Investigation On Preparation And Tribological Properties Of Plasma Sprayed High-entropy Alloy Coatings

High-entropy alloys have high strength,hardness,toughness and wear resistance due to their unique alloy design concept.Thermal spraying technology is one of the most effective technologies in the field of surface engineering to give new functions to the surface of materials.Plasma spraying technology was combined with high entropy alloy materials to study the relationship between microstructure and properties.It has high research value for the preparation technology,alloy structure and properties of high entropy alloy coatings,and has important guiding significance for promoting the application of high entropy alloys in the industrial field.This paper uses plasma spraying technology to prepare FeCoNiCr-based high-entropy alloy coatings as the research object,mainly to explore the structure and tribological behavior of FeCoNiCr-based high-entropy alloy coatings.The conclusions are as follows:(1)The effects of A1 content and annealing treatment on the microstructure evolution and tribological properties of FeCoNiCrSiAlx high-entropy alloy coatings were studied.The results show that the phase structure of the sprayed FeCoNiCrSiAlx coating layer was BCC phase with a minor amount of FCC phase.The addition of A1 has less influence on the phase of the sprayed coating than the annealed coating.Cr3Ni5Si2 intermetallic compounds are formed in the annealed coating.Under dry sliding condition,with the addition of Al element,the wear rate of the coating gradually decreases,and the annealed FeCoNiCrSiAl1.0 coating has the lowest wear rate,which is due to the increase in the BCC phase and Cr3NisSi2 phase in the coating.The main wear mechanism of the coating under dry sliding is flaking,while mild abrasive wear is the main wear mechanism of the coating under water lubrication.(2)The effects of H2 flow rate in plasma spraying parameters and annealing treatment on the microstructure and tribological properties of FeCoNiCrMn high-entropy alloy coatings were studied.The wear behavior of WC-Co balls in as-sprayed and annealed FeCoNiCrMn coatings under dry friction was compared.The results show that due to the volatilization and oxidation of the Mn element,a fluffy structure is formed on the surface of the sprayed coating.The phase structure of the coating consists of a single FCC phase and partial oxides.When the H2 flow rate increased from 3 L/min to 6 L/min,the wear rate of the coating was reduced by half.Annealing treatment can greatly improve the abrasion resistance and scratch resistance of the sprayed coatings.This is because increasing the H2 flow rate and annealing treatment can enhance the cohensive strength.(3)The effects of different elements(Al,Mo and Mn)on the structure and corrosion performance of FeCoNiCr-based high-entropy alloy coatings were studied.The three coatings were compared with GCr15 against friction under dry sliding and oil lubrication conditions.The friction and wear properties of the ball show that the phase structure of the FeCoNiCrAl coating includes the BCC phase,a small amount of FCC phase and oxides.The phase structure of the FeCoNiCrMo and FeCoNiCrMn coatings is composed of the FCC phase and oxide.Among the three coatings,the FeCoNiCrAl coating has the highest hardness value,the BCC phase structure and the hard phase oxide in the coating increase the hardness of the coating,and the FeCoNiCrMo coating has the best corrosion resistance.Under dry sliding condition,the wear mechanism of the FeCoNiCrAl high-entropy alloy coating is dominated by flaking,the FeCoNiCrMo high-entropy alloy coating is dominated by abrasive wear,the FeCoNiCrMn high-entropy alloy coating is mainly based on oxidative wear,so its wear resistance is the most excellent.