目的 采用超音速火焰喷涂技术在P12钢表面制备45CT和NiCr/Cr3C2涂层，研究两种涂层样品的热腐蚀行为和机理。方法 将样品表面涂覆75%Na2SO4+25%NaCl（质量配比）混合盐膜后，置于650 ℃含0.15%SO2（体积分数）的模拟烟气中进行腐蚀，间隔一定时间取出样品进行质量称取，获得腐蚀动力学曲线。采用XRD、SEM/EDS对喷涂层和热腐蚀产物的成分、形貌、物相进行分析。结果 采用超音速火焰喷涂制备的涂层结构致密、孔隙率低。腐蚀过程中样品整体表现为增重，但增重过程中有失重，NiCr/Cr3C2后期失重比45CT严重。 45CT和NiCr/Cr3C2涂层均生成了耐蚀性良好的致密Cr2O3，而NiCr/Cr3C2涂层样品在涂层/基体界面还生成了氧化物和硫化物层，易导致涂层与基体界面弱结合。结论 在650 ℃含0.15%SO2的模拟烟气条件下，45CT涂层样品表现出了比NiCr/Cr3C2更好的抗热腐蚀性能。

The work aims to study hot corrosion behavior and mechanism of 45CT and NiCr/Cr3C2 coating samples by preparing the two coatings on P12 steel by adopting high velocity oxygen fuel spray technology. The samples were coated with a film of mixed salts 75%Na2SO4+25%NaCl (mass fraction), then placed in simulated flue gas containing 0.15%SO2 at 650 ℃, and later taken out at certain interval to weigh mass and obtain corrosion kinetics curve. Composition, structure and phase of the sprayed coatings and hot corrosion products were analyzed with XRD and SEM/EDS. The coatings prepared by HVOF featured in compactness and low porosity. The samples experienced mass gain in the corrosion process, but both were subject to mass loss during mass gain. Mass loss of NiCr/Cr3C2 was worse than that 45CT subsequently. Corrosion products of 45CT and NiCr/Cr3C2 were identified as Cr2O3, NiO and NiCr2O4. A dense Cr2O3-rich scale formed on these two kind of coatings sample surface. NiCr/Cr3C2 coating samples generated oxide and sulfide layers on the substrate/coating interface, which might easily led to weak bonding between in the coating and substrate. Corrosion resistance of 45CT coating sample is better than that of NiCr/Cr3C2 coating in the 0.15% SO2 simulated flue gas at 650 ℃.