Research on Failure Mechanism and Thermal Stress of Thin-film Thermocouple at High Temperature

Aiming at the reliability of thin-film thermocouples applied to turbine blades at high temperatures, combined with high-temperature tests and finite element analysis, this paper studies its failure mechanism and thermal stress under thermal load. Multi-layer thin-film thermocouple samples were prepared on ceramic substrate, and high-temperature tests were carried out under different temperature loads, and the phenomenon of film shedding and cracking was observed using electron microscope. This paper analyzes the failure mechanism of the film sensor based on the function and structure, and uses ANSYS to analyze the thermal stress distribution of the film under high temperature load. Combining several existing theoretical models, this paper analyzes the factors affecting the thermal stress of the film and conducts simulation verification.

A Study on the Interface Diffusion of In2O3/ITO Multilayer Thin-Film Thermocouple

In2O3/ITO multilayer thin film thermocouple is a new type of semiconductor thin-film thermocouple, which has broad application prospects. The interface diffusion between the layers is the main cause of its thermal oxidation failure. In this paper, an interface diffusion model of multilayer films is established based on Fick's second law. A sample of In2O3/ITO thin-film thermocouple was prepared, then designed and conducted high temperature test. According to the test results, the diffusion of substances between the film layers was analyzed. Based on the established interface diffusion model, a simulation calculation is carried out. The influence of interface diffusion on the life of In2O3 and ITO sensitive layer was quantitatively analyzed.

Research on Interfacial Diffusion Reliability Model of Thin Film Thermocouple

Thin film thermocouple (TFTC) is widely used in high temperature measurement, which is of short response time, less heat residual and integrated structure. Due to the ultra-thin structure of TFTC, the interfacial diffusion has a great influence on its reliability when exposed to high temperature environment, which leads to its performance degradation. Taking thermocouple on the turbine blade as research object, the parallel diffusion model of multilayer thermocouple is proposed based on Fick’s law. The reliability model of the protective layer, the sensitive layer and the insulating layer are established in the basis of the parallel diffusion model. According to the logical correlation among the multilayer films of TFTC, the TTF model of TFTC is given. Finally, an example of reliability model based on multilayer diffusion is simulated by Monte Carlo method, which demonstrates the feasibility of the method and model.

Thermal and Vibration Mechanical Reliability of Multicoat Compound Thin-Film Thermocouple

For the thin-film thermocouple with ITO/In2O3 as the functional layer, the mechanical reliability of their composite multilayer membrane structures under high temperature and random vibration conditions are discussed. Using the elastic plasticity model based on the finite element simulation method, the stress and strain distribution patterns caused by the thermal mismatch and vibration of multilayer film materials are systematically analyzed, and the distribution of the stress concentration and strain accumulation regions that may lead to fatal reliability problems are characterized. When a thermal load of 1000 °C is applied, the protective layer of the structure is vulnerable to severe stress environment. In addition, plastic deformation occurs in the adjacent layers of the functional layer, making it a weak reliability area. The stress generated by the vibration load is much smaller than the thermal stress, which mainly occurs at the roots of the structure, where prolonged loading may lead to fatigue failure.