Microstructural Characterization and High-Temperature Oxidation Behavior of NiCrAlY/YSZ Coating on 20G Steel

To improve the high-temperature oxidation resistance of 20G steel, NiCrAlY and yttria-stabilized zirconia (YSZ) coatings were deposited via plasma spraying. Subsequently, high-temperature cyclic oxidation analysis was performed at 900 °C for a total duration of 80 h (10 cycles) to examine the oxidation kinetics of 20G steel, NiCrAlY, and NiCrAlY/YSZ coatings. The NiCrAlY/YSZ coating demonstrated the lowest oxidation rate constant (Kp = 1.3843 × 102 mg2·cm−4·h−1), a thermally grown oxide (TGO) layer, and showed the lowest oxidation resistance compared with the NiCrAlY bond coating and 20G steel. Characterization analysis revealed the formation of a continuous and dense α-Al2O3 layer that acts as an effective diffusion barrier, impeding both inward oxygen diffusion and outward migration of metallic ions. The improved high-temperature oxidation resistance is mainly attributed to the synergistic interaction between the NiCrAlY/YSZ coating and 20G steel. The developed coating structure is beneficial for high-temperature boiler tubes, heat exchangers, and other power plant components, where improved oxidation resistance can significantly enhance service life.