引用本文:张腾飞,廖海燕,阮海波,苏永要,王锦标,徐照英,董井忍.锆合金表面Mo/Al/Cr复合涂层的抗高温水蒸气氧化性能[J].中国表面工程,2023,36(2):97~103
ZHANG Tengfei,LIAO Haiyan,RUAN Haibo,SU Yongyao,WANG Jinbiao,XU Zhaoying,DONG Jingren.High Temperature Steam Oxidation Resistance of Mo / Al / Cr Composite Coating on Zirconium Alloy[J].China Surface Engineering,2023,36(2):97~103
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锆合金表面Mo/Al/Cr复合涂层的抗高温水蒸气氧化性能
张腾飞1, 廖海燕2, 阮海波1, 苏永要3, 王锦标1, 徐照英1, 董井忍1
1.重庆文理学院材料科学与工程学院 重庆 402160;2.昆明理工大学材料科学与工程学院 昆明 650093;3.重庆大学材料科学与工程学院 重庆 401331
摘要:
锆合金是重要的核燃料包壳材料,在包壳表面沉积抗高温水蒸气氧化涂层是在失水事故中避免核泄漏的有效途径,然而涂层在高温氧化过程中存在氧化产物不稳定及界面扩散问题。用磁控溅射的方法在 Zr-4 合金表面沉积 Mo / Al / Cr 复合涂层,拟利用 Al 层生成氧化铝提升抗氧化温度上限,利用 Mo 层阻挡 Al 与 Zr-4 基体的扩散。用 SEM 表征涂层的表面及横截面形貌,利用 XRD 分析涂层物相结构,用纳米压痕的方法评价涂层的力学性能,用管式炉连接水蒸气发生器来评价涂层的抗高温水蒸气氧化性能。结果表明:在锆合金表面制备的 Mo / Al / Cr 复合涂层与基体结合良好,结构完整,界面清晰,硬度高于 Zr-4 合金基体。在高温水蒸气氧化试验中,复合涂层中的 Al 会发生熔融,导致涂层结构的破坏而不能生成连续致密氧化铝膜。在 Cr 层、Al 层失效的情况下,Mo 层可以有效阻挡 Al 及 O 元素向基体内部扩散。探讨了 Al 作为抗氧化层及 Mo 作为扩散阻挡层的可行性,试验结果可为核燃料包壳涂层的设计选材提供借鉴和支撑。
关键词:  磁控溅射  Mo / Al / Cr 涂层  显微结构  高温水蒸气氧化
DOI:10.11933/j.issn.1007?9289.20220222001
分类号:TG156;TB114.
基金项目:国家自然科学基金(U20A20232)、重庆市教委科研(KJQN202101316,KJQN201901340,KJQN202101303)和重庆市科技局(cstc2021ycjhbgzxm0176,cstc2018jcyj-yszxX0003)资助项目
High Temperature Steam Oxidation Resistance of Mo / Al / Cr Composite Coating on Zirconium Alloy
ZHANG Tengfei1, LIAO Haiyan2, RUAN Haibo1, SU Yongyao3, WANG Jinbiao1, XU Zhaoying1, DONG Jingren1
1.College of Materials Science and Engineering, Chongqing University of Arts and Sciences,Chongqing 402160 , China;2.College of Materials Science and Engineering, Kunming University of Science and Technology,Kunming 650093 , China;3.College of Materials Science and Engineering, Chongqing University, Chongqing 401331 , China
Abstract:
Zirconium alloys are important materials for nuclear fuel claddings. When a loss of coolant accident (LOCA) occurs, the zirconium alloy cladding will be oxidized by the high-temperature (>1 000 ℃) steam, generating hydrogen and releasing significant heat. If the emergency action is not taken promptly, a hydrogen explosion or nuclear leakage will occur. The deposition of coatings with high temperature steam oxidation resistance, such as Mn+1AXn phase, FeCrAl, and Cr coatings, on the cladding surfaces is an effective mechanism for delaying the hydrogen explosion and nuclear leakage of a LOCA. Of all the coatings, the Cr coating is considered the most promising for practical application because of its good oxidation resistance in high-temperature steam and excellent corrosion resistance in subcritical water. However, the oxidation products of Cr coatings are unstable, and the Cr-Zr eutectic reaction will occur at the interface during the process of high-temperature oxidation, which limits the performance of the Cr coatings. In this paper, a Mo / Al / Cr composite coating is deposited on the surface of a Zr-4 alloy by the magnetron sputtering method. The outer Cr layer is designed to resist the corrosion of the subcritical water under normal conditions. The Al layer is proposed to improve the upper limit of the oxidation resistance of the composite coating during accident conditions because aluminum oxide is more stable than chromium oxide at high temperatures. The Mo layer is designed to inhibit the diffusion between the Al layer and the Zr-4 substrate. Cr coatings and Al / Cr coatings are also prepared on the surfaces of the Zr-4 alloys as reference samples. The surface and cross-sectional morphologies of the coatings are characterized by scanning electron microscopy; the phase structures of the coatings are analyzed by X-ray diffraction; the mechanical properties of the coatings are evaluated by the method of nano-indentation; and the high temperature steam oxidation resistance of the coatings is evaluated using a tube furnace connected to a steam generator. The results show that the Cr, Al / Cr, and Mo / Al / Cr coatings deposited on the Zr-4 alloys have good adhesion to the Zr-4 substrates, which exhibit clear interfaces and pure phase structures. Because the preparation process for the outer Cr layer is the same, the surface hardness and modulus of the Cr, Al / Cr and Mo / Al / Cr coatings are similar and higher than those of the Zr-4 alloy. After the high-temperature steam oxidation, the Cr, Al / Cr and Mo / Al / Cr coatings display surfaces with cracks, which may result from the difference in the thermal coefficients of expansion of the Cr2O3 and residual Cr layers. The cracks provide pathways for the oxidizing medium, which induces the oxidation of the substrate or the inner layer of the composite coatings. The Al layer in the Al / Cr and Mo / Al / Cr composite coatings melts, resulting in the destruction of the coating structure; thus, it is unable to form a continuous dense alumina film. For the Al / Cr coating, when the Cr and Al layers fail, the oxygen will diffuse to the Zr-4 substrate, forming zirconium oxide. For the Mo / Al / Cr coating, even though the Cr layer fractures and the Al layer melts at high temperatures, the residual Mo layer can effectively restrict the diffusion of the Al and O elements into the Zr-4 substrate. This paper explores the feasibility of using the Al layer as an oxidation resistant layer and the Mo layer as a diffusion barrier layer. We have demonstrated that the layers with a low melting point, such as the Al layer, are not suitable for the composite coatings applied for high-temperature conditions and that the Mo layer is an effective diffusion barrier at a temperature of 1000 ℃. The results of this paper provide reference and data support for the material design of nuclear cladding coatings.
Key words:  magnetron sputtering  Mo / Al / Cr coating  microstructure  high temperature steam oxidation
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