| With the development of modern industrial technology,nickel-based superalloys are widely used in aerospace,petrochemical,energy and other industrial fields.As a widely used precipitation-reinforced nickel-based superalloy,GH4169 has good high temperature oxidation resistance,corrosion resistance,radiation resistance and welding properties.But when its use temperature exceeds 1000?,the high temperature oxidation resistance of GH4169 will drop sharply,and covering a layer of thermal barrier coating on its surface is needed for industrial requirements.In this paper,six La2Zr2O7 ceramic powders with different ratios were pre-layered on the surface of the GH4169 substrate,La2Zr2O7 coatings with high temperature oxidation resistance at 1100?,thermal shock resistance at 25-1100?and corrosion resistance in3.5wt.%Na Cl solution were successfully prepared by laser cladding.Microstructure and phase composition,high temperature oxidation,thermal shock resistance and corrosion resistance of the coatings were investigated by XRD,SEM,weight gain method,water cooling method,electrochemical method and other technical means.The following conclusions are obtained:(1)La2Zr2O7 thermal barrier coatings were successfully prepared by laser cladding under six different ratios.(2)The oxidation weight gain rate of the six coatings after high temperature oxidation at1100?110h is less than that of the GH4169 substrate,The minimum oxidation weight gain of coating 2 is 15.7mg/cm2,which is about 2/3 of GH4169 substrate oxidation weight gain of 23.8mg/cm2.The oxidation of the coating sample follows the selective oxidation theory.(3)The number of cycles of the first crack occurrence of Coating 1 and Coating 2 after thermal shock at 25-1100?is higher than that of the GH4169 matrix,and the others are lower than the GH4169 matrix.The highest number of cycles for the first crack of coating1 is 71,which is about 1.18 times of that of GH4169 substrate.(4)The corrosion potential of the six coatings in 3.5wt.%Na Cl solution were higher than those of the GH4169 substrate,and the corrosion current lower than those of the GH4169substrate,respectively.The highest self corrosion potential of coating 1 is-0.82508V,and the lowest corrosion current density is 9.6259×10-6A/cm2;The lowest self corrosion potential of the substrate is-1.13342V,and the highest corrosion current density is 1.6738×10-4A/cm2.La2Zr2O7 phase and Zr O2 phase are the main reasons for the improvement of corrosion resistance of the coating. |
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