Abstract—

The aim of the study was to create a technique for calculating the thermal conductivity of a thin surface layer or coating, which differs significantly from the base metal in structure, phase composition, and thermal properties. The technique is based on the experimental measurement of the contact potential difference (CPD) at the layer/coating–substrate interface, followed by the calculation of the electron work function and the energy of the Fermi level. Distinctive features of the developed methodological apparatus are the characteristics of the microstructure, phase composition, and porosity of the layer/coating, which are taken into account in the calculation model and significantly affect the final result of determining the effective thermal conductivity. The calculation and experimental approbation of the idea was implemented in the process of studying the blades of an experimental gas turbine locomotive engine with a heterophase thermal barrier coating of the Nb–Ti–Al system. The material of the blades is Inconel 713LC cast chromium–nickel superalloy. Coatings with a thickness of about 80 µm were deposited using the vacuum ion-plasma technology. During the development of the methodology for calculating the thermal conductivity, the experimental data of the CPD were obtained by instrumental measurements according to a specially developed laboratory procedure. Data on the morphology of the structure of coatings, their phase composition, and porosity were studied by traditional metal-physical methods and integrated into the calculation part of the technique. The results of model calculations of the thermal conductivity of both the base metal of the substrate (turbine blades) Inconel 713LC and the Nb–Ti–Al thermal barrier coating showed a high agreement with experimental and reference data. The technology has a high potential for application in heavily loaded friction units in various areas of the national economy, such as helicopter construction, aircraft construction, aerospace, railway transport, shipbuilding, and defense.

中文翻译：

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重载摩擦系统中异相表面层、涂层和薄膜的有效热导率的分析测定

摘要—

该研究的目的是创建一种计算薄表面层或涂层的导热系数的技术，该薄表面层或涂层在结构、相组成和热性能方面与基本金属有显着差异。该技术基于层/涂层-基板界面接触电势差 (CPD) 的实验测量，然后计算电子功函数和费米能级的能量。开发的方法设备的显着特征是层/涂层的微观结构、相组成和孔隙率的特征，这些特征在计算模型中被考虑在内，并显着影响确定有效导热系数的最终结果。该想法的计算和实验验证是在研究带有 Nb-Ti-Al 体系异相热障涂层的实验性燃气轮机机车发动机叶片的过程中实现的。叶片材料为 Inconel 713LC 铸造铬镍高温合金。使用真空离子等离子体技术沉积了厚度约为 80 µm 的涂层。在计算热导率的方法开发过程中，CPD 的实验数据是根据专门开发的实验室程序通过仪器测量获得的。通过传统的金属物理方法研究了涂层结构形态、相组成和孔隙率的数据，并将其整合到该技术的计算部分。基底金属（涡轮叶片）Inconel 713LC 和 Nb-Ti-Al 热障涂层的热导率模型计算结果与实验和参考数据高度一致。该技术在直升机制造、飞机制造、航空航天、铁路运输、造船、国防等国民经济各个领域的重载摩擦装置上具有很大的应用潜力。