(BCSiAlCr)N_x High Entropy Alloy Film Microstructure And Corrosion Resistance Performance Study

High entropy alloy was first proposed by Yeh et al.It refers to an alloy system containing five or more main elements with equal or approximate molar ratio.Because the mixing of multi main elements of high entropy alloy will lead to high mixing entropy,serious lattice distortion,slow diffusion effect and cocktail effect,it shows different characteristics,such as excellent mechanical properties,thermal stability,corrosion resistance,wear resistance,oxidation resistance and compressive strength.High entropy alloy coatings/films usually show similar properties to bulk high entropy alloys,or even better than bulk high entropy alloys,and have great potential in many application fields.Therefore,in this thesis,BCSiAlCr high entropy alloy is selected as the target,and the high entropy alloy film is prepared by DC magnetron sputtering system.The effect of nitrogen flow on the microstructure and microstructure of（BCSiAlCr）N_xhigh entropy alloy film is studied.The corrosion resistance of（BCSiAlCr）N_xhigh entropy alloy film in 3.5%Na Cl solution and 0.5 M/L sulfuric acid solution is tested by electrochemical corrosion test method,The corrosion resistance mechanism of（BCSiAlCr）N_xhigh entropy alloy films prepared under different nitrogen flow rates in different corrosion solutions was studied.In detail,（BCSiAlCr）N_xhigh entropy alloy films were deposited on Si（100）substrate and 304 stainless steel substrates by DC magnetron sputtering.Firstly,the content of each element in the high entropy alloy film was measured by XPS.It was found that the five elements of B,C,Si,Al and Cr in the high entropy alloy film were not equal molar ratio and near molar ratio.This was due to the sputtering effect,which made the lighter and heavier substances have higher backscattering possibility,so that the content of each element in the film did not have the characteristics of equal molar ratio and near molar ratio.SEM analysis showed that with the increase of nitrogen content in high entropy alloy film,the columnar crystal structure providing diffusion channel for corrosion solution in the film disappears,the crystal structure of the film becomed more uniform and dense,and the cavities and defects on the surface of the film were reduced.The crystal structure of（BCSiAlCr）N_xhigh entropy alloy nitride film was analyzed by XRD and TEM.With the increase of nitrogen flow,the amorphous degree of the film increased in XRD.At the same time,the bright field image of TEM and the wide halo in the corresponding electron diffraction pattern also showed that the film was mainly amorphous structure and transformed to amorphous phase.The corrosion resistance of high entropy alloy film,including potentiodynamic polarization curve,potentiostatic polarization curve and impedance characteristics,was studied by electrochemical workstation.The experimental results showed that HE3 high entropy alloy film prepared under the maximum nitrogen flow had the best corrosion resistance compared with 304 stainless steel sample in 3.5%Na Cl solution,and its corrosion current density(i_corr)was the lowest of 0.0311μA/cm²,with the highest corrosion potential of-37.557 mv,indicating that He3 high entropy alloy film has the minimum corrosion rate and excellent stability.In the corrosion resistance experiment of the film in 0.5 M/L sulfuric acid solution,HE3 high entropy alloy film also showed the most excellent corrosion resistance,with the minimum corrosion current density(i_corr)of 0.0795μA/cm²,with the highest corrosion potential of 159.78 mv,showing the best corrosion resistance.HE3 high entropy alloy film has the best corrosion resistance in both corrosion solutions,which is mainly due to the increase of nitrogen content in the film,the increase of amorphous degree of the film,the denser structure of the film,the disappearance of surface defects and cavities,and the effective improvement of the corrosion resistance of the film.