用中子散射和图像分析技术研究悬浮热喷涂YSZ热障涂层孔隙率的变化
Evolution of Porosity in Suspension Thermal Sprayed YSZ Thermal Barrier Coatings through Neutron Scattering and Image Analysis Techniques
摘要：
孔隙率是热障涂层的一个关键参数，直接影响涂层的热导率和应变容限。悬浮高速氧燃料（SHVOF）热喷涂使得能够使用亚微米颗粒作为原料，增加对孔隙率的控制并引入纳米尺寸的孔;这些精细尺度的孔隙率具有挑战性。中子散射是一种非破坏性的技术，由于小角（SANS）和超小角中子散射（USANS）技术的结合，能够研究孔径范围为1 nm至10 um的孔隙度。数字图像上的图像分析（IA）允许研究尺寸大于~100 nm的孔隙度。在这项工作中，两个氧化钇稳定的氧化锆（ZrO 2与8 wt.% Y2 O3）悬浮液进行喷雾，并在1100、1200、1300和1400 °C下热处理72小时。首次在SHVOF 8 YSZ中，使用SANS & USANS和IA研究了孔径分布、总孔隙率和孔形态，以确定热处理的影响。通过X射线衍射和显微硬度测试研究了涂层中的相变过程及其对涂层力学性能的影响。结果表明，喷涂涂层中存在大量的纳米孔，在1100 °C热处理过程中，纳米孔消失;在1200 °C下，从初始亚稳的四方相到四方相和立方相的相变导致了从层间片状孔到球状孔的转变，以及微裂纹的出现和微应变的积累。相变在1400 °C时完成，没有单斜相的存在
英文摘要：
Porosity is a key parameter on thermal barrier coatings, directly influencing thermal conductivity and strain tolerance. Suspension high velocity oxy-fuel (SHVOF) thermal spraying enables the use of sub-micron particles as feedstock, increasing control over porosity and introducing nano-sized pores; these fine-scale porosities being challenging to measure. Neutron scattering represents a non-destructive technique, capable of studying porosity with a pore size range of 1 nm to 10 um, thanks to the combination of small-angle (SANS) and ultra-small-angle neutron scattering (USANS) techniques. Image Analysis (IA) on digital images allows for the study of porosity with a size above ~100 nm. In this work, two yttria-stabilised zirconia (ZrO2 with 8 wt.% Y2O3) suspensions were sprayed and heat treated at 1100, 1200, 1300 and 1400 °C for 72 h. For the first time in SHVOF 8YSZ, pore size distribution, total porosity and pore morphology were studied using SANS & USANS and IA to determine the effects of heat treatment. X-ray diffraction and micro-hardness measurements were performed to study the phase transformation, and its effects on the mechanical properties of the coating. The results show an abundant presence of nano-pores in the as-sprayed coatings, which are eliminated during heat treatment at 1100 °C; a transition from inter-splat lamellar pores to globular pores and the appearance of micro-cracks along with the accumulation of micro-strains associated with the phase transformation from the initial metastable tetragonal into tetragonal and cubic phases at 1200 °C. The phase transformation was completed at 1400 °C, with no presence of monoclinic phase
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