| The concept of High-Entropy Alloy(HEA) has been widely used since it was put forward. HEA mainly refers to a kind of alloy in which not only the number of major elements is greater than 5 but also the atomic percentage of each of the main elements is 5% to 35 %. Besides, none of atomic percent of the major elements is more than 50% and becomes the only major elements. Due to the excellent properties such as high hardness, high strength, wear resistance, corrosion resistance, high temperature oxidation and unique magnetic properties, which are an accomplishment unmatched by traditional alloy materials, HEA has a promising application and also a large number of high-tech materials can be developed by it.Through FeConNiCuCr_x(x=0,0.21,1.0,2.15,3) HEAs which were prepared by WK-?vacuum non-consumable arc furnace, the thesis focuses on studying the alloy phase structure, micro-structure and composition of cast HEAs by XRD,SEM and EDS, finding out that the alloy has a simple FCC structure, and at the same time, with the increase of Cr content, the structure of cast HEAs alloy changed into BCC + FCC structure. What's more, the micro-structure of cast HEAs tissue morphology is a typical dendritic structure, and Cu element are rich in dendrites while other elements in the interdendritic is uniform distribution.Based on a self-built electric spark-computer integrated deposition system(ES-CIDS), through the numerical control of the deposition method, using parameters such as the welding deposition strategy of spacing type spot, the HEAs costing of 1, 3 and 5 layers of FeConNiCuCr_x(x=0,0.21,1.0,2.15,3) HEAs is prepared on the surface of 45 steel. The microstructure of the high entropy alloy coating was studied by XRD, SEM and EDS.It turns out that the dense of HEAs coatings is relatively better: the thickness of the 1 layer is about 10 ?m, and the thickness of the 3 layers is about 17 ?m and the thickness of the 5 layers is approximately 25 ?m. The XRD tests on coating surface and cross section indicate that the coating of the first deposited layer has a simple FCC + BCC structure and the coating gradually transits to FCC structure. Through SEM observation, the natural topography of the coating is sputtering like pattern, and the cross-sectional structure of the coating is mainly composed of dendritic structure. Through the analysis of EDS, it can be found that the amount of Fe element in the coating is higher than that in the actual configuration, which is caused by a hot melting and cooling effect of HEA and the base material 45 steel.Corrosion resistance in the aqueous solution of 3.5wt.% NaCl justifies that in FeConNiCuCr_x(x=0,0.21,1.0,2.15,3)HEAs and in 45 steel samples with HEAs coatings of FeConNiCuCr_x(x=0,0.21,1.0,2.15,3) prepared by the numerical control deposition strategy, the more increasing of Cr element, the decreasing of Cu element will be, and meanwhile the corrosion resistance gradually increases. Both of the corrosion resistance in above two samples are superior to 45 steel, and this is because the coated specimens containing high passive film formed by Cr oxide, which can improve the corrosion resistance of coatings. Also, it can be found that the increase of the thickness of the coating helps to improve the corrosion resistance, and this is mainly because with the increasing of deposition, the uniformity and anti-erosion ability of coating will be enhanced. |
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