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

Abstract

The Zr-1Nb 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 micro-hardness tester. In order to characterize the corrosion resistance,autoclave experiments were conducted for 70 days in an aqueous steam condition of 360℃ under 18.6MPa in 0.01mol/L LiOH solutions. The results show that the surface roughness of Zr-1Nb cladding tubes is improved by laser melting; the laser melted layer is mainly composed of α-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-1Nb alloy. However,the high temperature corrosion resistance of Zr-1Nb 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 50-80HV0.1. 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.

Keywords

• laser melting
• vacuum annealing heat-treatment
• Zr-1Nb alloy
• high temperature corrosion resistance