Research on Anti-Oxidation and Wear-Resistance Co–Cr–Fe–Nb–Ni High Entropy Alloys Coatings Prepared by Laser Cladding

Oxidation and wear have been confirmed to be a great threat to the metals at high temperatures, for instance, in the fields of power, petrochemical industry, weapon, and aerospace. A novel Co–Cr–Fe–Nb–Ni high-entropy alloy coating was designed and manufactured by laser cladding, which was composed of toughness FCC and hardness Laves phase. The Cr atoms dissolved into the FCC phase, while the Si atoms doped into the Laves phase by replacing the Nb atoms. In the oxidation process, the coating experienced mainly the selective oxidation of the Cr and Nb. The oxidation of Si in the Laves phase replaced the Nb, producing a more stable (Cr, Si)Ox at the interface and delaying the internal diffusion of oxygen. The addition of Ce improved the compactness and bonding strength of the Cr2O3 oxide film. The hardness of Co–Cr–Fe–Nb–Ni coatings was determined by the Laves phase and the MC phase, which precipitated by the diffusion of Nb and C and decreased the Laves content. The wear mechanism changed from abrasive wear to oxidation wear as temperature increased. The Co–Cr–Fe–Nb–Ni HEAs coatings exhibited superior performance of anti-oxidation and wear resistance compared to electroplated hard Cr coating at high temperature.