Microstructure evolution and electrochemical corrosion behavior of FeCrCoNiMoB1.1Si1.2 high-entropy alloy coating via laser cladding

Abstract

FeCrCoNiMoB1.1Si1.2 high entropy alloy (HEA) coatings were deposited onto TP347H steel using laser cladding with varying powers. Both HEA powder and coating form single FCC phases. When the power is 2600 W, the coating has higher crystallinity and fewer grain-boundary/lattice defects. The coating comprises a fusion zone and an HEA-coating zone. The fusion zone mainly comprises refined equiaxed grains, and its width is linearly positively correlated with laser power. Unlike other powers, the HEA coating zone with a power of 2600 W consists of a three-layer structure composed of columnar crystals, dendrites, and equiaxed crystals. The surface structure of the coating is primarily characterized by FCC dendrites. The surface structure of the coating with a power of 2600 W simultaneously contains FCC cellular crystals, with Mo enriched in dendrites and cellular; the coating exhibits excellent electrochemical corrosion performance with the minimum self-corrosion current(2.4 mu A/cm(2)), the highest self-corrosion potential(-0.2760 V). The impedance values (34,713.63 W center dot cm(2)) are 6.69 times, 2.71 times, and 4.1 times higher than 1800 W, 2200 W, and 3000 W, respectively. This can be attributed to the combined effects of a single FCC structure, a passivation film, and fewer grain-boundary and lattice defects in the coatings.