Ultrasensitive and Superfast Response Time NiCr Thin-Film Strain Rosettes Fabricated on Inconel 718 Substrates

The turbine blades in aeroengines are subjected to high-temperature stress fields, making them vulnerable to fatigue cracks, which can undermine engine performance. Rapid and precise strain monitoring is crucial for evaluating material properties’ deterioration and determining the lifespan of components. Existing strain measurement methods, predominantly noncontact-based, face certain limitations in practical applications. This article proposes a dynamic strain measurement system designed for NiCr thin-film strain rosettes utilizing a two-axis overlapping (0°/90°) technique. The strain sensor employs 0°/90° NiCr thin film fabricated using direct current (dc) pulsed magnetron sputtering and a thermal annealing strategy. Inconel 718 equal-strength beams were utilized as test specimens and finite element analysis optimized the sensitive grid design. A comparative investigation was conducted into the high-temperature insulating properties of single-layer Al₂O₃, single-layer SiO₂, bilayer SiO₂/Al₂O₃, and four-layer SiO₂/Al₂O₃/SiO₂/Al₂O₃ composite films. The four-layer composite insulating films, patterned 0°/90° NiCr thin-film sensitive grids, and Al₂O₃ protective films were sequentially deposited on Inconel 718 equal-strength beams. Post-annealing, the temperature coefficient of resistance (TCR) decreased by 21.28% from 353.038 to 277.906 ppm/°C, the gauge factor (GF) improved by 1.29% from 1.945 to 1.97, and the hysteresis error was reduced to 0.817%FS. The strain peak accurately tracked load variations with millisecond-level response and recovery times, demonstrating excellent dynamic response. The proposed thin-film strain sensors provide an effective solution for high-precision and rapid strain measurements for critical components such as aeroengine turbine blades.