Fabrication Of TaN Thin Film Strain Gauges For Strain Measurenment Of Turbine Blades

When the aircraft engine is in operation, the blades which are withstanding the comprehensive function of high centrifugal force, thermal stresses, high vibration and high temperature are prone to failure. Therefore, it is critical and necessary to test the vibration of blades in the study of aircraft engine. The thin film strain gauges which are integrated by function and structure are deposited on the surface of blade directly use the film technology. The thickness of strain gauges is in micrometer magnitude. The film stain gauges possess advantages of small disturbance to the engine, no breaking of the mechanical structure of blade, rapid response, high sensitivity and high resistant of high temperature, high pressure, flow erosion, etc.In order to find the best preparation conditons for TaN thin film strain gague, the TaN film strain gauges are deposited on the surface of Al2O3 ceramic substrate by intermediate frequency reactive magneto sputtering and we the effect of the process parameters which are sputtering temperature, sputtering pressure, vacuum annealing time for the microstructure of TaN thin films and the strain sensitive characteristics were studied. The best preparation conditions are: 200 W of sputtering power, 60 min of deposition time, 1μm of the film thickenss, 200 sccm of Ar gas flow and 8 sccm of N2 gas flow, 4% of N2/Ar gas flow ratio, 0.6 Pa of sputtering pressure, 800 ℃ of vacuum annealing temperature and 4 h of holding time. The film strain gauges performances of the strain gauges prepared by optimized preparation technology are 2 of GF,-69.76 ppm/℃of TCR.Secondly, in view of the TaN strain gauges easily oxidized at high temperature and the disadvantage of poor repeatability, this paper studied the different thickness ratio of TaN/Pd Cr double film preparation process of strain gauge and strain sensitive features. Results showed that PdCr film TaN film has a very good protection effect, maked the measured temperature and the repeatability of the strain gauge a larger increase.Finally, on the basis of the study which are the best preparation technology about the TaN thin films strain gague were deposited on the surface of Al2O3 ceramic substrate. This paper further studied the film strain gauges which prepared on the surface of a Ni-base alloy substrate with multilayer structure, including NiCrAl Y attached layer, Al2O3 insulating layer, TaN sensitive layer and Al2O3 protection layer and achieved the miniaturization of the film strain gauges. The film strain gauges performances of the strain gauges prepared by optimized preparation technology are 7.87 of GF,-79.6 ppm/℃of TCR, the measurable temperature is 400 ℃.