Al/Mo-C中间层对锆合金表面Zr2Al3C4涂层界面性能影响

锆合金表面涂层研究作为提高核燃料包壳事故容错能力的重要技术手段之一, 能够有效解决失水事故下锆水反应的问题。Zr₂Al₃C₄以其优异的抗氧化性能和适用于核环境的化学组分而成为锆合金包壳的候选涂层材料之一。由于Zr₂Al₃C₄涂层与锆合金基底之间的元素扩散以及热膨胀系数不匹配等问题, 在其上制备Zr₂Al₃C₄涂层的相关研究较少。本研究通过磁控溅射结合后续热处理工艺, 以Al/Mo-C作为扩散屏障层, 在锆合金基底上制备Zr₂Al₃C₄涂层。结合X射线衍射仪、扫描电子显微镜和透射电子显微镜等分析手段, 研究了Al/Mo-C中间层对涂层的相和微观结构的影响。结果表明, 在800 ℃退火3 h后, 未添加中间层的涂层开裂, 同时由于Zr-Al-C涂层与基底之间存在明显的元素扩散, 导致Zr₂Al₃C₄无法成相。Al/Mo-C中间层作为扩散屏障, 能够有效阻止退火过程中Zr-Al-C涂层和基底之间的元素扩散, 从而大大降低Zr-Al-C涂层与标准化学量比的偏差, 有利于最终涂层中Zr₂Al₃C₄相的形成。此外, 该扩散屏障层能够抑制Zr₂Al₃C₄涂层在退火过程中产生裂纹, 同时将退火态涂层与锆合金基底的结合力提高30 N。

Zr2Al3C4 Coatings on Zirconium-alloy Substrates with Enhanced Adhesion and Diffusion Barriers by Al/Mo-C Interlayers

Zircaloy coating is one of the crucial technical ways to improve the accident tolerance of nuclear fuel cladding, which enables the zirconium-water reaction problems to be solved. Zr₂Al₃C₄ coating is one type of candidate solutions to improve the high-temperature oxidation resistance of zirconium claddings. However, little study has been performed on the synthesis of Zr₂Al₃C₄ coatings on zirconium alloy substrates due to the inter-diffusion, as well as the difference of the thermal expansion coefficients between the Zr₂Al₃C₄ coating and the substrates. In this study, Zr₂Al₃C₄ coatings were prepared through room-temperature magnetron sputtering and post annealing on zirconium alloy (ZIRLO) substrates with magnetron-sputtered Al/Mo-C interlayers. The effects of Al/Mo-C interlayers on phases and microstructures of Zr-Al-C coatings after annealing were studied by different methods. It is found that the coatings without interlayer are broken and no Zr₂Al₃C₄ phase is formed due to significant interdiffusion between the Zr-Al-C coating and the substrate during annealing at 800 ℃ for 3 h. The Al/Mo-C interlayers prevented elemental diffusion between Zr-Al-C coatings and substrates during the post-annealing process. The Al/Mo-C interlayers act as diffusion barriers and greatly reduce the stoichiometric deviations from Zr₂Al₃C₄ phase, which facilitates the formation of the Zr₂Al₃C₄ phase in the final coating. Moreover, this diffusion-barrier layers contribute to eliminating cracks induced by the difference of the thermal expansion coefficients between the Zr₂Al₃C₄ coatings and substrates. At the same time, the adhesions between Zr-Al-C coatings with Al/Mo-C interlayers and substrates were improved after annealing, with their strength exceeding 30 N.