Influence of Local Laser Power Distribution and Build-Plate Temperature on Porosity and Microstructure in Laser Powder Bed Fusion (LPBF)

Abstract:

Laser powder bed fusion (LPBF) parts are commonly fabricated using nominally uniform process parameters; however, local variations in thermal boundary conditions can significantly influence part quality. In this study, the spatial distribution of build-plate temperature during LPBF of Inconel 718 was experimentally characterized using a thermocouple grid, and its influence on porosity, microstructure and hardness was investigated. Despite a nominal build-plate set temperature of 180 °C, measured temperatures ranged from approximately 101 °C to 120 °C and exhibited a pronounced radial gradient from the center toward the edges of the build-plate. Cubic samples fabricated at locations corresponding to the highest and lowest local temperatures showed distinct microstructural differences, with higher temperatures promoting slightly coarser cellular–dendritic morphologies and lower hardness values. Although bulk volumetric porosity showed identical values for both locations (≈0.01 vol.%), the pore populations differed: the hotter location contained fewer but locally larger voids while the cooler location exhibited a higher number density of smaller pores, as shown by equivalent-diameter histograms and cumulative distributions. Samples produced at cooler locations exhibited finer microstructures and higher hardness. These results demonstrate that spatial non-uniformity in build-plate temperature can lead to local variations in microstructure and mechanical properties within a single LPBF build, highlighting the importance of characterizing local thermal conditions when establishing reliable process-structure property relationships.

• Periodical: Key Engineering Materials (Volume 1047)
• Pages: 259-265
• Online since: April 2026
• Authors: Chukwuemeka Okolo*, Sebastian Härtel
• Keywords: Build-Plate Temperature, Laser Powder Bed Fusion, Porosity

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