Polycrystalline FeCrAl thin films used as high-pressure hydrogen environment strain gauges: Low zero-drift, creep, high sensitivity

High-pressure hydrogen systems' internal load sensors face challenges such as zero drift, creep, and response hysteresis, primarily due to hydrogen infiltration into traditional resistive strain gauges. To address this, we developed a novel polycrystalline FeCrAl film and fabricated an in-situ Cr/AlN/FeCrAl sandwich-structure thin-film strain gauge (TFSG) on a 316 L stainless steel substrate using magnetron sputtering and a template technique. Results indicate that substrate temperature significantly affects the microstructure and resistance of FeCrAl. At 400 °C, the uniform, fine body-centered cubic (bcc) polycrystalline film exhibits higher resistivity and resistance stability, while higher temperatures lead to grain coarsening and defect proliferation. Testing in a 12 MPa hydrogen environment shows that the Cr/AlN/FeCrAl TFSG outperforms traditional Cu–Ni strain gauges in hydrogen resistance, with zero drift and creep below 30με and a strain sensitivity coefficient of approximately 1.62, demonstrating high hydrogen resistance and practicality in high-pressure environments.