Microstructure, Properties And Preparation Of Al_x CoCrFeNiTi_0.5 High-entropy Alloy Coating By Laser Cladding

Steel is indispensable in engineering building materials with good mechanical properties and low price, but its poor high temperature wear resistance has limited the application in the most wear engineering fields. Heat resistant coatings are effective measures to improve the surface abrasion resistance of steel. High entropy alloy（HEA） includes five to thirteen principal elements at equimolar or near-equimolar compositions. Many HEAs have high wear and heat resistance. In this present study,AlxCoCrFeNiTi_0.5 coating was prepared by laser cladding technology on a pure iron matrix, with the aim of investigating alloy design, preparation, structure and properties of high entropy alloy coating using scanning electron microscopy（EDS）,X- ray diffraction, microhardness, friction and wear testing machine and other equipments. The research results indicated:The surface forming of the coating is good when the laser power, scanning speed and spot diameter is 3500 W, 300mm/min and 5mm respectively. The coating has highest hardness in the experimental coatings. At the same time it has low dilution rate and good metallurgical bonding layer between the coating and substrate.AlCoCrFeNiTi_0.5 high entropy alloy coatings are prepared by laser cladding with single-channel cladding. Microstructure observation results indicated that, Fe₂ Ti and Co4.00 with simple FCC solid solution structure form in the as-cast specimen. And it consists of coarse dendrites and primary α phases. After annealing at 900℃, AlFe with BCC structure and Al₈₀Cr₁₃Co₇ and Co₃Ti compounds appear. The microstructure is uniform finer ingredients typically spinodal decomposition microstructures with uniform composition, and there is no Ti segregation in the dendrites. The average Vickers micro-hardness of the as-annealed specimens is 989HV0.5, which is increased by 73.5% compared with that of the as-cast specimen. The abrasion resistance is reduced by 92.5%, the wear width is reduced by 50% and the friction coefficient is decreasede by 2.15% compared with that of the as-cast sample. The abrasion loss of Al_1.0CoCrFeNiTi_0.5 coating is reduced by 25% and the friction coefficient is reduced by 29% comparing with that of U75 V. The abrasion loss of the alloy coating is reduced by 85%, the wear width is reduced by 47 % and the friction coefficient is slightly reduced compared with that of AlCoCrFeNi high entropy alloy coating.