Unveiling Heat Treatment Effects on Hardness and Dimensional Properties of Power Bed Fusion‐LB/M/18Ni300 Turning Tool with Transpiration Cooling Channels

This study incorporates five different transpiration cooling channels, two circular, two hexagonal, and one novel bio‐inspired blood vessel that are designed in a monolithic turning tool and produced via metal additive manufacturing. They are heat treated under direct aging (DA1 and DA2) and solution heat‐treatment (SHT1 + DA1, SHT1 + DA2, and SHT2 + DA1) conditions to study the effects of heat treatment on the hardness and dimensions of complex internal geometries as they play a significant role in cooling effectiveness. Microstructural characterization for DA revealed the formation of lath‐type martensitic phases with uniform distribution, which improves the microhardness significantly, with SHT2 + DA1 achieving the highest hardness 641.2 HV and DA2 producing 611.7 HV. From the X‐ray microcomputed tomography, various heat treatments have very insignificant deviations in the dimensions of the transpiration channels (0.05% to 1%) from the as‐printed dimensions. Further, variations in design are not associated with the heat‐treatment process and the achieved hardness. This study helps create a standard operating procedure for heat treatment for complex internal channels with minimal dimensional deviations and highest hardness.