Preparation And Properties Of CoCu_xFeNiTi-M System High Entropy Alloy Coatings

The working environment of the shearer and roadheader is wicked,which leads to the service life of the cutter greatly reduced,and significantly increases the maintenance cost of the shearer.In this paper,a new type of CoCu_xFeNiTi-M high entropy alloy coatings were prepared by laser cladding on the surface of the pick.The preparation process was optimized by single factor test.The effects of Cu and Mo content on the mechanical properties of CoCu_xFeNiTi-M high entropy alloys were studied by first principles calculation,which provided a basis for subsequent experimental research.The microstructure,phase composition and element distribution of the coatings were analyzed by SEM,XRD and EDS,the influence of Cu and Mo content on the microstructure and phase composition of the coating was investigated.The effects of Cu and Mo content on the macroscopic properties of CoCu_xFeNiTi-M high entropy alloy coatings were studied by microhardness,dry friction and electrochemical corrosion tests.the mechanism of coating wear and corrosion failure was revealed.The results are as follows:(1)The preparation process of the coating was selected as laser power 700W and scanning speed 6mm/s.(2)The phase composition of CoCuFeNiTi high entropy alloy coating is mainly FCC phase and Cu₄Ti intermetallic compound.The microstructure of the coating presents dendritic structure,and Cu element will be enriched in the interdendritic and form micro-nano Cu-rich phase.The microhardness of the coating is 438.83HV.the wear loss is about half of the substrate.The wear mechanism of the coating is mainly adhesive wear,and with a small amount of abrasive particles.CoCuFeNiTi high entropy alloy coating showed better corrosion resistance than substrate in the acid solution of p H=4 and 3.5wt.%Na Cl solution.(3)First-principles calculations show that with the increase of Cu content,the lattice constant of CoCu_xFeNiTi high entropy alloy is increased,the cell density is decreased gradually,the strength and hardness are decreased,and the plasticity is increased.The analysis of the coating shows that with the increase of Cu content,the content of intermetallic compounds in the coating are decreased,the content of FCC phase is increased.The lattice distortion is increased by the solid solution of Cu,which leads to the increase of the lattice constant of the FCC phase and the increase of the Cu-rich phase in the coating;The microhardness and wear resistance of the coating are decreased,and the wear mechanism changed from abrasive wear to adhesive wear.With the increase of Cu content,the corrosion resistance of the coating in acidic solution was increased,while that in 3.5 wt.%Na Cl solution was reduced.(4)First-principles calculations show that with the increase of Mo content,the constant and cell density of CoCuFeNiTi Mo_x high entropy alloy is increased,the hardness is increased,the plasticity is decreased,and the alloy changes from ductile material to brittle material.The analysis of the coating shows that with the increase of Mo content,the coating changed from FCC phase to FCC+BCC phase,the type of intermetallic compounds in the coating are changed,the segregation of Cu element is decreased,and the hardness and wear resistance of the coating are increased.The wear mechanism of the coating changed from adhesive wear to abrasive wear.CoCuFeNiTi Mo_0.4 high entropy alloy coatings has excellent corrosion resistance in acidic solution,and CoCuFeNiTi Mo_0.8high entropy alloy coatings has better corrosion resistance in 3.5 wt.%Na Cl solution.