Performance Testing of L-PBF Produced Honeycombs Out of IN625

Abstract

Laser Powder Bed Fusion (L-PBF) enables the production of complex metallic parts. Processes using pulsed wave (PW) laser radiation have been proven to be well suited to build thin-walled honeycomb structures. However, the behavior of these structures under load conditions remains mostly unexplored. The objective of this paper is to characterize L-PBF produced honeycombs by investigating their rub and leakage performance. A pulse modulated process based on previous studies is optimized for productivity and used to build L-PBF test samples out of Inconel 625 (IN625). The honeycomb cell geometry is adjusted for improved printability of the overhanging walls. Repeatable L-PBF production of honeycombs with a wall thickness of about 100 μm is confirmed. Conventionally manufactured honeycomb samples out of sheet metal are tested as reference. The rub experiments cover radial incursion rates of up to 0.5 mm/s and relative velocities of up to 165 ms−1 at incursion depths (ID) between 0.5 and 2.0 mm. Lower incursion forces are observed for the L-PBF components, with a higher degree of abrasion. The leakage tests examine the mass flow rate for pressure ratios between 1.05 and 2.0 at constant gap size and constant back pressure. The L-PBF honeycomb seals show a higher mass flow rate, with the slightly larger cell size and higher surface roughness appearing to be the main influencing factors. Overall, improved rubbing behavior and 10 % higher leakage than the conventional probes demonstrate the applicability of L-PBF for honeycomb sealing systems. Future performance improvements through dedicated L-PBF designs can be expected.