The Study Of FeCoCrNiB_x High-entropy Alloy Coating Prepared By Laser Cladding For The Microstructure And Property

Multi-element high-entropy alloys have a potential for acting as a coating due to their superior performance. Consequently, it is not only can take advantage of the excellent properties of high-entropy alloy, but also can save resources and reduce the cost. Therefore, it is significantly important to prepared high-entropy alloy coatings for industrial application. Here, the FeCoCrNiBx (x=0.5,0.75,1.0,1.25, the subscript is mole number) high-entropy alloy coatings on the Q235 steel were prepared by laser cladding. The morphology, phase composition and microstructure of the high-entropy alloy coatings were investigated by optical microscope, scanning electron microscope and X-ray diffraction, while the hardness, wear resistance and corrosion resistance of coatings were respectively measured by vickers hardness tester, wear tester and electrochemical workstation. The effects of the contents of B on microstructure and properties of high-entropy alloy coatings were studied. Furthermore, the effects of high-temperature annealing on microstructure and properties of FeCoCrNiBo 5 and FeCoCrNiB1.25 high-entropy alloy coatings were also investigated. The main results show that:The phase composition of FeCoCrNiBx high-entropy alloy coatings is simple. With the increase of B content, the alloys have a change in phase structure from FCC solid solution to a combination of FCC solid solution and M3B phase, and the M3B phase gradually increased. When x=0.5 the microstructure exhibits typical dendrite morphology, where interdendrite microstructure is eutectic structure. With the increase of B content the strip-like M3B phase appeared, and it gradually grows up to blocky structure.With increasing the amount of B, the hardness of FeCoCrNiBx high-entropy alloy coating increased, ranging from 447HV to 848HV. And the wear resistance was enhanced with the increase of B content. In 3.5 wt.% NaCl solution, the corrosion resistance of FeCoCrNiBx high-entropy alloy coating is better than that of the S304 stainless steel. And when x=1.0 the corrosion resistance is the best. In 10 wt.% NaOH solution, the corrosion resistance of FeCoCrNiB high-entropy alloy coating is the best. In 0.5 mol/L H2SO4 solution, the corrosion resistance of FeCoCrNiBx high-entropy alloy coating is better than that of the 304 stainless steel, and when x=0.5 the corrosion resistance is the best.Along with the rising of annealing temperature, the M3B phase precipitated in FeCoCrNiB0.5 high-entropy alloy coating, resulting into obvious dispersion strengthening. So the FeCoCrNiB0.5 high-entropy alloy coating exhibits excellent resistance to high temperature softening, after annealing at 800℃ for the microhardness had no obviously declined. While the FeCoCrNiB1.25 high-entropy alloy coating annealed at different temperature, the solid-solution strengthening is significantly higher than the dispersion strengthening. Therefore the resistance to high temperature softening of FeCoCrNiB1.25 high-entropy alloy is worse than that of FeCoCrNiB0.5 high-entropy alloy.