热喷涂制备Cr涂层提高锆合金包壳耐事故性的研究

Study on Improving Accident Resistance of Zirconium Alloy Cladding by Thermal Spraying Cr Coating

采用热喷涂工艺大气等离子喷涂(APS)在Zr-4包壳管上成功制备了Cr涂层,目的是为核反应堆燃料组件两端焊接区域进行涂层的喷涂修复,以及完成焊接区的涂层包覆并与PVD涂层区域无缝连接,实现外表面抗氧化耐磨涂层全包覆.将Cr涂层在高达1200℃事故高温蒸汽和空气环境中氧化,采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、X射线能谱(EDS)和电子探针(EPMA)等多种分析技术,对其氧化前后进行了显微组织定性和定量分析.结果表明:Cr粉和喷涂态Cr涂层均为BCC相,喷涂态Cr涂层为典型的层状结构,涂层与基体的界面为机械咬合界面;在空气和流动蒸汽中进行高达1200℃的高温暴露后,均在Cr涂层表面形成致密的Cr_(2)O_(3)层,以及Zr-4基体与Cr涂层之间的相互扩散形成的Cr-Zr层;在高温水蒸气氧化后的Cr涂层试样,在其致密的氧化层上有高密度的针状和叶片形貌的晶须氧化物,但是在空气中未发现晶须状Cr_(2)O_(3).氧化试验表明,Cr涂层能有效提高Zr-4包壳管在高温空气和水蒸气中的抗氧化性.

The Cr coating was successfully prepared on the Zr-4 cladding tube by the thermal spraying process APS. The purpose is to spray and repair the welding area of the nuclear reactor fuel components at both ends,and to complete coating the welding area and seamlessly connect with the PVD coating area,so as to achieve fully coated protective coating of the outer surface with anti-oxidation and wear-resistant. The microstructure of Cr coating before and after oxidation was qualitatively and quantitatively analyzed by scanning electron microscope(SEM),X-ray diffractometer(XRD),X-ray energy spectrum(EDS) and electron probe(EPMA). Both Cr powder and sprayed Cr coating are BCC phase,sprayed Cr coating is a typical layered structure,and the interface between coating and substrate is mechanical occlusal interface.When exposed to high temperature up to 1200 ℃ in air and flowing steam,a dense Cr_(2)O_(3) layer was formed on the surface of Cr coating,and a Cr-Zr layer was formed by mutual diffusion between Zr-4 substrate and Cr coating. After high-temperature steam oxidation,the Cr coating samples had a high density of needle-like and leaf-shaped whisker oxides on the dense oxide layer,but no whisker Cr_(2)O_(3) was found in the air. The oxidation tests show that Cr coating can effectively improve the oxidation resistance of Zr-4 cladding tube in high-temperature air and flowing steam.