Corrosion Resistance to Molten Zinc of a Novel FeB-10 Mo-12 Al0.25FeNiCoCr Cermet and Coating

A novel FeB-10 wt.% Mo-12 wt.% Al0.25FeNiCoCr (denoted as FeB-10 Mo-12 HEA) cermet and coating were prepared by spark plasma sintering (SPS) and an activated combustion high-velocity air fuel (AC-HVAF) spraying process, respectively. The microstructure, phase compositions, density, microhardness, thermal shock and corrosion resistance of the cermet and coating to molten zinc were characterized in detail. The results show that the phase composition of the coating was the same as that of the cermet, which was composed of an (Fe, Al, Ni, Co, Cr)B solid solution, an (Fe, Al, Ni, Co, Cr)2B solid solution and a Mo phase. The brittleness of FeB and Fe2B was reduced by the Al, Fe, Ni, Co and Cr elements of the high-entropy alloy that was dissolved into them. The addition of Mo, which did not undergo a eutectic reaction with Zn at 450 °C, and the corrosion products (δ phase) increased the corrosion resistance of the novel cermet. Compared with the cermet that was prepared by SPS, the coating that was prepared by AC-HVAF had a lower density, lower microhardness value and worse corrosion resistance to molten zinc because of the layered structure of the coating, in which cracks could form and propagate easily under the action of thermal stress.