Microstructure And Properties Of Laser Cladding CoCrFeNiSi_x High-entropy Alloy Coatings

The fatigue,wear,corrosion and other failures of mechanical parts mostly occur on the surface of the material,and the surface enhancement coating prepared by laser cladding technology can significantly improve the microhardness,wear resistance,corrosion resistance,and oxidation resistance of the substrate surface.Since high-entropy alloys have many excellent properties,laser cladding technology can be used to prepare high-entropy alloy coatings on the surface of the material to improve the service life of mechanical parts.CoCrFeNi high-entropy alloy has good plasticity and corrosion resistance,but its hardness is low,which affects its application range.As a typical self-fluxing non-metallic element,Si not only improves the forming performance of the coating,but also strengthens it.In this paper,a CoCrFeNiSix（x=0.0,0.5,1.0,1.5,2.0）high-entropy alloy coating was prepared on 45 steel by laser cladding technology,and the influence of Si content on its structure and performance was studied,and the alloy coating was carried out separately Annealing at 600℃,800℃,and 1000℃,the structure and performance changes after different annealing temperatures were studied.The main findings are as follows:（1）The addition of Si in the laser cladding CoCrFeNiSix alloy coating can improve the formability of the coating.As the Si content increases,the wettability between the coating and the substrate increases,and the dilution rate first increases and then decreases.（2）The addition of Si element will cause the phase and structure of the coating to change.By adjusting the Si content in the coating,it is found that the coating is transformed from a single fcc phase(Si_0.0)to a mixed phase of fcc and bcc phases(Si_0.5.,Si_1.0,Si_2.0),and finally all transformed into bcc phase(Si_2.0).The coating structure changes from equiaxed(Si_0.0)to dendrite(Si_0.5,Si_1.0)with the addition of Si element,and finally transformed into equiaxed(Si_1.5,Si_2.0),the overall grain Refinement.（3）The addition of Si element will increase the hardness of the coating.When the Si content is 0,the microhardness of the coating will be 452.1HV_0.5,and then the hardness of the coating will increase with the increase of Si content,to Si_2.0can reach586.5HV_0.5.In addition,the wear resistance and anti-friction properties of the alloy are also improved with the increase of Si content（4）The addition of Si element improves the corrosion resistance of the alloy coating.The corrosion potential of the coating increases with the addition of Si element.Si_2.0is positively shifted by about 160m V compared with Si_0.0,and the corrosion tendency becomes smaller.The corrosion current density decreases with the increase of Si content,from 1.17×10^-6to 6.06×10^-7A/cm²,and the corrosion rate decreases.The corrosion morphology of the coating changes from general corrosion to local corrosion（5）CoCrFeNi,CoCrFeNiSi,CoCrFeNiSi_2.0high-entropy alloy coatings were annealed at 600℃,800℃,and 1000℃,and no new phases were found to be formed.The hardness and wear resistance of the CoCrFeNi coating decrease with the increase of annealing temperature,and are significantly lower than before heat treatment.The hardness and wear resistance of CoCrFeNiSi coating are less affected by temperature.The hardness and wear resistance of CoCrFeNiSi_2.0coating are significantly improved compared to before heat treatment,and its performance will increase slightly with the increase of annealing temperature.