High-temperature Stability Study And Performance Testing Of ITO Thin-Film Strain Gauges

The rapid rise of China’s aerospace,marine and engineering vehicle manufacturing industries has contributed to the development of the fields of mechanics of materials,electrical engineering and mechanical engineering,and requires that the components used in these fields can work stably under harsh conditions.As a highly complex thermal machine,the key component of a gas turbine engine,the turbine blade,is subjected to high temperatures,pressures and vibrations,making strain monitoring of hot end components such as turbine blades extremely important.Thin-film strain gauges have the advantages of small size,high accuracy and fast response,making them ideal for monitoring the strain on components,and ITO films are attractive for high-temperature strain gauges because of their high melting point,high electrical conductivity and good reliability.In this study,a series of performance tests at high temperatures were carried out using ITO films as strain gage materials.The main studies are as follows.1.ITO sensitive films were prepared on the ceramic surface by pulsed laser deposition technique and covered with Al N/Al₂O₃composite films and monolayer Al₂O₃film protection layers.The microstructures of ITO+Al N/Al₂O₃and ITO+Al₂O₃were characterised using SEM and XRD.The temperature coefficient of resistance（TCR）and resistance drift rate（Dr）of ITO thin film strain gages with and without protective films were tested from room temperature to 1100°C.The ITO strain gages prepared with an Al N/Al₂O₃protective layer showed the smallest TCR of-521ppm/°C and the smallest resistance drift rate of 0.0117/h.The strain gages prepared with an Al N/Al₂O₃protective layer showed the smallest TCR of-521ppm/℃and the smallest resistance drift rate of 0.0117/h.The strain gage prepared with the Al N/Al₂O₃protective layer was also maintained at 1100°C for 8 h with a Dr of 0.0155/h.It was also tested for cycling repeatability from room temperature to 1100℃and also showed excellent high temperature stability.Piezoresistive tests were carried out on three samples at800℃,where the ITO thin film strain gauge prepared with an Al₂O₃/Al N film protective layer had a better piezoresistive response,with an average gauge factor of-8.12 for three repeatability tests.2.ITO thin film strain gauges were prepared on the surface of nickel-based alloys.The Ni Co Cr Al Y transition layer and the high-purity Al₂O₃insulating layer were prepared by atmospheric plasma spraying,the ITO sensitive layer and the Al₂O₃protective layer were prepared by pulsed laser deposition,and finally the Pt leads were completed with conductive platinum paste.3.A high temperature strain gauge platform was built to test the thin film strain gauge.Firstly,the insulation performance was tested on high purity alumina,which showed excellent insulation performance at high temperatures with a resistance of 1 MΩat 1000°C and 325 KΩat 1100℃.Tensile tests were carried out on ITO thin-film strain gauges on nickel-based alloys,which showed a gauge factor of 5.63 at room temperature and 17.05 at 800℃.The GF of the ITO thin-film strain gauges increased with increasing temperature.