover, ST In625 has small-angle grain boundaries with a uniform distribution, and its alloy strength increases significantly, whereas its tensile plasticity decreases. At the initial corrosion stage, Cr2O3 and NiCr2O4 were the main oxide films formed in the molten chloride salt of the two samples, and the corrosion pits on the surface of ST In625 were fewer than those of In625, which was due to the lower corrosion sensitivity and better self-passivation performance of the nano-twin layer on the surface of ST In625. In the later stage of corrosion, NiO was detected on the surface of both samples. No obvious oxide layer was formed on the surface of the two alloys in the binary chloride molten salt, and obvious corrosion pits appeared, whereas new Cr2O3 and NiCr2O4 oxide layers were formed on the surfaces of the two alloys in the ternary chloride molten salt, and no corrosion pits appeared. Therefore, the corrosion loss of ST In625 in the chloride molten salt was small, and the corrosion resistance was significantly improved. The corrosion rates of the two alloys in the binary chloride molten salt were low; however, intergranular corrosion was evident. Moreover, the corrosion rate was high in the ternary chloride molten salt, and the intergranular corrosion was slight. This study improves the corrosion resistance of nickel-based alloys in chloride molten salt environments by surface modification and provides a new idea for the selection of metal components for solar thermal power storage materials. In the future, surface modification and heat treatment can improve the corrosion resistance of nickel-based alloys and other high-temperature-resistant metals in molten salt environments, which have the potential for industrial application. The service behavior of high-temperature-modified alloys in industrial environments is worthy of further investigation.
Key words:  nickel base alloy  chloride molten salt  surface modification  micro tensile  high temperature corrosion
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