| With the rapid development of modern science and technology,the design and operation indexes of aerospace engines,nuclear industrial equipment,turbines,internal combustion engines and other industrial equipment have also been continuously improved.Comprehensive external factors such as high centrifugal force,airflow impact,high temperature and strong vibration will act on the working turbine blades at the same time.Therefore,it is necessary to obtain the stress distribution state and strain information of key components of the engine to ensure the long-term and reliable normal operation of the engine.It is of great significance to develop a reliable and high-precision strain measurement sensor and develop high-temperature strain measurement technology to realize real-time monitoring of surface strain information of components in high-temperature environment.The thin film strain gauge prepared by vacuum coating has outstanding advantages in thickness control,response speed and measurement accuracy.At the same time,without additional bonding and fixation,it will not damage the equipment structure,and has little impact on the mechanical properties.Based on this,the thin film strain gauge is prepared by vacuum coating technology in this paper.This paper presents an Al2O3/Ce O2/Al2O3 composite insulation layer which can be used for high temperature insulation up to 900℃.For the optimization of the preparation process of single layer thin film in the composite structure,focusing on the effects of gas flow ratio,sputtering temperature and annealing treatment on the properties of the insulation layer thin film.Then compare the properties of composite insulation layers with different thickness structures.Finally,the Al2O3/Ce O2/Al2O3composite insulation layer is prepared by the optimized process.Finally high temperature film strain gauges are prepared and their strain properties at high temperatures are tested.The main research contents are as follows:1.Al2O3 thin films were prepared on nickel base alloy substrates by DC magnetron reactive sputtering.The effects of argon oxygen flow ratio on the microstructure and high temperature insulation properties of Al2O3 thin films were studied.The optimized argon oxygen flow ratio was 50:2.5;Ce O2 thin films were prepared on nickel base alloy substrate and silicon wafer by DC magnetron reactive sputtering.By controlling the experimental process parameters,the effects of gas flow ratio,sputtering temperature and annealing treatment on the microstructure and high temperature insulation properties of Ce O2 thin films were analyzed and studied.The optimized process was argon oxygen gas flow ratio of 30:5,sputtering temperature of 200℃,900℃annealing for 2h.The final optimized Al2O3/Ce O2/Al2O3 composite insulation layer is 0.75μm Al2O3/1.5μm Ce O2/0.75μm Al2O3,the insulation resistance is 1.9 MΩat 900℃,and the high temperature insulation performance is excellent.2.NiCrAlY transition layer,thermally grown oxide layer,Al2O3/Ce O2/Al2O3composite structure insulating layer,pdcr strain functional layer and high temperature protective layer are successively prepared on nickel base superalloy samples by DC magnetron sputtering and aluminum precipitation oxidation.Finally,the signal lead connection is completed to prepare high temperature thin film strain gauge with the size of 7.48 mm×4.7 mm.3.Performance test of thin film strain gauge:cold and hot shock results show that it has high temperature reliability;The static calibration test shows that the average resistance coefficient from room temperature to 900℃is 738.69ppm/℃,and the resistance drift rate is 0.43%/h.It works normally from room temperature to 800℃,and the maximum test strain exceeds 370με,The GF of room temperature,400℃,600℃and 800℃are 1.73,2.1,2.87 and 3.18 respectively.The GF of thin film strain gauge increases with the increase of temperature.. |
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