引用本文:张盼盼,孙宇海,孙磊,李波,张群莉,姚建华.激光合金化掺杂TiC对等离子喷涂8YSZ热障涂层热腐蚀行为的影响*[J].中国表面工程,2023,36(6):126~134
ZHANG Panpan,SUN Yuhai,SUN Lei,LI Bo,ZHANG Qunli,YAO Jianhua.Effect of Laser Alloying TiC Doping on the Hot Corrosion Behavior of Plasma Sprayed 8YSZ Thermal Barrier Coatings[J].China Surface Engineering,2023,36(6):126~134
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激光合金化掺杂TiC对等离子喷涂8YSZ热障涂层热腐蚀行为的影响*
张盼盼1,2,3, 孙宇海1,2,3, 孙磊1,2,3, 李波1,2,3, 张群莉1,2,3, 姚建华1,2,3
1.浙江工业大学机械工程学院 杭州 310023;2.浙江工业大学激光先进制造研究院 杭州 310023;3.浙江工业大学高端激光制造装备协同创新中心 杭州 310023
摘要:
传统的等离子喷涂热障涂层在高温环境下服役易受熔融腐蚀盐渗透而过早剥落失效，研究激光合金化掺杂自愈合材料 TiC 对热障涂层热腐蚀行为的影响具有重要意义。采用大气等离子喷涂技术（Atmospheric plasma spray，APS）在 Inconel 718 镍基高温合金表面制备 NiCrAlY 粘结层，采用大气等离子喷涂技术在 NiCrAlY 粘结层上制备 8 wt.%氧化钇部分稳定的氧化锆（8 wt.% yttria partially stabilized zirconia，8YSZ）陶瓷层，构建典型双层结构热障涂层体系。采用 1 kW 光纤耦合激光器将自愈合材料 TiC 熔于 8YSZ 热障涂表层，并考察其在 900 ℃下 25%NaCl+75%Na2SO4混合熔盐中保温 4 h 的热腐蚀行为。结果表明，与等离子喷涂涂层相比，激光合金化改性热障涂层表面更加光滑，分布有网状裂纹，且结构致密。等离子喷涂涂层的热腐蚀产物主要是针状颗粒 Y2(SO4)3 和 m-ZrO2，但仅有较少的热腐蚀盐渗透至激光合金化改性热障涂层内部，其热腐蚀产物为 Y2(SO4)3 和少量的 TiO2。激光合金化改性热障涂层的抗热腐蚀性能较等离子喷涂态热障涂层提升 55.5%，一方面激光合金化改性层组织致密，可阻止热腐蚀盐渗透至涂层内部，另一方面，激光合金化改性热障涂层表面粗糙度更低，能减少与热腐蚀盐的接触面积。此外，自愈合材料 TiC 在高温下发生氧化反应引起体积膨胀，实现裂纹的部分自愈合效应，进一步阻止了热腐蚀反应的发生。采用激光表面改性技术将自愈合材料 TiC 引入热障涂层，激光合金化改性热障涂层不仅具有光滑的表面形貌，还具有致密的微观组织结构；同时自愈合材料 TiC 在高温环境下的裂纹自愈合效应有助于抑制热腐蚀盐的渗透， 最终提高热障涂层的抗热腐蚀性能。
关键词:  等离子喷涂  激光合金化  热障涂层  抗热腐蚀性能  TiC  自愈合
DOI：10.11933/j.issn.1007-9289.20221209001
分类号:TG156；TB114
基金项目:国家自然科学基金青年基金（52105311）；浙江省“尖兵”“领雁”研发攻关计划（2023C01052, 2022C01117）；浙江省自然科学基金（LQ21E010002）资助项目
Effect of Laser Alloying TiC Doping on the Hot Corrosion Behavior of Plasma Sprayed 8YSZ Thermal Barrier Coatings
ZHANG Panpan1,2,3, SUN Yuhai1,2,3, SUN Lei1,2,3, LI Bo1,2,3, ZHANG Qunli1,2,3, YAO Jianhua1,2,3
1.School of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310023 , China;2.Institute of Laser Advanced Manufacturing, Zhejiang University of Technology, Hangzhou 310023 , China;3.Collaborative Innovation Center of High-end Laser Manufacturing Equipment,Zhejiang University of Technology, Hangzhou 310023 , China
Abstract:
Double-layered thermal barrier coatings (TBCs), which are composed of a top ceramic coating and a bonding coating, are widely used in the industry to reduce the surface working temperature of hot components. The primary materials used for the ceramic coating have been 6-8 wt.% Y2O3 partially stabilized ZrO2 (6-8YSZ), which has excellent performance of thermal insulation, high temperature resistance, low thermal conductivity, and effective thermal protection effect on metal substrates. However, traditional plasma-sprayed TBCs contain numerous pores and microcracks, and they are susceptible to corrosive salt penetration at high temperatures, leading to premature peeling failure. Doping with self-healing materials and laser post-treatment methods can effectively improve the hot corrosion resistance of TBCs. Therefore, this study aims to examine the effect of laser alloying on the hot corrosion