Thick Graded Nanostructured Zirconia-NiCoCrAlY Composite Coatings by Plasma Spraying

Thick Nanostructured PSZ-NiCoCrAlY graded TBCs were got byair plasma spraying. The results reveal the morphology and phase transformation of TBCs by means of SEM and XRD. The plasma spray process results in a characteristic layered structure consisting of lamellae, unmelted nano-particles and an inter-lamellar porosity. The test results of thermal shock show that the graded coatings have different failure behavior. The failure mode was the spallation of top coat due to thermal stress. It has been found that the lamella consists of nanoscale columnar grains parallel to the spraying direction.     

超音速等离子喷涂制备梯度功能热障涂层的特点

在国内最新研制成功的超音速等离子喷涂系统基础上,开发了国内外独创的“双通道、双温区”超音速等离子喷涂工艺,将高熔点陶瓷粉末和低熔点合金粉末分别送入等离子焰流的不同温度区,保证两种粉末分别达到各自的熔点,再均匀混合后以超音速喷射到基体形成涂层,克服了传统的“金属/陶瓷混合法”制备梯度热障涂层时,低熔点金属相过熔而引起的氧化、脆化问题。制备出的Ce-YSZ/NiCoCrAlY梯度功能热障涂层(FG-TBCs)组织结构均匀致密,陶瓷与金属组份呈连续梯度分布,显示出良好的韧性。在自行开发的多功能旋转式热震试验机上对约1 mm厚的涂层经1 200℃加热、淬水,200周次热震试验后,涂层表面仅出现了细微网状裂纹,裂纹垂直向下扩展最深350μm,止于梯度层中塑性金属区,未发现任何涂层剥落现象。     

Dominant effect of particle size on the CeO2 preferential evaporation during plasma spraying of La2Ce2O7

The inhomogeneous composition distribution of atmospheric plasma sprayed La₂Ce₂O₇ limits its operation in thermal barrier coatings. Two types of La₂Ce₂O₇ powders were used to investigate the effect of the powder size and structure on the preferential evaporation of Ce during plasma spraying. The results indicate that powder particle size is dominant for the Ce evaporation loss. Such effect is significantly intensified with the decrease of particle size. When the particle size is larger than 30 μm, the Ce loss is less or can be neglected. Two mechanisms including the element diffusion mechanism and convection mass transfer mechanism are proposed to well explain the evaporation rule. Moreover, the loss of Ce is higher using the agglomerate-sintered powder due to its higher thermal conductivity than the as-agglomerated powder. Correspondingly, the CeO₂ loss can be neglected in the coatings as the agglomerated powders with a size <30 μm were used.     

热喷涂复合结构MCrAlY/8YSZ热障涂层的抗剥落能力

在陶瓷涂层与金属粘接层之间制备一层NiCoCrAlTaY/YSZ复合过渡层和通过半熔化团聚YSZ粉末制备层状/多孔团状复合结构YSZ隔热层,用SEM表征了涂层的显微组织;依照ASTM C633标准测试了涂层的结合强度;用压痕法测试了陶瓷层的弹性模量和断裂韧性。用激光脉冲法测试了陶瓷层的热导率。用高温水淬快速冷却实验验证涂层的抗剥落性能。结果表明,在不降低涂层隔热效果的前提下复合过渡层和和隔热层显著提高了涂层的抗剥落能力。HVOF制备的NiCoCrAlTaY粘接层组织致密,没有明显的氧化物;APS制备的NiCoCrAlTaY/YSZ复合过渡层内层间的结合良好,组织致密,金属与陶瓷粒子呈现出典型的层状交替分布特征;陶瓷层由典型层状结构内包含约11%未完全熔化团聚粉末形成的弥散分布多孔团状组织构成。复合结构使等离子喷涂TBC的结合强度由25.8 MPa提高到38.6 MPa,陶瓷层的弹性模量和热导率没有明显的变化,但是断裂韧性提高了1倍以上,涂层出现30%剥落的平均水淬周次由19.7次提高到72.1次,表明抗剥落能力显著提高。     

