Measurement of the thermal conductivity of cold gas dynamically sprayed alumina-reinforced aluminum coatings between − 150 °C and + 200 °C. New test method and experimental results

• Novel method to determine the thermal conductivity of thin coatings
• Alumina-reinforced aluminum coatings deposited by CGDS
• Very low thermal conductivities were measured and explained by microstructural coating features.
• Results of novel method were verified by a standard steady-state method.

A novel method has been developed to measure the apparent thermal conductivity of thin coatings based on measuring the heat flux through the coatings as well as the external heat transfer coefficient of an uncoated sample using a modified slug calorimeter configuration. The method was tested on cold gas dynamically sprayed alumina-reinforced aluminum coatings deposited on Al 7075 alloy substrates, and verified by a standard steady-state method. The very low apparent thermal conductivities measured between − 150 °C and + 200 °C have been attributed to the presence of numerous splat boundaries, pores and microcracks the width of which changes in response to temperature gradients and hence differential thermal expansion coefficients.