Research On Integrated High Temperature Sensitive Film Materials And Temperature Sensors For Hot Components Of Aero-engine

The surface temperature and distribution of turbine blade and other hot components is one of the important input parameters for the design and development of aeroengines.Among various temperature measurement methods,thin-film thermocouple has the advantages of small mass,fast response and little interference to the measured environment,which is an advanced technology for accurately measuring the surface temperature and distribution of turbine blade and other hot components.In this dissertation,based on the accurate measurement of the surface temperature of the hot components of aero-engine,integrated sensitive film deposition,sensor design,preparation,performance calibration and application technology are systematically studied.The main research of this dissertation is as follows:1.Based on the multi-component alloy diffusion and high-temperature oxidation model,Matlab software was used to calculate the influence of temperature,film thickness,oxygen partial pressure and oxidation time on the diffusion and oxidation process,oxidation rate and grain size of Al element in Ni Cr Al Y film.The results show that when the heat treatment temperature is lower than 950°C,only Al elements from the surface of Ni Cr Al Y to the inner part of 9μm diffused to the film surface.When the heat treatment temperature rose to 1050°C,Al elements in the whole Ni Cr Al Y film were diffused to the surface of the film.In the oxidation temperature range of 950°C to 1050°C,the thermal growth Al₂O₃ on Ni Cr Al Y surface was composed of metastableθ,γphase Al₂O₃ andαphase Al₂O₃ at one atmosphere pressure.At 100 Pa,the thermal grown Al₂O₃ was a single steady-stateα-phase Al₂O₃.With the decrease of oxygen partial pressure,the oxidation rate of Al decreases.The grain size of Al₂O₃ increases with the increase of oxidation time.In the experiment,Ni₆₇Cr₂₂Al₁₀Y₁（wt.%）transition layer film was prepared by magnetron sputtering method on nickel-based superalloy substrates,and the vacuum aluminization and high temperature thermal oxidation treatment process were studied.Combined with the calculation results,optimized heat treatment process of Ni Cr Al Y film was obtained:Vacuum heat treatment temperature was 1050°C and time was 6 hours.The thermal oxidation temperature was 950°C,the oxygen partial pressure was 100 Pa,and the oxidation time was 12 hours.2.Al₂O₃ insulation layer of 2μm thickness and nanocrystalline-amorphous YSZ/Al₂O₃ composite insulation layer were prepared by reactive magnetron sputtering on the surface of thermal grown Al₂O₃.The fracture toughness and interface bonding strength of the samples were characterized by nano-indentation and nano-scratch.The results showed that:The Al₂O₃ insulation layer cracks at indentation depth of 200 nm and scratch depth of 4μm,but the YSZ/Al₂O₃ composite insulation layer does not crack at indentation depth of 800 nm and scratch depth of 6μm,indicating that the composite of nanocrystalline YSZ and amorphous Al₂O₃ can significantly improve the adhesion of Al₂O₃.The high temperature resistivity test results show that the insulation resistivity of YSZ/Al₂O₃ composite insulation layer is three orders of magnitude larger than that of Al₂O₃ insulation layer at 1000°C.The reason is that the activation energy of YSZ/Al₂O₃composite insulation layer is much less than that of Al₂O₃ insulation layer at high temperature.3.Based on the above research results,integrated Pt Rh/Pt thin film thermocouple was designed and prepared on turbine blade surface by magnetron sputtering and mask graphics.The sample of thin film thermocouple was composed of Ni Cr Al Y transition layer,thermal grown Al₂O₃ layer,YSZ/Al₂O₃ composite insulation layer and Pt and Pt Rh10 thin films.Ni Cr Al Y transition layer,thermally grown Al₂O₃ layer and YSZ/Al₂O₃composite insulation layer were all over the blade surface.Pt and Pt Rh10 films were graphic lines of 100 mm×1 mm×500 nm,with node width of 2 mm.The properties of thin-film thermocouple samples were calibrated by pulsed laser method and static calibration.The results show that the average response time of samples is 8.40μs.When the temperature ranges from 300°C to 900°C,the temperature measurement error is less than 1.4°C.4.Based on density functional theory,software such as VASP was used to calculate the effects of nitrogen doping and oxygen vacancy on the Gibbs free energy,bonding properties and thermoelectric properties of ITO film.The results show that the Gibbs free energy of ITO increases after nitrogen doping.At the same time,nitrogen doping causes the charge transfer of carrier to Sn-N bond,and causes the Sn-O bond of its nearest neighbor to produce an antibonding state.Therefore,the repair of oxygen vacancy in nitrogen-doped ITO requires higher activation energy.In addition,nitrogen doping introduces more impurity bands as valence band acceptors,which reduces the effective mass of electrons and carrier concentration,and the Seebeck coefficient is basically unchanged.Experimentally,ITO and nitrogen-doped ITO films were prepared by reactive magnetron sputtering.The microstructure,composition and compound state of the two groups of samples were characterized.The results showed that the lattice constant of ITO film increased after nitrogen doping,namely,the Gibbs free energy of the system increased.After high temperature vacuum annealing,the oxygen vacancy content of ITO film after nitrogen doping is higher,that is,nitrogen doping inhibits the repair of oxygen vacancy at high temperature,improves the stability of carrier concentration,and thus improves the thermoelectric stability and performance of ITO film.N doped ITO/Pt film thermocouple samples were prepared on superalloy substrate by reactive magnetron sputtering and mask graphics.The results show that the average response time of the samples is 16.67μs and the temperature error is less than 1.1°C in the temperature range of 100～1050°C.5.In order to adapt to the harsh environment of high temperature gas erosion,the YAl O/Si₃N₄/Al₂O₃ sandwich structure composite protective layer was designed and prepared on the surface of integrated Pt Rh/Pt film thermocouple,with the thickness of1.2μm,200nm,1.2μm,and the composite protective layer was annealed in nitrogen atmosphere at 1300°C.The results show that solid phase reaction occurs at the interface of YAl O/Si₃N₄ and Si₃N₄/Al₂O₃ at high temperature,the interface disappears,and dense composite films composed of YSi Al ON,Si Al ON and Al₂O₃ are formed.The drift rate of Pt Rh/Pt film thermocouple with composite protective layer is 2.19°C/h at 1350°C,while that of Pt Rh/Pt film thermocouple with single alumina protective layer is 13.27°C/h at1350°C.The experimental results prove that the composite protection layer of YAl O/Si₃N₄/Al₂O₃ sandwich structure can significantly improve the high temperature oxidation resistance of the integrated film thermocouple.6.Environmental assessment and verification tests were carried out on the prepared integrated film thermocouple.The cold effect test results show that the output thermoelectric potential of the Pt Rh/Pt integrated film thermocouple has a good following with the gas temperature during the continuous high temperature gas scour for 3 hours at the maximum total temperature of 800°C and the maximum total gas flow of 2.5 Kg/s.The test results of high-speed rotating parts show that the output thermoelectric potential of Pt Rh/Pt integrated film thermocouple samples has a good following with the ambient temperature at the maximum temperature of 200°C and the maximum speed of 14000rpm,and the output signal fluctuation of the sample is obviously lower than that of the sheathed thermocouple.The results of the high temperature combustion platform environmental test show that the N doped ITO/Pt integrated film thermocouple has not been found to be damaged after 6 hours of the combustion platform environmental test at the highest temperature of 1150°C and the maximum outlet static pressure of 1 MPa.