Neutron diffraction assessment at extreme temperatures to gain insights into the performance of thermocouple coatings

This project investigates the behaviour of Chromel-Alumel K-type thermocouples under extreme temperature conditions, focusing on coatings produced through thermal spray processes. These thermocouples, widely used in industrial and aerospace applications, experience phase changes that can compromise temperature accuracy, particularly in cryogenic environments. While bulk material behaviour is well-documented, the performance of thin films and coatings remains poorly understood, especially under high and low temperatures. The proposed study employs neutron diffraction to assess in-situ phase transformations and residual stress effects in Ni–20Cr coatings. Neutron diffraction's deep material penetration and high resolution make it ideal for probing changes across coating thicknesses. The project will investigate the influence of residual stress on phase transformations, contributing to improved thermocouple calibration and performance in cryogenic and high-temperature applications. By addressing these material challenges, the research aligns with ongoing UK government initiatives to digitalize manufacturing processes, building on previous EPSRC-funded projects and supporting the completion of a PhD thesis on thermal spray coatings with embedded sensing capabilities.