Design And Fabrication Of Refractory Multicomponent High Entropy Alloys Coating With Laser Cladding

The mixing entropy of the high entropy alloy is higher than the melting entropy,and a simple solid solution phase is formed.The microstructure is simple,and generally does not tending to generate complex phases,such as intermetallic compounds,which have the characteristics of nano precipitates or amorphous structures.High entropy alloys generally have high hardness,high strength,high corrosion resistance,high wear resistance,high resistance,high heat resistance and other characteristics.At present,there is little research on the fine structure of the rapidly solidified high entropy alloy cladding coating.The development of high entropy alloy cladding coating is a good opportunity for the development of high efficiency and high added value.In this paper,the alloy system of the experiment was selected by the calculation of the empirical parameters and the first principles calculation method.The X ray diffraction patterns,the cohesive energy,the formation enthalpy,the elastic constants and moduli,the anisotropic parameters and the density states of distribution are calculated by the first principles calculations.The influence of mixing entropy on each parameter is studied.The laser cladding coating was prepared by the excellent combination of alloy elements.OM,SEM,EDS and XRD were used to analyze the morphology and microstructure of the coatings.The coatings were tested by micro hardness tester,and the corrosion resistance of the coating and substrate was tested by electrochemical workstation.The experimental results show that the calculated results are in good agreement with the experimental results.Through the comparison of the lattice constants,it can be concluded that this method is of high reliability,and the results have high accuracy.The difference of the lattice parameters of each alloy is mainly attributed to the effect of the lattice distortion.The cohesive energy and formation enthalpy are less than 0.The refractory high entropy alloy system has good mechanical stability,too.With the increase of entropy,the bulk modulus,shear modulus and Young's modulus are on the rise.We found that all of the alloys are ductile material.The anisotropy of bulk modulus is not strong.The zener ratio and elastic anisotropy of alloy are consistent with the isotropic structure.The values of the density of states at the Fermi level are all greater than zero.The density of states of each component has a low degree of overlap,and the combination between the component and the component is poor.It is proved that the alloy does not have a complex structure such as intermetallic compound.Based on the empirical parameters and the results of the first principles calculation,the TiZrVMoTa,TiZrVMoNb and TiZrVMoTaNb were used to laser cladding experiments.The parameters of the experiment are as follows:the spot diameter is 3.0mm,the scanning speed is 300mm/s,the laser cladding power is 4000W.The phase composition of the TiZrVMoTaNb coating is BCC solid solution and a small amount of HCP phase;The phase composition of the TiZrVMoNb coating is BCC solid solution and HCP phase.The phase composition of the TiZrVMoTa coating is BCC solid solution,HCP phase a small number of unknown phase.The organization of high entropy alloy coating are all dendrite structure.The TiZrVMoTaNb coating produces more "snowflake" grains,the grains are small and scattered,forming dense grain structure.The high melting point elements enriched in the dendrite.The hardness of the cladding layer increases from the bottom to the top.The range of the overall hardness of coating is smaller.High entropy alloy coating of TiZrVMoNb has obvious passivation.