实际锅炉工况 750°C 下热喷涂 Ni–Cr 复合涂层在 SA516 锅炉钢上的冲蚀-腐蚀性能

High-temperature erosion–corrosion (E-C) is a major cause of material degradation in coal-fired thermal power plants, resulting in reduced component life and increased maintenance costs. Thermal spray coatings provide an effective surface modification route for improving the durability of boiler steels exposed to aggressive high-temperature environments. In the present study, Ni–20Cr and ceramic-reinforced Ni–20Cr composite coatings containing 40 wt% TiC or TiN were deposited on SA516 Grade 70 steel using high-velocity oxy-fuel (HVOF) and plasma spraying techniques. The coatings were characterized in terms of their phase composition, microstructure, elemental distribution, porosity, and microhardness using XRD, SEM/EDS, elemental mapping, and microhardness measurements. To assess their performance under representative boiler operating conditions, coated and uncoated specimens were exposed to 15 thermal cycles in the superheater region. All coatings substantially reduced E-C degradation compared with the uncoated steel. The TiC-reinforced coatings showed the highest resistance, with degradation reductions of up to 95.25% and 93.85% for HVOF- and plasma-sprayed coatings, respectively. Their superior performance was associated with higher microhardness (approximately 680 HV), reduced porosity, and the development of protective oxide phases, including Cr₂O₃, NiTiO₃, and NiCr₂O₄. Overall, the results demonstrate that TiC- and TiN-reinforced Ni–20Cr coatings can significantly improve the resistance of SA516 Grade 70 steel to high-temperature erosion–corrosion under actual boiler operating conditions.