摘要
优异的抗熔融V_(2)O_(5)+Na_(2)SO_(4)腐蚀能力是热障涂层面层材料选择的关键性能指标。通过Gd掺杂实现了1250℃下La_(2)(Zr_(0.7)Ce_(0.3))_(2)O_(7)陶瓷材料抗熔融V_(2)O_(5)+Na_(2)SO_(4)腐蚀性能的提升,采用固相反应法制备了(La_(1-x)Gd_(x))_(2)(Zr_(0.7)Ce_(0.3))_(2)O_(7)(x=0、0.5)陶瓷材料,并评估了其在900~1250℃的抗熔融V_(2)O_(5)+Na_(2)SO_(4)腐蚀性能。结果表明:Gd_(2)O_(3)掺杂后La_(2)(Zr_(0.7)Ce_(0.3))_(2)O_(7)陶瓷材料各温度腐蚀深度分别下降约24%、16%、7%、7%,表现出优异的抗腐蚀性能。(La_(0.5)Gd_(0.5))_(2)(Zr_(0.7)Ce_(0.3))_(2)O_(7)陶瓷材料优异的抗V_(2)O_(5)+Na_(2)SO_(4)腐蚀性能主要归因于晶格畸变增加引起的缓慢扩散及化学碱性的协同作用。
Introduction One of the major reasons for the failure of thermal barrier coating materials is the corrosion caused by the reaction between aeroengine thermal barrier coating materials(TBC)and V_(2)O_(5)+Na_(2)SO_(4)in fuel under high-temperature service conditions.Conventional TBCs are difficult to meet the increasingly harsh high-temperature service environment.It is thus necessary to develop new and more corrosion-resistant thermal barrier coating materials.Among the materials to replace conventional TBC,La_(2)(Zr_(0.7)Ce_(0.3))_(2)O_(7)(LZC)ceramics are considered as potential TBC candidates due to their high sintering resistance,low thermal conductivity and high thermal expansion coefficient.Also,the thermal conductivity of LZC can be effectively reduced by using Re^(3+)with large mass and small radius doping at La^(3+).Therefore,the modified(La_(0.5)Gd_(0.5))_(2)(Zr_(0.7)Ce_(0.3))_(2)O_(7)(LGZC)doped with Gd^(3+),which is a rare-earth element and has a smaller ionic radius,can further reduce the thermal conductivity of the material and improve the mechanical properties of the material through fine-grain strengthening.However,the existing reports on the hot corrosion resistance of V_(2)O_(5)+Na_(2)SO_(4)molten salt of LZC and LGZC materials are more limited to the strong corrosive properties at<1050℃,while the actual service temperature of the coating often exceeds 1200℃.Methods In this work,ZrO_(2),La_(2)O_(3),Gd_(2)O_(3),CeO_(2) and other oxide powders were used as raw materials,and LZC and LGZC ceramic samples were prepared by a high-temperature solid-state reaction method.A typical mixed salt of V_(2)O_(5)+Na_(2)SO_(4)(in a molar ratio of 1:1)was used as a corrosive medium.V_(2)O_(5) and Na_(2)SO_(4) powders were mixed.The mixed powder was evenly spread on the surface of the ceramic sample at a concentration of 10 mg/cm^(2),and then the coated ceramic sample was placed in a box-type resistance box and treated at 900,1000,1100 and 1250℃for 5 h for thermal corrosion,respectively.The phase composition of LZC and LGZC samples before and after hot corrosion was determined by a model D8 X-ray diffractometer(XRD,Bruker Co.,Germany).The microstructure and morphology were characterized by a model Sigma 500scanning electron microscope(SEM,ZEISS Co.,Germany)equipped with energy dispersive spectrometer(EDS).Results and discussion LZC and LGZC ceramic specimens with a single pyrochlorite structure were synthesized.After corrosion,the diffraction peak of LGZC reduces,compared to that of LZC ceramic samples.There are mainly(La,Ce,Gd)VO_(4),t-ZrO_(2) and m-ZrO_(2) on the surface according to the SEM images and EDS results.The content of(La,Ce,Gd)VO_(4) increases with the increase of temperature in the range of 900-1100℃,and decreases after corrosion at 1250℃.From the micromorphology after corrosion,the ceramic surface of LZC specimens after corrosion at 900-1100℃is mainly rod-like grains and granular clusters,while LGZC has more rod-like grains rather than granular grains.After corrosion at 1250℃,the surface of the LGZC specimen is granular crystals with intracrystalline pores.LZC and LGZC both forman obvious corrosion layer at 900-1100℃,and the thickness of the corrosion layer increases with the increase of temperature,and the corrosion layer becomes the thickest at 1100℃(i.e.,38μm and 35μm),respectively.However,after corrosion at 1250℃,the corrosion layer does not form and the corrosion depth decreases,and the darker molten salt penetrates further downward,showing two completely different microscopic morphologies.Also,the corrosion depth of LGZC is smaller than that of LZC at different temperatures.Conclusions LZC and LGZC ceramic materials reacted with V_(2)O_(5)+Na_(2)SO_(4)at 900-1100℃to form a relatively dense corrosion reaction layer,and the corrosion reaction degree increased with the increase of temperature,and the reaction was most intense at 1100℃.The hot corrosion mechanism of LZC and LGZC ceramic materials at 900-1250℃followed Lewis’s acid-base law and Gibbs's free energy.The relative alkalinity of LGZC decreased,and the corrosion depth of LGZC was smaller than that of LZC at different temperatures due to the doping of Gd_(2)O_(3).The corrosion resistance of ceramic materials was reflected in the corrosion depth,the smaller the corrosion depth,the stronger the corrosion resistance of the ceramic materials.Therefore,LGZC was more resistant to V_(2)O_(5)+Na_(2)SO_(4)corrosion than LZC in this case.After the temperature increased to 1250℃,neither of the two samples formed a dense corrosion reaction layer,and the corrosion depth was smaller than that after corrosion at 1100℃because the viscosity of NaVO_(3) decreased with the increase of the corrosion temperature to 1250℃and blocked the pores in a short time,thus preventing a further penetration of the molten salt.
作者
曲肖夫
谢敏
宋晓炜
张永和
宋希文
王志刚
QU Xiaofu;XIE Min;SONG Xiaowei;ZHANG Yonghe;SONG Xiwen;WANG Zhigang(School of Materials Science and Engineering,Inner Mongolia University of Science and Technology,Baotou 014010,Nei Mongol,China;Inner Mongolia Key Laboratory of Advanced Ceramic Material and Devices,Baotou 014010,Nei Mongol,China;KeyLaboratory of Green Extraction&Efficient Utilization of Light Rare-Earth Resources,Ministry of Education,Baotou 014010,Nei Mongol,China)
出处
《硅酸盐学报》
北大核心
2025年第3期620-629,共10页
Journal of The Chinese Ceramic Society
基金
国家自然科学基金项目(52372062,52462011)
内蒙古自治区高等学校青年科技人才发展项目(NJYT23008)
内蒙古自治区高等学校科学研究项目(NJZZ23055)
北方稀土科研项目(BFXT-2022-D-0053)
内蒙古自然科学基金项目(2024MS05021)
内蒙古教育厅一流学科科研专项项目(YLXKZX-NKD-033)。
关键词
热障涂层材料
锆酸镧基陶瓷材料
熔融盐腐蚀
五氧化二钒
硫酸钠
thermal barrier coating materials
lanthanum-based zirconate ceramic materials
molten salt corrosion
divanadium pentaoxide
sodium sulfate
