Microstructure Control and Wear, Corrosion Resistance of Laser Cladding FeCo_0.5CrNi_1.5B_0.5Nb_0.1High Entropy Alloy Coating

In view of the surface wear and corrosion problems of the vacuum pump rotor shaft in the actual working conditions, FeCo_0.5Cr Ni_1.5B_0.5Nb_0.1high entropy alloy coating was prepared on the surface of nodular cast iron（QT500-7） by laser cladding technology. The effects of different laser scanning speeds（300 mm/mi n, 400 mm/min, 500 mm/min, 600mm/min） on the phase composition, microstructure, microhardness, wear resistance and corrosion resistance of the coating were studied. The results show that with the increase of laser scanning speed, the coating undergoes local phase transformation, the grains are refined, and boride and carbide precipitate gradually between grains, which plays a role in precipitation strengthening. The microhardness, wear resistance and corrosion resistance of the coating first increase and then decrease with the increase of scanning speed. When the scanning speed is 500 mm/min, the coating phase is composed of FCC, Laves phase and a small amount of borides and carbides, with both strength and toughness. The microhardness of the coating is highest, which is 632.3 HV0.2, about 2.75 times than that of the substrate, and it has the best wear resistance and corrosion resistance.