陈旭,方帅帅,李成新,李长久.等离子喷涂钛酸锶镧 / 金属复合涂层组织结构及性能的研究[J].热喷涂技术,2021,13(2):1~9.
等离子喷涂钛酸锶镧 / 金属复合涂层组织结构及性能的研究
Microstructure and Properties of Plasma-Sprayed Lanthanum-DopedStrontium Titanate/Metal Composite Coatings
  
DOI:10.3969/j.issn.1674-7127.2021.02.001
中文关键词:  喷涂参数  NiCrCuB 涂层  成分  微观组织  力学性能  氧化机制
英文关键词:Spray parameters  NiCrCu coating  Composition  Microstructure  Mechanical property  Oxidation mechanism
基金项目:
           
作者单位
陈旭 西安交通大学 材料科学与工程学院金属材料强度国家重点实验室
方帅帅 西安交通大学 材料科学与工程学院金属材料强度国家重点实验室
李成新 西安交通大学 材料科学与工程学院金属材料强度国家重点实验室
李长久 西安交通大学 材料科学与工程学院金属材料强度国家重点实验室
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中文摘要:
      钛酸锶镧 (LST) 作为一种新型固体氧化物燃料电池 (SOFC) 连接体材料, 其导电性能远低于金属连接体, 且受制备条件影响显著。 本研究分别将不同体积分数的 Ni、 Fe 及 SS430 不锈钢粉末与 LST 混合, 通过大气等离 子喷涂技术制备了相应的复合连接体涂层, 并系统研究了材料组合对其组织结构、 导电性能及稳定性的影响。 研 究结果表明, LST/Ni 复合连接体涂层随着金属体积分数的增大, 其导电率显著提高, 达到甚至远超过 LST 烧结 块体的水平; 同时, 由于热膨胀匹配的问题, 过高的 Ni 比例使得复合涂层在经受热循环后发生明显的纵向开裂, 显著降低其气密性。 由于Fe颗粒在喷涂过程中的严重氧化, LST/Fe复合连接体涂层的导电性能没有得到明显改善。 10% 体积分数 SS430 混合喷涂粉末制备的 LST/SS430 复合涂层, 具有高电导率和热稳定性, 满足高性能 SOFC 连接体的要求。 粉末, 以期通过 B 在高温熔滴飞行中的牺牲氧化并蒸发去除氧化物机制, 在大气等离子喷涂条件下获得无氧化 物的熔滴制备高致密的金属涂层。 为此, 采用粒度 30~50 μm 的 NiCrCu1.5B 和 NiCrCu4B 喷涂粉末, 研究了粉末 成分与大气等离子喷涂工艺参数对涂层成分、 组织结构及力学性能的影响。 结果表明, 等离子喷涂制备 NiCrCuB 涂层时, 基体在等离子射流
英文摘要:
      As a novel material of bi-layer interconnect for solid oxide fuel cells (SOFC), La-doped SrTiO3 (LST) is usually sintered in a reducing atmosphere at a high temperature of above 1400℃ to achieve high conductivity and gas-tightness. Such high temperature sintering will lead to the formation of low conductive phases and non-active phases at the interfaces between functional layers in SOFC cells. Using atmospheric plasma spraying (APS) to deposit the LST interconnect can avoid the above adverse effect. By increasing the deposition temperature, dense LST coating with enhanced inter-lamellar bonding can be prepared by APS. However, the electrical conductivity of LST coating at 850℃ is only half the value of sintered LST bulk, which is several orders of magnitude lower than that of metallic interconnect. To improve the conductivity of the interconnect, LST/Ni, LST/Fe, and LST/SS430 composite interconnects are designed. The interconnects were deposited by APS using the powder blend with mixing the dense LST powders of 30~60 μm with metallic powders of 10~50 μm with different metal proportions in this study. APS was performed with the substrates preheating to ~450℃ using Ar-H2 plasma jet at a plasma arc power of 42 kW. The effects of metal material types and contents on the microstructure, conductivity and stability of the composite coatings were investigated. The microstructure of the composite interconnects was examined by scanning electron microscopy and the crystalline structure of the interconnects were characterized by X-ray diffraction. The conductivity of the composite coatings was measured by the standard DC four-probe method in an anode atmosphere (97% H2/3% H2O). The gas-tightness of the composite coatings was evaluated by gas permeability measurements. The stability of the interconnect was also examined by subjecting the interconnect to the repeated thermal cycles. The results show that by adding 5 vol.% Ni in the feedstock powder, the electrical conductivity of dense LST/ Ni interconnect coating is ~187 S/cm at 850℃ , which is comparable to that of sintered LST bulk. The conductivity of the composite coatings is significantly increased with the increasing proportion of Ni. However, due to the thermal mismatch between LST and Ni lamellae, cracking in the direction along the coating thickness occurs during thermal cycles for the composite coating with an excessively high proportion of Ni, which would significantly decrease the gas-tightness of the coating. The conductivity of LST/Fe composite coating was not remarkably improved because of the serious oxidation of Fe particles during the spray process. The electron transport across the metal constituent was blocked by the iron oxide scales. On the other hand, by adding 10 vol.% SS430 to the LST feedstock powder, the dense LST/SS430 interconnect coating was deposited by APS. The LST/SS430 interconnect exhibits a high electrical conductivity of ~300 S/cm at 850℃ and favorable stability against thermal cycles. The results illustrate that the optimized composite interconnect by APS fulfills the requirement of SOFC interconnect with high performance.
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