采用高温固相法合成了Nd2CexO3+2x(x=2.0,2.25,2.5,2.75,3.0)复合氧化物,在高温合金基体上采用等离子喷涂制备了该材料热障涂层。XRD分析结果表明Nd2CexO3+2x粉末和涂层均为立方萤石晶体结构。考察了CeO2含量对Nd2CexO3+2x的力学性能(弹性模量、维氏硬度和断裂韧性)和等离子喷涂涂层在1250℃抗热震性能的影响。随着CeO2含量增加,材料的弹性模量降低,维氏硬度和断裂韧性提高。通过提高初始粉末中CeO2的含量,获得了组成接近化学计量比Nd2Ce2O7的涂层,涂层的抗热震性能增强,热循环次数达到1000次以上。Nd2CexO3+2x涂层的失效原因主要是:与金属基体之间热膨胀系数不匹配、粘结层氧化和涂层烧结。
Abstract
Nd2CexO3+2x(x=2.0,2.25,2.5,2.75,3.0) composite oxides were prepared by solid-state reaction and their coatings were fabricated by atmospheric plasma-spraying on the superalloy substrates.The XRD results indicated that Nd2CexO3+2x and their coatings are crystallized in fluorite structure.The influence of CeO2 content on the mechanical properties,i.e.,Young’s modulus,Vickers hardness and fracture toughness of Nd2CexO3+2x,and the thermal shock behaviors of the plasma-sprayed Nd2CexO3+2x coatings at 1250℃ were systematically investigated.With the increase of CeO2 content,Young’s modulus of Nd2CexO3+2x decreases,while Vickers hardness and fracture toughness increase.Near-stoichiometric Nd2Ce2O7 coatings are achieved by the addition of excess CeO2 into the starting powders,therefore the thermal shock behaviors of Nd2CexO3+2x coatings are improved and the thermal cycling lives of the coatings exceed 1000 cycles.The failure of Nd2CexO3+2x coatings is believed to be induced predominantly by the thermal expansion mismatch stress between the ceramic top coat and the substrate/bond coat,oxidation of bond coat and sintering of the ceramic top coat.
关键词
热障涂层 /
复合氧化物 /
力学性能 /
抗热震性能 /
二氧化铈
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Key words
Thermal barrier coat /
Composite oxide /
Mechanical propertie /
Thermal shock behavi /
Ceria
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脚注
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基金
国家自然科学基金资助项目(50825204)
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