Preparation And Characterization Of (Zr_50.7Cu₂₈Ni₉Al_12.3)₉₈Y₂ Corrosion Resistant Amorphous Coatings For High Activity Metal Protection

High-active metal materials（HAMMs）represented by actinides have important applications in national defense.Corrosion is the most common failure form of the HAMMs.Therefore,it is of great significance to develop coatings with high corrosion resistance for the protection of the HAMMs.Metallic glasses（MGs）have unique structure and exhibit excellent corrosion resistance.By using laser cladding technology,non-defect MG based coatings with good metallurgical bonding can be prepared on the surface of HAMM,and the effective protection of HAMMs can be realized.Zr-Cu-Ni-Al MGs have attracted much attention due to their strong glass forming ability（GFA）,good corrosion resistance,and the absent of noble metals or highly toxic metals.However,they are easily crystallized by oxidation.The addition of Y element can preferentially form stable Y₂O₃ with the oxygen,and avoid the formation of oxides such as Zr₂O₃ and Al₂O₃.Therefore,in this study,Zr_50.7Cu₂₈Ni₉Al_12.3 was selected as the base alloy.The influence of the Y microalloying on the GFA and corrosion resistance of the Zr_50.7Cu₂₈Ni₉Al_12.3 MG were studied,and the composition optimization was carried out.The hydrogen resistance performance of the optimized MG was investagted,and Zr-Cu-Ni-Al-Y MG composite coatings were prepared by laser cladding on analog 45#steel substrate.The present study provides potential solutions for corrosion protection of the HAMMs.In this study,(Zr_50.7Cu₂₈Ni₉Al_12.3)_100-xY_x（x=0（Y0）,1（Y1）,2（Y2）,3（Y3））specimens were prepared by copper casting,and their thermodynamic and electrochemical corrosion properties were studied.It is found that appropriate addition of Y element can improve the GFA.Y2 alloy has the best comprehensive performance of GFA and thermal stability.Its（35）T is 105 K,and the T_rg,γandδparameters are 0.604,0.435 and 1.762,respectively.E_g,E_xand E_p were 220,290 and 288 k J/mol,respectively.The addition of Y element will reduce the corrosion resistance of the alloy to a certain extent.The corrosion resistance of Y2 alloy is the best among the developed Zr-Cu-Ni-Al-Y alloys.The self-corrosion current density of and the self-corrosion potential Y2 alloy are 1.1×10^-8 A/cm² and-0.42 V,and the interfacial charge transfer resistance of metal/corrosive liquid is the highest.In addition,Y2MG ribbon was prepared by spinning quenching,and the deuterium penetration and deuterium retention behavior were studied.It was found that hydrogen could hardly penetrate the Y2 MG ribbon with thickness of 70μm,indicating that the Y2 MG has excellent hydrogen permeation resistance.In this study,Y2 MG was selected to carry out atomization powder preparation research,and nearly spherical powders were prepared.The median particle diameter of the powder is22μm,and the the powder was mainly consisted by amorphous phasewith small amount of Zr O₂ precipitates.Single pass was laser cladded with the prepared powder.The influence of laser energy density on the morphology of the single pass was studied.It was found that the thickness of single pass increases with increasing laser energy density,and the surface quality of the single pass improves.However,when the laser energy density reaches 0.206W·min/mm,the height of the single pass stops increasing and the dilution effect of the substrate is greatly improved.Dense Y2 MG composite coating was successfully prepared under different laser energy densities after the lap rate optimization.The coating surface is smooth,and there are a few holes and cracks.The coating is mainly composed of amorphous phase and crystalline phase such as Zr O,Al Cu₂Zr,Y₂O₃,Cu Zr and Cu₂O.The amorphous phase content increases first and then decreases with the increasing laser energy density.The dilution of Fe in the substrate leads to severe crystallization in the middle and lower part of the coating,which makes the coating divided into the amorphous region on the surface and the crystallization region in the middle and bottom.With the increase of laser energy density,the proportion of surface amorphous region increases first and then decreases.When the laser energy density is 0.150 W·min/mm,the proportion of amorphous layer is the highest.In this paper,electrochemical tests were carried out on the prepared Y2 coatings in 1mol/L H₂SO₄ solution.It was found that the coatings exhibit wide passivation zones,and their corrosion resistance are much better than that of the 45#steel substrate.According to the passivation current density and impedance curve,it is found that the corrosion resistance of the coating is related to the amorphous phase content and the crack density.When the amorphous phase content differs greatly,better corrosion resistance will be obtained under higher amorphous phase content.When the amorphous phase content is close,worse corrosion resistance will be obtained with more surface cracks.When the laser energy density is 0.150 W·min/mm,the coating has the best corrosion resistance,and the passivation current density is 1.58×10^-4 A/cm².Pittings form on the surface of the coating are preferentially initiated near the cracks and other defects.The pittings are rich in Ni and Fe elements.Passive film is mainly composed of Zr O₂ and Al₂O₃.In order to further improve the corrosion resistance of the coating,multilayer amorphous composite coatings were laser cladded.It was found that with the increase of coating layers,the amorphous phase content on the coating surface decreases,but the defects such as cracks were effectively reduced.Multilayer coatings have wide passivation zone,and their corrosion resistance increases with the increasing layers,indicating that reducing the surface crack density can improve the corrosion resistance of the coating.In this study,(Zr_50.7Cu₂₈Ni₉Al_12.3)_100-xY_x（x=1,2,3）MGs were developed,and the GFA of the alloy was systematically evaluated.The hydrogen permeation resistance of the Y2MG was explored.The Y2 MG composite coatings were prepared by laser cladding,and the microstructure evolution and corrosion resistance of the coating were systematically studied.The corrosion resistance of the coatings is further improved by preparing multilayer coatings.The relevant research provides effective technical support for the preparation of protective coatings for HAMMs.