Microstructure And Corrosion Resistance Of AlCoCrFeNi_xMo_y High Entropy Alloy Coating By Laser Cladding

Traditional alloys have one or two main elements.Ye Jun wei et al.developed a new design method for alloy which was different from the traditional alloy,and proposed the concept of high-entropy alloys for the first time.The structure of the alloy is usually simple solid solution.High entropy alloys have four effects（high entropy effect,hysteresis diffusion effect,lattice distortion effect and"cocktail effect"）,so high entropy alloys have excellent properties,such as high strength,high wear resistance and corrosion resistance,etc.With the rapid development of modern industry,the corrosion and wear of machinery and equipment is an inevitable major loss.Therefore,adding Ni and Mo elements with pitting resistance and high hardness to traditional alloys is expected to become a new type of corrosion-resistant high-entropy alloy material.The high entropy alloy coatings of AlCoCrFeNi_xMo（x=0,0.5,1.0,1.5,2.0）and AlCoCrFeNi_0.5Mo_y（y=0.25,0.5,0.75）have been prepared on the surface of pure iron by laser cladding.The microstructure and micro-area composition of the coatings were analyzed by SEM and X-ray diffractometer.The hardness of the coastings was tested by Vickers hardness tester.The corrosion resistance of the coatings was studied by three-electrode electrochemical workstation.The research results indicated that:（1）Microstructure of AlCoCrFeNi_xMo single-pass coating consisted of the BCC,the B2 and the sigma phase.When the content of Ni was x=0.5 and x=1.0,the coating formed uniform and fine nanometer structure.The hardness of AlCoCrFeNi_0.5Mo coating was 1008 HV₁.（2）The microstructure of AlCoCrFeNi_xMo dual-pass coating changed from BCC+σphase to FCC+BCC+B2 phase with the increasing of Ni content.When Ni content was x=0 and x=0.5,the microstructure of the coating was fine and homogeneous,and when Ni content was x=1.5 and x=2.0,the coating forms microstructure of acicular ferrite.The hardness of AlCoCrFeNi_0.5Mo coating was 973HV₁.When the content of Ni was x=0.5,the self-corrosion potential of the coating was the highest(E_corr=-0.4201 V),the self-corrosion current density was the lowest(I_corr=0.6411×10^-4 m A/cm²),and the corrosion resistance was the best in the solution of 3.5 wt.%Na Cl.（3）Microstructure of AlCoCrFeNi_0.5Mo_y single-pass coating consisted of BCC+B2+σphase.The microstructure of the coating changed from equiaxed to dendrite with the increasing of Mo content.When the content of Mo was x=0.75,the hardness of the coating was 906 HV₁.When the content of Mo was y=0.25,the self-corrosion potential of the coating was the highest(E_corr=-0.2347 V),the self-corrosion current density was the lowest(I_corr=0.6956×10^-5 m A/cm²),and the corrosion resistance was the best in the solution of 3.5 wt.%Na Cl.（4）Microstructure of AlCoCrFeNi_0.5Mo_y dual-pass coating consisted of the BCC,the B2 and the sigma phase.The hardness of Al Co Cr Fe Mo_0.75Ni_0.5 coating was 909HV₁.When the content of Mo was y=0.25,the corrosion resistance of the coating was the best in the solution of 3.5 wt.%Na Cl.