| Hot-dip coating can effectively improve the corrosion resistance of steel materials.It is the most widely used and basic technology in the corrosion resistance of steel products in the world.It not only has good protection effect,but also has low cost.However,under the conditions of hot-dip aluminum plating and hot-dip galvanizing,molten aluminum and zinc aluminum will seriously corrode the sink roll,stabilizing roll and other equipment,so as to shorten the service life of the equipment.Frequent replacement of sink roll and other equipment will not only reduce the production efficiency,but also directly affect the product quality,which is one of the most difficult problems in hot-dip galvanizing process.In response to this problem,this topic used 15#low carbon steel as the matrix,and used plasma spraying technology to prepare the surface separately Al2O3/Ni Co Cr Al Y,Zr O2/Ni Co Cr Al Y and Ni Cr-Cr3C2 coatings were used to analyze the corrosion resistance of Ni Cr-Cr3C2 and Zr O2/Ni Co Cr Al Y coatings to molten aluminum,Zr O2/Ni Co Cr Al Y and Al2O3/Ni Co Cr Al Y,used scanning electron microscope and energy spectrometer.Image-J image processing software calculated the porosity of the coating,and detected the hardness,bonding strength and thermal shock properties of the coating.The experimental results showed that the failure mechanism of the Ni Cr-Cr3C2 coating was that the zinc liquid reacted with the binder phase Ni in the coating to produce low melting point Ni Zn8,and the penetration of the aluminum liquid and the formation of Fe-Al compounds worked together to cause the coating to fall off and fail.Its service life was generally about 12 days.Al2O3/Ni Co Cr Al Y,Zr O2/Ni Co Cr Al Y coatings failed in molten aluminum and zinc-aluminum were mainly dued to the brittleness of ceramic materials,and although the addition of a transition layer could alleviate the thermal expansion difference between the working layer and the substrate to a certain extent.However,the thermal expansion difference between the transition layer and the substrate and the working layer was still large.Under the action of thermal stress,cracks would grow along the edge of the hole at the bonding interface and inside the coating,and the corrosive liquid would enter the coating along the crack Continuously peeling off the coating,resulted in the final fall off and failure of the coating.Among them,the Al2O3/Ni Co Cr Al Y coating failed after 12 days in the molten aluminum,and the service life of the Zr O2/Ni Co Cr Al Y coating in the molten aluminum and zinc-aluminum could reach more than 16 days.The porosity of Ni Cr-Cr3C2,Zr O2 and Al2O3coatings were 16.07%,3.03%and 2.41%respectively;the bonding strength between the three coatings and the substrate exceeded 80MPa,and the bonding strength between Al2O3 and Zr O2and the substrate was better,Ni Cr-Cr3C2 coating was slightly worse;the microhardness in descending order was Zr O2,Al2O3,and Ni Cr-Cr3C2;the thermal shock performance of Zr O2coating was worse than that of Ni Cr-Cr3C2 coating and Al2O3 coating at 580?and 680?.Based on the experiments done,it was concluded that the Zr O2/Ni Co Cr Al Y coating effect was better under the conditions of hot-dip aluminum and hot-dip galvanized aluminum,and the service life could reach more than 16 days.It could be used as the coating for sunken rolls in the two processes. |
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