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Thermal barrier coatings (TBCs) is one of the main key technology for the high-pressure turbine blades which are the main components of the high-performance aerospace engines. It offers protection for underline metallic components from corrosion, oxidation and localized melting by insulating the metal from hot gases in the engine core. The properties and lifetime of TBCs are greatly influenced by the preparation technology, which includes plasma spraying (PS), physical vapor deposition (PVD) and laser re-melting (LM). In this paper, three technologies used to prepare the TBCs are reviewed. Resulting features of coating fabricated by each technology are also discussed such as: the porosity, the thermally grown oxide (TGO), the erosion resistance, the thermal shock and so on. Especially, it is pointed out that the performances of gradient coating and nano-coating are better than the traditional coatings. In addition, it is widely accepted that laser can be applied to re-melt the PS coating and even directly clad the gradient coating. In the future, the traditional preparation technology should be improved continually in order to enhance the coating lifetime, enhance the properties of coating and lower the cost of process. Moreover, the researches on gradient-nano-structured coatings preparation are absent and should be done with emphasis since the nano-structure and gradient structure can both benefit the lifetime and properties of coatings.

The accurate measurement of axial stress of bolts is an essential means to ensure the stable operation of an aero-engine. In the measurement of axial stress of bolt by ultrasonic method, the change of ultrasonic velocity caused by stress is not obvious. In order to ensure the accuracy of ultrasonic velocity measurement, it is necessary to measure the difference of ultrasonic propagation time accurately. A high-sampling rate signal is the prerequisite to improve the measurement accuracy of the ultrasonic propagation time difference. In this paper, by studying the characteristics of ultrasonic signals, sine function interpolation is used to improve the time resolution. The experimental results show that after the sine function interpolation is performed on the ultrasonic signal recorded at a sampling rate of 100 MHz, the average error of bolt axial stress measurement is reduced by 4.288 MPa. Therefore, the sine function interpolation method of ultrasonic signals proposed in this paper can effectively improve the measurement accuracy of the propagation time difference, thereby reducing the measurement error of the bolt axial stress in the large-scale high-speed rotating equipment represented by aero-engines.