Fabrication Of NiCrALY Thin Film Strain Gauges

The exact value of strain caused by vibration and temperature on hot components of engine should become an important part of the development of stable aviation engine. Thin film strain gauge is directly deposited onto the surface of aero engine’s hot components by using vacuum sputtering deposition method. It has advantages of high sensitivity and high accuracy, can be used in the harsh environment as like high temperature, high pressure and strong vibration. In this thesis, we made the multilayer structure for NiCrAlY thin film strain gauge on the surface of Ni based alloy substrate by using thin film technology.We study the parameters of sputtering NiCrAlY thin film and the effect of aluminum oxide and vacuum annealing. Finally, we test its electrical and strain properties from room temperature to 800℃. Main contents and conclusions are as follow:1. Study on the preparation of NiCrAlY thin films by RF magnetron sputtering. We study the influence of the substrate temperature and sputtering pressure on the properties of micro-structure, electrical properties and strain characteristics. The optimized process conditions are: sputtering power is 200 W, substrate temperature is 500 ℃, deposition time is 60 min, film thickness is about 1~2 μm, flow rate of Ar is 30 sccm, sputtering pressure is 0.3 Pa.Temperature coefficient of resistance(TCR) under this process conditions is 249 ppm / ℃, strain gage factor(GF) is 2.1.2. Study the self-passivating protection performance of NiCrAlY film and assess its stability and repeatability. We conduct experiments to prove that after oxidation treatment, the surface of the NiCrAlY generate a layer of Al2O3. It can improve oxidation resistance of the film. Then we conduct experiments to prove that the NiCrAlY thin film strain gauge is reliable and repeatable for use to 800 ℃.3. On the surface of the the nickel-based alloy substrate, we prepare a multilayer thin film strain gauge to meet the demand of strain measurement in the high temperature components of engine.Studies have shown that, the insulating properties of the YSZ/Al2O3 are still good enough up to a temperature of 800 ℃.It effectively realizes electrical isolation between the functional layers and the substrate. the relationship between strain and resistance change,the gage factor,itself varies with temperature,from room temperature to 800 ℃, the GF value changed from 1.67 to 1.99. 0~800 ℃,the thermal output of NiCrAlY thin film strain gauge prepared in nickel-base alloy substrate is around 100 με/℃, at the temperature of 600 ℃, there is a maximum value of 163 με/℃.