Horizontal Oxidation Diffusion Behavior of MEMS-Based Tungsten-Rhenium Thin Film Thermocouples

Abstract

Tungsten-rhenium thin film thermocouples (TFTCs) are well suited for the surface temperature monitoring of hot components due to their small size, rapid response and low cost. In this study, a tungsten-rhenium TFTC with SiC protective film on all parts except the pads was fabricated by a microelectromechanical system (MEMS) process. During the low to medium temperature (−40 °C to 500 °C) repeatability test phase, the thermal voltage from the TFTC agreed well with that of the standard tungsten-rhenium thermocouple. However, during the high temperature test phase, the TFTC lost electronic response at around 620 °C. Failure analysis of the TFTC tested at 620 °C was performed by microscopy, scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), laser scanning confocal microscope (LSCM) and statistics. The results showed that the pads were oxidized without the protective layer, the number of oxidized protrusions distributed in this TFTC from the pad to the node decreases more and more slowly and the size of the oxidized protrusions also becomes smaller and smaller. This demonstrates the presence of horizontal oxidation diffusion in TFTCs, further illustrating the importance of pad protection and provides a direction for the subsequent structural optimization and the extension of the service life of TFTCs and other sensors.

High-Temperature Failure Evolution Analysis of K-Type Film Thermocouples

“…However, even though tungsten-rhenium alloys have high melting points and are coated with an SiC protective layer on TFTCs, they still experience failure when the environmental temperature reaches 620 • C, leading to a loss of thermoelectric output. This failure in TFTCs is attributed to horizontal oxidation diffusion, as observed in the failed TFTCs in [10]. In Zhao's study, the microstructural evolution of S-type TFTCs composed of Pt-10Rh and R-type TFTCs composed of Pt-13Rh was investigated at high temperatures.…”

“…Due to the high melting point and thermal stability of semiconductor materials, this kind of TFTC typically operates at higher working temperatures, and its output thermoelectric potential at the same temperature is higher than that of metallic material TFTCs. However, metallic material TFTCs offer higher temperature measurement accuracy and faster response times [5,10].…”

Optimization of Sustainable Production Processes in C45 Steel Machining Using a Confocal Chromatic Sensor

“…[7] employed a high-speed 3D camera system. The authors of [8] investigated the application of CCHS for assessing the surface properties of product layers in [9]. However, the machining process itself can be significantly influenced by factors such as surface topography and microhardness [10][11][12], surface roughness [10,11,13], residual stress [14][15][16], and microstructure [17].…”

Flexible thin film thermocouples: From structure, material, fabrication to application

“… 30 , 33 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 Due to these characteristics, they are used in several industrial, scientific, and consumer applications such as process control, ovens, furnaces, and automotive engines. 39 , 43 , 45 , 50 , 51 , 52 , 53 , 54 , 55 Based on the type of alloys used, several varieties of thermocouples are available for commercial use, such as Type K (nickel-chromium alloy and nickel-silicon alloy), Type J (iron and copper-nickel alloy), Type T (copper and constantan), Type B (platinum-rhodium alloy and platinum-rhodium alloy), Type S (platinum-rhodium alloy and platinum, Type R (platinum-rhodium alloy and platinum) and Type E (nickel-chromium alloy and constantan). Due to the distinct material characteristics of these thermocouple varieties, each of them has a different operation temperature range.…”