High-entropy Alloy Coating Prepareed By Ultrasound Composite TIG Arc

In this paper,two flux-cored wires with different compositions were prepared.FeCrMnCuNi and Fe₃NiMoNbNi_x high-entropy alloy cladding coatings were prepared by ultrasonic assisted arc cladding.Then the effects of ultrasonic and several overlapping cladding on the structure and properties of the coatings were studied,and the wear properties of Fe₃NiMoNbNi_x high-entropy alloy cladding coatings were explored.Firstly,FeCrMnCuNi high entropy alloy cladding coating was prepared.Compareing with 304 steel,its hardness increased by 13%.And the structure of FeCrMnCuNi high-entropy alloys and the alloys after ultrasonic treatment were observed by electron probe micro-analyzer（EPMA）.A serious inhomogeneity of composition in the high-entropy alloys was observed.And there was a great difference between dendritic zones and equiaxed zones,and more FCC2 phases were precipitated along the grain boundaries,which cause the reduce of the hardness of the material;with the joining of ultrasound,The microstructure of the high-entropy alloy was homogenized and the microhardness was improved from190HV to 197HV.Then,the high-entropy structure of Fe3NiMoNbNix（x=0,0.5,1）system was observed by EPMA.With the increase content of Ni,the high-entropy face-centered cubic（FCC）structure gradually precipitated on the matrix of the body-centered cubic（BCC）crystal structure,and eventually completely replaced the matrix structure.The microhardness of the obtained high-entropy alloy structure was greatly improved compared with that of the base metal,getting the high-entropy alloy with 430HV microhardness at last.Finally,the effect of multi-pass cladding on the structure of high-entropy alloy and the effect of ultrasound on the structure of multi-pass cladding were analyzed.The results show that with the increase of passes,the amplitude-modulated decomposition phenomenon gradually occurs in the grain of the alloy,which is gradually decomposed into FCC1 phase and FCC2 phase,which causing the microhardness of the coating increases from 420HV to 450HV and then decreases to 420HV.Ultrasound can affect the morphology of the phases after the amplitude-modulated decomposition by changing the element distribution of the coating,resulting in the change of the structure and properties of the alloy after multi-pass cladding,which greatly improves the friction and wear properties of the coating.Compared with base metal,friction coefficient increases from 0.05 to 0.2.