| Zirconium and its alloys is developed a kind of important metal in the 1930 s,due to its excellent physical and chemical properties are widely used in petrochemical industry,medical apparatus and instruments,the nuclear industry system,and other fields,especially the development and application of zirconium alloy is used in the nuclear,created the huge economic and social benefits,but,in a nuclear reactor under the environment of high temperature,zirconium easily happened oxidation reaction,thus reducing its good performance,the metal surface modification technology is considered to be an effective and economy of improving the performance of the metal surface,the surface modification of zirconium and its alloy,at the same time of increase its oxidation resistance,It is very important to ensure the excellent performance of zirconium alloy.The preparation of protective coating on the surface of zirconium alloy by physical vapor deposition technology can effectively improve the wear resistance and corrosion resistance of the alloy matrix and improve its accident resistance.However,the coating prepared by this method has poor bonding strength with the zirconium alloy,and is mechanically bonded.Under long-term working conditions,the coating is easy to peel off,thus losing the protective effect of the substrate.The laser micro-melting technology can realize the metallurgical bonding between the coating and the substrate and enhance the bonding strength between the coating and the substrate.However,after laser micro-melting of thecoating,the coating surface will crack due to many factors,such as the brittle coating material,the difference in the linear expansion coefficient between the coating and the substrate,and the thermal stress caused by the rapid laser heating and cooling speed.Based on zirconium alloy substrate by magnetron sputtering technology NiCr composite coating was prepared on the surface,and by using the fiber laser coating for laser micro welding processing,studied under different process parameters(thickness,the density of laser power,scanning speed and preheating temperature,etc.),laser micro welding processing of NiCr composite coating cracking behavior,the influence of and the preparation of the magnetron sputtering NiCr composite coating as a comparative object,explore the micro laser melting treatment on NiCr the influence of the structure and performance of the composite coating characteristics(such as oxidation resistance,microhardness,bonding strength,etc.).The results show that the NiCr composite coating treated by laser micro-melting can effectively improve the shadow benefit of the coating in the process of magnetron sputtering deposition coating,reduce the defects of the coating such as holes,and the bonding between the coating and the substrate is changed from the original mechanical bonding to the metallurgical bonding,which significantly improves the bonding strength of the coating and the substrate.Coating cracking caused by residual stress release during laser micro-melting NiCr composite coating can be alleviated by optimizing process parameters.(as in the NiCr preset thickness of 30 mu to 60 w/m,the laser power density was,scanning speed is 1200 mm/s,overlapping rate is 30% and the preheating temperature of 300 ?),and the process parameters,the coating porosity is lower than without micro melt treatment of magnetron sputtering,NiCrcoating film base bonding strength and microhardness performance is also better than those without micro melt treatment such as coating. |
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