Research On The Microstructure And Properties Of CoCrFeNiTi_x High Entropy Alloy Cladding Laye

Mechanical parts wear,corrosion,fatigue and other failures mainly occur on the surface of materials,in order to improve the service life of parts,the most effective way is to prepare high-performance modified layer on the surface of parts.High entropy alloy can be used as surface modification material to meet the requirements of industrial use because of its unique structure and structure with high strength,hardness,corrosion resistance,fatigue resistance,wear resistance and other excellent properties.In this paper,plasma cladding technology and laser cladding technology were used to prepare CoCrFeNiTi_x（x=0,0.2,0.4,0.6,0.8）high entropy alloy coating.The effect of Ti content on the microstructure and properties of the alloy coating was studied,and the relationship between coating composition,cladding method,cladding process and coating microstructure and properties was revealed.The main research work and results are as follows:1.Microstructure and properties of plasma cladding CoCrFeNiTi_x high entropy alloy:（1）the phase of cladding layer is a single face-centered cubic structure.（2）The average hardness of Ti0.0 cladding layer is 255.86 HV_0.3.The hardness increases with the increase of Ti content,and Ti0.8 is 1.77 times higher than Ti0.0.At Ti0.0,the friction coefficient is 0.32,and Ti0.8 is 1.52 times lower than Ti0.0.Compared with Ti0.0,the corrosion potential of Ti_x（x=0.2,0.4,0.6,0.8）moved to+20 mV,+60 mV,+74 mV,-29 mV respectively,indicating that appropriate Amount of Ti can improve the corrosion resistance of the cladding layer.2.Microstructure and properties of laser cladding CoCrFeNiTi_x high entropy alloy:（1）without Ti element added in the cladding layer,it shows a single FCC structure,and changes to FCC and BCC mixed structure with the increase of Ti element content;The microstructure of cladding layer changes from dendrite to equiaxed crystal.（2）Compared with Ti0.0,the average hardness of Ti0.8 cladding zone changes from 217.6HV_0.3 to 502.3 HV_0.3,an increase of 2.31 times;Compared with Ti0.0,the friction coefficient of Ti 0.8 decreased from 0.32 to 0.21,and the wear resistance was improved.The addition of Ti improves the corrosion resistance of the cladding layer,the corrosion potential of Ti0.6 is 339 mV higher than that of Ti0.0,and the corrosion current density decreases from 1.99×10^-6 A/cm² to 4.22×10^-7 A/cm².3.In the experiment of laser cladding CoCrFeNiTi_x high entropy alloy cladding layer,it was found that the addition of Ti element would affect the forming quality of the cladding layer,so the CoCrFeNiTi_0.8+CeO₂（0.5 wt.%,1.0 wt.%,1.5 wt.%）high entropy alloy coating was prepared by laser cladding process.The effects of CeO₂ on surface quality,microstructure and properties were studied:（1）the macro-quality of cladding layer was improved after adding three kinds of CeO₂.（2）The segregation degree of Ti element is improved and the grain is refined after adding CeO₂.（3）The microhardness of the cladding layer fluctuates little with the addition of CeO₂.The friction coefficients of 0.5 wt.%,1.0 wt.%and 1.5 wt.%CeO₂ were reduced by 29.3%,39.0%and 41.5%,respectively,and the antifriction performance was improved.When CeO₂ content is 0.5 wt.%,1.0 wt.%and 1.5 wt.%,the corrosion potential of the cladding layer is 172 mV,149 mV and 152 mV,and the corrosion resistance is improved.