稀土掺杂ZrO_2基热障涂层陶瓷材料研究进展

热障涂层用于燃气轮机的热端部件,不仅可以显著提高其使用温度,延长热端部件的使用寿命,而且提高了燃气轮机发动机的效率.介绍了稀土掺杂ZrO2基热障涂层的研究现状及发展趋势.结果表明LnO1.5-Ta2O5（或Nb2O5）-YSZ材料既可以提高传统YSZ热障涂层的使用温度,而且也降低了其热导率.LnO1.5-Ta2O5（或Nb2O5）-YSZ材料可以作为热障涂层系统中陶瓷顶层的下一代候选材料.     

热喷涂纳米结构热障涂层的最新研究

分析列举了近些年来热喷涂纳米结构热障涂层（TBCs）的最新研究进展和成果。重点比较了热喷涂纳米结构TBCs与传统TBCs之间的性能差异。最后对热喷涂TBCs的研究前景作了展望。     

Phase structure and thermal conductivities of Er2O3 stabilized ZrO2 toughened Gd2Zr2O7 ceramics for thermal barrier coatings

3.5 mol% Er₂O₃ stabilized ZrO₂ (ErSZ) and Gd₂Zr₂O₇ powders were produced by a chemical co-precipitation and calcination method, and ErSZ was used to toughen Gd₂Zr₂O₇. The phase structure, toughness and thermal conductivities of ErSZ toughened Gd₂Zr₂O₇ ceramics were investigated. When the ErSZ content was below 15 mol%, the compound consisted of pyrochlore phase, the ordering degree of which decreased with the increase of the ErSZ content. High ErSZ doping led to the formation of metastable tetragonal (t′) phase in the compound. The addition of ErSZ in Gd₂Zr₂O₇ benefited its toughness, mainly attributable to the presence of t′ phase in the compound. With the increase of the ErSZ content in the compound, the thermal conductivity first decreased and then showed an upward tendency, and 10 mol% ErSZ toughened Gd₂Zr₂O₇ exhibited the lowest thermal conductivity.     

等离子喷涂ZrO2热障涂层热冲击破坏研究

对比研究了等离子喷涂ZrO2梯度热障涂层及传统的双层结构热障涂层,选择NiCoCrAlTaY合金粉末作为热障涂层的粘结底层材料、7％Y2O3-ZrO2作为热障涂层的面层材料、不同比例的NiCoCrAlTaY与7％Y2O3-ZrO2(YPZ)复合粉末作为梯度过渡层材料,然后进行热冲击试验、金相分析及扫描电子显微镜形貌分析,结果表明梯度热障涂层热冲击寿命明显高于传统的双层结构热障涂层。     

High temperature properties of thermal barrier coatings obtained by detonation spraying

NiCrAlY/YPSZ and NiCrAlY/NiAl/YPSZ thermal barrier coatings (TBCs) were successfully deposited by detonation spraying. The results indicated that the detonation sprayed TBCs included a uniform ceramic coat containing a few microcracks and a bond coat with a rough surface. The lamellar structure and the presence of cracks and impurities could reduce the thermal conductivity of the ceramic coat. Oxidation kinetics at 1000–1150 °C of detonation sprayed TBCs have been measured and discussed. The role of a Ni–Al intermediate layer in improving the oxidation resistance of duplex TBCs has also been studied.     

热障涂层用YxGa3-xAl5O12陶瓷的固相合成及其机理研究

以Y2O3、Gd2O3和Al2O3为原料，利用固相合成法在1600℃下合成了具有石榴石结构的YxGd1-xAl5O12材料，其中x=1，1．5，2，3。采用XRD对合成产物的物相组成以及合成机理进行了分析表征。结果表明：合成产物的晶面间距随X值的增大而减小，在固相合成反应过程中生成了中间相Y4Al2O9和GdAlO3。