Abstract
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.
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