Powder Thermal Conductivity Measurements in L-PBF Using Powder-Included Build Specimens: Internal Geometry Effect

Abstract

Abstract This study investigates the thermal conductivity of 17-4PH stainless steel powder that was encapsulated within specimens with different internal geometries in laser powder bed fusion (L-PBF) additive manufacturing (AM). The objective is to evaluate the effect of the internal geometry of the specimens on the measurement of the powder thermal conductivity and to compare the thermal properties amongst the 17-4PH and two additional powder materials used in L-PBF. Continued from the previous work [1], three new cone configurations in the hollow specimens were designed and fabricated in an L-PBF system. The thermal conductivity of the internal powder was indirectly measured using an experimental-numerical approach, combined with laser-flash testing, finite element (FE) heat transfer modeling and multivariate inverse method. The results reveal that the thermal conductivity of 17-4PH powder ranges from 0.67 W/(m·K) to 1.34 W/(m·K) at 100 °C to 500 °C, and varies with the internal geometry of the specimens. In addition, the measurement of the hollow specimen with a convex cone seems to be a more reliable evaluation. Further, the thermal conductivity ratio of the powder to the solid counterpart of 17-4PH approximately ranges from 3.9 % to 5.5 % at tested temperatures, which is similar to the results obtained from the nickel-based super alloy 625 (IN625) and Ti-6Al-4V (Ti64) powders measured in a previous study.