| Currently, the Accelerator Driven Subcritical System(ADS) is the most powerful tools which disposal of nuclear waste. But the materials of nuclear equipment must be under the extreme condition of irradiation, corrosion, high temperature, resulting in the surface properties of the materials of nuclear equipment need to be further improved in the ADS.In order to explore new methods to improve the performance of the material surface, Cr-Fe-Al-Ti composite powder system was chosen through a large number of previous experimental work in this paper. Flame spraying coating was successfully fabricated by flame spraying on the materials of nuclear equipment. The flame spraying coatings was remelted by laser, and the composite ceramic coatings was successfully fabricated by optimizing the process parameters and the coating composition ratios. Macro morphologise of laser remelted coatings was described by stereo microscope with different laser processing parameters; Phase composition, microstructure and microhardness of flame spraying coatings and remelting coatings were analyzed by means of XRD, SEM, EDS respectively, the main research results are as follows:(1)The Cr-Fe-Al-Ti system of composite powder was prepared by mixing, heating and stirring, broking. Flame sprayed coatings showed obvious layered structure, maintained good mechanical bonding to the substrate, has some pores and micro-cracks. Analyzed macro morphologise of laser remelted coatings(powder mass ratio of Ti, Fe Al50, Cr Fe is 1:2:2) by multiple processing parameters, the optimized processing parameters are follows: laser power P=1.4 k W, scanning speed V=6 mm/s, spot diameter D=2 mm.(2)With the optimized process parameters, laser remelted coatings with smooth surface, no pores and cracks is obtained. The microstructure possess more dense and uniform with a thickness of about 120 μm and a good metallurgical bonding to the substrate. Three kinds of microstructure of laser remelted coatings, in situ synthesized by laser cladding, contain Al2O3, Ti O2 hard ceramic phase. Cellular grain, columnar grain is distributed diffusely in the microstructure. Compared with the flame sprayed coatings and the substrate, the micro-hardness of laser remelted coatings increase significantly.(3)With the optimized process parameters, the different coating composition ratios of the laser remelted coatings was remelted by laser rapid scanning. The results show that: Three kinds of microstructure of composite coatings possess more dense and uniform. A good metallurgical bonding is formed between the composite coatings and the substrate. Coatings diffusely distribute some Cr2O3, Al2O3, Cr7C3 bulk, dendritic and hard ceramic phase in the black area of the microstructure. The amount of phase varies with the chemical composition of composite powders. Compared with the substrate, three kinds of micro-hardness of composite coatings increase significantly. When powder mass ratio of Ti, Fe Al50, Cr Fe is 1:2:2, Composite ceramic coating showed the best quality of morphology and the highest average microhardness. |
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