High Temperature Thermal Conductivity Measurement Using Two-Color Thermal Imaging

This research explores measuring the thermal conductivity of various materials at high temperatures (up to 4000 K). We use the two-color thermal imaging technique with a commercial color camera to measure the temperature distribution on a sample heated by the high-power laser heat source of a Directed Energy Deposition (DED) additive manufacturing machine. The technological requirement to evaluate materials for use in high temperature environments, particularly in the world of additive manufacturing and aerospace, has dramatically increased in recent years. Developing a technique capable of measuring the thermal conductivity of materials up to 4000 K will provide tremendous insights to improve the manufacturing process of different materials. Conventional methods such as the “flash” method have been improved to measure the thermal conductivity of materials up to 3000 K but this approach has challenges including the ability to reach higher temperatures. Electric pulse methods can also reach high temperatures but are applicable only to electrically conductive samples. Using the newly developed two-color thermal imaging method, we are capable of capturing the thermal conductivity of materials with high positional and temporal resolution. This study focuses on developing an apparatus to measure the temperature distribution of a material under a given heat source using the two-color imaging method, then deriving the temperature dependent thermal conductivity using least squares fitting with FEA models. We evaluate the robustness of our proposed method using materials with well-known high temperature thermal conductivity, such as Tungsten, Tungsten Carbide, and Tantalum.