Effective Thermal Conductivity of Metal Powders Using the Hot Disk Method

Thermal conductivity plays a crucial role in additive manufacturing (AM), aiding in simulations, optimizing processing parameters, assessing component quality, estimating porosity, etc. However, only a few techniques are available for measuring the thermal conductivity of initial powders, and even fewer instruments can assess thermal conductivity at each stage of the production process, from powders and green parts to sintered and fully dense parts.

In this work, the Hot Disk Transient Plane Source technique is proposed for thermal characterization due to its ability to simultaneously measure both thermal conductivity and thermal diffusivity in a single test, enabling the calculation of volumetric heat capacity. It allows the characterization of both solid samples and powders, accommodates a wide range of sample sizes (from a few millimeters and larger), and can differentiate between through-plane and in-plane thermal properties.

This presentation will demonstrate the Hot Disk method applied to copper, tungsten, 17-4PH steel, and 316L steel powders at room temperature and to 304 steel, Ti-6Al-4V, Inconel 718, Al-Mn-SC, Al-Si7-Mg6 powders up to 750 ºC. Thermal conductivity is evaluated, revealing correlations with material type, powder density, particle size distribution, and temperature. The talk will conclude with a discussion on how the measured thermal conductivity compares with the estimated values of a predictive model commonly used in numerical simulations for metal powders.