李志平,宋鹏,张瑞谦,李青.Cr涂层Zr-4合金包壳的高温空气氧化/扩散行为[J].表面技术,2023,52(9):241-246, 264.
LI Zhi-ping,SONG Peng,ZHANG Rui-qian,LI Qing.High-temperature Air Oxidation/Diffusion Behavior of Cr-coated Zr-4 Alloy Cladding[J].Surface Technology,2023,52(9):241-246, 264 |
| Cr涂层Zr-4合金包壳的高温空气氧化/扩散行为 |
| High-temperature Air Oxidation/Diffusion Behavior of Cr-coated Zr-4 Alloy Cladding |
| 投稿时间：2022-08-04 修订日期：2023-01-17 |
| DOI：10.16490/j.cnki.issn.1001-3660.2023.09.020 |
| 中文关键词: 多弧离子镀 Cr涂层 Zr-4合金 抗氧化性 扩散 |
| 英文关键词:multi-arc ion plating Cr coating Zr-4 alloy oxidation resistance diffusion |
| 基金项目:云南省稀贵金属材料基因工程(202002AB080001) |
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| Author | Institution |
| LI Zhi-ping | Key Laboratory of Reactor Fuel and Materials, Nuclear Power Institute of China, Chengdu 610213, China |
| SONG Peng | Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China |
| ZHANG Rui-qian | Key Laboratory of Reactor Fuel and Materials, Nuclear Power Institute of China, Chengdu 610213, China |
| LI Qing | Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China |
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| 中文摘要: |
| 目的 在Zr合金包壳表面制备Cr涂层，以提高Zr合金包壳在事故环境下的抗高温氧化性能。方法 采用多弧离子镀技术在Zr-4合金包壳上制备约17 μm的Cr涂层，通过X射线衍射(XRD)、扫描电子显微镜(SEM)、能量色散光谱(EDS)和电子探针(EPMA)等方法，分析试样氧化前后的相组成、微观形貌和扩散行为，并评估试样在1 100、1 200、1 300 ℃空气环境中氧化后的高温氧化性能。结果 沉积态Cr涂层显微结构致密均匀，(110)面有很强的织构。Cr涂层在高温空气中氧化60 min后，保持了涂层结构完整性。氧化后的Cr涂层Zr合金系统均为多层结构，包括外部Cr2O3层、中间Cr涂层、内部Cr-Zr扩散层和Zr合金基体。在涂层/基体界面上形成了具有Laves相的金属间ZrCr2扩散层，ZrCr2层下方的区域出现了大量分散的沉淀相。在Cr-Zr中间层和Zr合金界面处的不对称原子扩散导致Kirkendall空位生成，空位的聚集和合并导致空穴的形核和生长。结论 Cr涂层表面形成了致密的Cr2O3层，提高了Zr-4合金的抗高温氧化性能。通过研究高温空气中Cr涂层Zr-4合金包壳材料的高温空气氧化/扩散行为，可为耐事故涂层的开发、制备和应用提供一定的理论指导和技术支持。 |
| 英文摘要: |
| After the Fukushima nuclear power plant accident in 2011, accident tolerant fuel (ATF) materials become the focus of international research to cope with loss of the coolant accidents (LOCA) and more severe accidents in the nuclear industry. Zr alloys are widely used as fuel cladding structural materials because of their low thermal neutron cross section coefficient, good oxidation resistance, good mechanical properties and high corrosion resistance. Protective coatings are an effective way to increase the emergency response time in an accident. Cr coatings are one of the most promising ATF coatings because of their excellent oxidation resistance, high-temperature stability, and good deformation compatibility with Zr alloys in high-temperature environment. Cr coating was prepared on the surface of Zr alloy cladding by multi-arc ion plating technology to improve the high-temperature oxidation resistance of Zr alloy fuel cladding under accident environment. The high-temperature oxidation performance of the samples was evaluated at 1 100, 1 200 and 1 300 ℃ in an air environment. The microstructure of as-deposited Cr coatings was dense and homogeneous, with a strong texture on the (110) planes. No microcracks or voids were found on the coating surface and cross section, and the Cr coating had a uniform thickness of about 17 μm. The Cr coatings maintained the structural integrity after oxidation in air at 1 100, 1 200 and 1 300 ℃ for 60 min. The oxidation products of all Cr coatings were identified as Cr2O3. The relative strength of Cr (110) peak decreased with the increase of oxidation temperature. However, the relative strength of Cr2O3 (110) peak increased. The oxidized Cr-coated Zr alloy system was multi-layer:external Cr2O3 layer, intermediate Cr coating, internal Cr-Zr diffusion layer, and Zr alloy substrate. No microvoids, cracks or spalling were found on the surface of the dense Cr2O3 layer, but mound oxide layer was formed on the specimen surface. Considering that the PBR of Cr2O3 was 2.07, the strong volume expansion during high-temperature exposure led to an increase in compressive stress of the coating. Then, a large difference in the thermal expansion coefficients of Cr2O3 (9.6×10–6 /K) and Cr (6.5×10–6 /K) led to the formation of cracks or voids at the interface between the Cr coating and the Cr2O3 layer during cooling. Due to the inhomogeneous diffusion rate, the Cr/ZrCr2/Zr-4 interface became significantly rough. An intermetallic ZrCr2 diffusion layer with Laves phase was formed at the coating/substrate interface, and a large number of dispersed precipitates appeared in the region below the ZrCr2 layer. The solid-state reaction between Cr and Zr diffusion at high temperature led to the formation of the ZrCr2 diffusion layer. The asymmetric atomic diffusion at the interface between the Cr-Zr interlayer and the Zr alloy led to the formation of Kirkendall vacancies, and the aggregation and coalescence of vacancies led to the nucleation and growth of voids. A dense Cr2O3 layer on the surface of the Cr coating improves the high-temperature oxidation resistance of the Zr-4 alloy. The study on the oxidation/diffusion behavior of Cr coated Zr-4 alloy cladding materials in high-temperature air can provide theoretical guidance and technical support for the development, preparation and application of accident tolerant coatings. |
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