| With the rapid development of Chinese nuclear power industry, nuclear reactor structural material becomes more and more important and it takes our attention gradually. Especially, zirconium alloys are important structural components and cladding materials, which are commonly used in nuclear reactors. In order to improve the corrosion property and service cycle of zirconium alloys in actual working conditions, the surface of the Zr-1Nb alloy was modified by laser melting plus heat treatment technology.Surface microstructure of zirconium alloy was characterized by optical microscope, scanning electron microscopy(SEM), Energy Dispersive X-Ray Spectroscopy(EDS) and X-ray diffraction(XRD). Probe type surface profiler and electrochemical workstation were performed to characterize surface roughness and corrosion resistance.According to experiment results of the Zr-1Nb alloy samples after CO2 laser melting process. Zirconium melting layer was composed of two layers of different organization and the surface microstructure was mainly of α-Zr and tiny amounts of ZrN0.28. Laser melting technology eliminated the surface texture of zirconium tube and improved the surface roughness which is beneficial to the surface forming quality. The grains of laser melting overlap region were coarse and prone to pitting that had a certain negative influence on the corrosion resistance of zirconium tube. The corrosion currents of electrochemical samples including P=300W, V=200mm/min and P=150W, V=400mm/min were an order of magnitude lower than the original zirconium tube, which could effectively improve the corrosion resistance of zirconium tube.Vacuum annealing treatment on zirconium laser melting samples improved the organizations of laser melting overlap region and further improved the surface roughness of zirconium tube. Annealing temperature chose 475 ℃ for 4 h.The surface microstructure was mainly of α-Zr and tiny amounts of m-ZrO2 and ZrN0.28. The corrosion currents of annealing treatment samples were lower than the original sample and lower than the corresponding laser melting samples. The electrochemical sample of P=150W, V=400mm/min, T=475℃ had the best corrosion resistance and the next were 20140403-2 sample( P=300W, V=200mm/min, T=475 ℃) and 20140403-8 samle(P=150W, V=500mm/min, T=475℃).All samples did’t have pitting. Annealing treatment could improve the corrosion resistance of zirconium tube. |
