Finding the limits of single-track deposition experiments: An experimental study of melt pool characterization in laser powder bed fusion

Abstract

This work identifies sources of error in melt pool characterization tests that are frequently employed to study processing parameters in laser powder bed fusion (L-PBF) additive manufacturing (AM). At an early stage in process parameter development, researchers typically characterize the shape of single, non-overlapping melt tracks formed with varying processing conditions such as laser power and scanning velocity. However, as L-PBF enters mainstream manufacturing, researchers must test the limits of these commonly relied-upon characterization experiments to avoid errors that could impact process development. Hence, this study expands on conventional methods by depositing single-tracks and overlapping multitracks on a powder layer at multiple interpass temperatures, thereby mimicking heat buildup during the manufacturing of a multilayer part. While single-track melt pool depth and width do not increase as a function of interpass temperature as expected, multitrack experiments demonstrate a clear gradient in both melt pool depth, width and bead height between the first and final tracks. This work quantitatively demonstrates that the setup of single-track characterization experiments has a notable impact on the process parameter development. Alternatively, multitrack experiments closely capture the deposition conditions and melt pool variability observed during multilayer part fabrication.

Keywords

• Laser powder bed fusion
• Process window
• Melt pool geometry
• Interpass temperature
• Inconel 718