激光熔凝处理对Zr-1Nb核燃料包壳组织和性能的影响

Effect of Laser Melting Treatment on Microstructure and Properties of Zr-1Nb Nuclear Fuel Cladding

为了提高核燃料包壳Zr-1Nb合金的抗高温腐蚀性能,采用激光熔凝+真空退火热处理工艺对其进行表面处理。借助扫描电子显微镜(SEM)、X射线衍射(XRD)、拉曼等检测手段对锆管组织、成分及物相结构进行分析,使用探针式表面轮廓仪、显微硬度计和高压反应釜等仪器表征锆合金的粗糙度、硬度和耐蚀性。结果表明:经激光熔凝处理的锆管表面平整度提高;激光熔凝层物相主要由α-Zr和少量的m-ZrO2组成,且后续真空退火热处理没有改变锆合金的相组成;较高功率条件下进行激光熔凝显著降低锆管的高温耐蚀性能,而在较低功率进行激光熔凝工艺且辅助后续热处理的条件下,可以显著提高锆管的高温耐蚀性能;经激光熔凝处理后锆合金的显微硬度升高50~80HV0.1,热处理后硬度相应减小,但仍高于原始样品。

The Zr-1 Nb alloy was treated by laser melting and vacuum annealing in order to improve the high temperature corrosion resistance.The morphology of the melting layer was observed by scanning electron microscopy,phase compositions and quantities were determined by X-ray diffraction and Raman;surface roughness was determined by profile meter;and hardness was measured by the microhardness tester.In order to characterize the corrosion resistance,autoclave experiments were conducted for 70 days in an aqueous steam condition of 360℃ under 18.6 MPa in 0.01 mol/L LiOH solutions.The results show that the surface roughness of Zr-1 Nb cladding tubes is improved by laser melting;the laser melted layer is mainly composed ofα-Zr phase and a small amount of m-ZrO2,and the phase composition of laser melted layer does not change after heat-treatment;under high power condition,laser melting can reduce the high temperature corrosion resistance of Zr-1 Nb alloy.However,the high temperature corrosion resistance of Zr-1 Nb alloy can be improved significantly under the condition of low power laser melting and auxiliary heat treatment process.By laser melting treatment,microhardness of zirconium alloy can be increased by 50-80 HV0.1.And after heat treatment,microhardness of zirconium alloy is decreased compared with the laser melted sample,but it is still higher than the origin sample.