behavior of plasma-sprayed TBCs. First, a NiCrAlY bonding coating is prepared on the surface of an Inconel 718 nickel-based superalloy via atmospheric plasma spray (APS) technology. An 8YSZ ceramic coating is then applied on the NiCrAlY bonding coating. Finally, self-healing TiC is melted on the plasma-sprayed 8YSZ coating by using a 1 kW fiber-coupled laser. The hot corrosion behaviors of the plasma-sprayed and laser-alloyed TBCs are investigated by immersion in 25% NaCl + 75% Na2SO4 mixed salt at 900 ℃ for 4 h. The weight losses of the plasma-sprayed and laser-alloyed TBCs following hot corrosion are examined. The microstructures of the plasma-sprayed and laser-alloyed TBCs before and after hot corrosion are studied using scanning electron microscopy. X-ray diffraction is used to characterize the phase composition of each coating, and energy-dispersive spectroscopy is used to analyze the elemental compositions. A high-precision electronic balance is used to measure the weights of the plasma-sprayed and laser-alloyed TBCs before and after hot corrosion, and the weight loss due to hot corrosion is determined. The results shows that the surface of the laser-alloyed TBCs is smoother. A few segmented microcracks are distributed on the laser-alloyed TBCs, which exhibits dense microstructure. The main corrosion products of the plasma-sprayed TBCs are needle-shaped Y2(SO4)3 particles and m-ZrO2. Meanwhile, only a small amount of corrosive salt penetrates the interior of the laser-alloyed TBCs, and its corrosion products are Y2(SO4)3 and a small amount of TiO2. After hot corrosion, the volume fraction of m-ZrO2 in the plasma-sprayed TBCs is 18.2%, whereas that in the laser-alloyed TBCs is only 8.1%. It is advisable to avoid the formation of m-ZrO2 during the preparation of 8YSZTBCs. If a detrimental phase transformation of t-ZrO2 to m-ZrO2 occurs, the original pores and cracks will serve as the starting points for stress relief, further exacerbating crack propagation and providing a pathway for the infiltration of corrosive salts, ultimately leading to coating delamination. On the one hand, the microstructure of the laser-alloyed TBCs is denser; this can prevent the penetration of corrosive salts into the interior of the coating. On the other hand, the surface roughness of laser-alloyed TBCs is lower, leading to lowered contact area with corrosive salts. Additionally, the self-healing material TiC undergoes an oxidation reaction during the hot corrosion test, resulting in partial self-healing of the pores and microcracks through volume expansion, further reducing the occurrence of hot corrosion reactions and the formation of harmful m-ZrO2 phases. Compared with plasma-sprayed TBCs, the laser-alloyed coatings shows an improvement in hot corrosion resistance by 55.5%.
Key words:  plasma spraying  laser alloying  thermal barrier coating  hot corrosion resistance  TiC  self-healing
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