Research On Fabracation And Properties Of Strain Gauges Integrated With Turbine Blade

Aero-engine turbine blades need to withstand the effects of high temperature,high pressure,high eccentricity,thermal stress,and severe vibration while the engine is running.In this extreme environment,with the accumulation of time,the blades are prone to damage and failure,and then cause a malfunction to the engine.Therefore,in order to reduce safety accidents caused by faults,it is necessary to accurately and timely monitor the strain caused by the vibration of high-temperature components such as turbine engine blades in condition of working.In this paper,the DC magnetron sputtering method and the electron beam evaporation method are used to prepare a multi-layer structure/function integrated PdCr high temperature thin film strain sensor on a Ni-based superalloy substrate.The data measured by this strain gauge is highly accurate,reliable and has a higher sensitivity coefficient and faster response time,which is easy to integrate and resists high pressure,high temperature and air flow,so it can meet the requirements of strain testing under extreme conditions.This paper mainly develops an insulating layer with good insulation at 1000℃,and studies the influence of film deposition process and annealing on its microstructure and insulation performance.Based on the CeO₂ thin film insulating layer prepared under the optimized process,the multi-layer structure of PdCr high-temperature thin film strain gauge was made,and then the strain performance at high temperature was tested.The main contents and conclusions are as follows:1.The CeO₂ film was prepared on Ni-based superalloy substrate and Al₂O₃ ceramic substrate by electron beam evaporation method.In this paper,the influence of substrate temperature,film thickness and annealing treatment on the microstructure and insulation properties of CeO₂ film was studied as well.The optimized process parameters obtained are:background vacuum 5′10^-4 Pa,evaporation rate 0.5nm/s,substrate temperature300℃,deposition time 34min,deposition thickness 1μm,and then annealed it under 1000℃for 4 times,the resistance of sample is around 3.2MΩ.Eventually,the thermal fatigue test and thermal shock test were carried out to verify its high temperature stability.2.The multilayer PdCr thin film strain gauge consisting of Ni Cr Al Y transition layer,CeO₂ insulating layer,PdCr functional layer and CeO₂ protective layer was prepared on the Ni-base superalloy substrate.The aluminum evolution oxidation process of the transition layer was optimized,and the density and stability of the thermal growth oxide layer were improved.The resistance temperature coefficient（TCR）is 316 ppm/℃,and the strain sensitivity coefficient（GF）is 3.34 at 800℃.