| At present, non-ferrous metal aluminium processing industries consume large amount of energy. Liquid aluminum has the characteristics of strong corrosion, permeability and easy slagging. The working life of the liquid aluminum temperature measuring thermocouple is low and the stainless steel thermocouple protective tube can only last for about a week. Therefore, it has significance to study on the thermocouple protective tube with longevity.In the research, the corrosive experiment of cast iron, stainless steels and Ti-Al alloy in liquid aluminum maceration under the temperature of750℃was conducted firstly. Then the test sample of corrosion was conducted on the microstructure observation and the corrosion strength. Then the microstructure, micro-hardness and the corrosion strength were studied on the samples of nitrogen treatment. The result shows that the micro-hardness of the surface is evidently improved and the corrosion resistance to liquid aluminum is not apparent for the stainless steel samples after nitrogen treatment. However for the treated Ti-Al alloy samples, the Corrosion resistance in liquid Aluminum is evidently improved, then the process of corrosion is analyzed.Ti-Al2O3ceramic coatings were produced by using plasma spraying and laser remelting methods, and plasma tissue shows typical layer structure after spraying. After the treatment of the laser remelting, the coating structure becomes refined, dense, refinement, dense, well-distributed and the non-molten ceramic particle disappears and the remelted layer has no pores appearing. By using micro-hardness measurements, it is found that the degree of coating hardness increased significantly after laser remelting and the degree of hardness increased about1140HV. After studying on the transformation of laser remelted ceramic Ti-Al2O3ceramic layer.Through aluminum etching under the temperature of750℃,the corrosion resistance of the plasma sprayed coating in the aluminum liquid and the ineffective mechanisms have been studied. The results indicate that the corrosion resistance of Ti-Al2O3coating is high under high temperature and in the aluminum liquid environment. In the strong coating, there is unstable phase, inclusions, porosity and others, the failure is only demonstrated when the layer crack off in the aluminum liquid. After laser remelting, aluminum liquid corrosion resistant performance improves evidently and Ti-Al2O3ceramic coating can prevent contacting the molten aluminum directly to avoid Fe-Al spreading and reacting. |
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