Electrodeposition Preparation Process And Deposition Mechanism Of Fe-Co-Ni-Cr Quaternary High-entropy Alloy Coating

The preparation process of high-entropy alloy film is usually magnetron sputtering,vapor deposition and other methods,which have low productivity and high requirements for equipment.This paper studies the preparation of FeCoNiCr high-entropy alloy coating by electrodeposition,and designs the electroplating formula of FeCoNiCr alloy independently.The experiment determined the main salt concentration,deposition temperature,p H value,additive content,ascorbic acid concentration,current density in the plating solution by controlling single factor variables,and finally determined the best electrodeposition process and formula for preparing FeCoNiCr high-entropy alloy coating It is:CrCl₃·6H₂O 80 g/L,NiCl₃·6H₂O 30 g/L,NiCl₃·6H₂O 4 g/L,FeCl₂·4H₂O 2.5 g/L,citric acid 120 g/L,ascorbic acid 5 g/L,H₃BO₃ 20 g/L;The process parameters are:cathode current density 13-15 A/dm²,temperature 25±5℃,p H value 2-2.5.The macroscopic gloss of the coating is relatively high.SEM scanning reveals that there are a few microcracks on the microscopic level,the size of the deposited cells is uniform,and the elements in the coating have no segregation and enrichment.Experiments have found that Ni inhibits the deposition of Cr and makes the deposited bag-like structure larger;the increase of Fe makes the coating yellow,easy to oxidize,and inhibits the deposition of Cr and Ni;the increase of Cr content will cause cracks in the coating.Cr is easier to deposit below 30℃,and the content of Cr is extremely low above40℃.The p H value can only be between 1-3,otherwise Cr cannot be deposited.Ascorbic acid inhibits Fe and Co,and promotes the deposition of Cr.Citric acid can promote Cl^-in CrCl₃ to replace H₂O molecules in[Cr（H₂O）₆]³⁺to form[Cr（H₂O）₅Cl]²⁺,[Cr（H₂O）₄Cl₂]⁺,and promote the reduction of Cr.Increase the Cr content in the alloy coating,and too much citric acid will cause the plating solution to be polarized and more pores on the coating surface.The polarization curve of the alloy deposition was measured and it was found that there was a maximum current density of 16.5 A/dm² during the alloy electrodeposition,and the cathode potential was-2.26 V at this time.An electrochemical workstation was used to measure impedance spectra at different deposition potentials,and it was found that when the initial deposition potential of the reaction was less than-0.7 V,the solution did not undergo electrodeposition reaction,but there was an electrochemical reaction,and the reaction was controlled by electrochemical steps.When the deposition potential is between-0.7 V and-1.26 V,the elements begin to deposit.The reaction is not only controlled by the ion diffusion rate,but also by the charge exchange rate.When the deposition potential is between-1.26 V and-2.78 V,the deposition of various elements in the plating solution gradually changes from single gradual deposition to co-deposition,the cathodic polarization becomes stronger and stronger,the resistance of the electrochemical reaction is very low,but the transmission The resistance of the qualitative step does not change.After the potential exceeds the limit current density,the resistance of the electrochemical reaction disappears.