Layer-Wise Melt Pool Temperature Evolution in Laser Powder Bed Fusion: An Experimental Study Using a Single Camera Based Two-Wavelength Imaging Pyrometry

Abstract

In metal additive manufacturing (AM) the layer-wise thermal history is crucial for its effect on the print part properties, such as, microstructure, porosity, and mechanical strength. Literature studies for evaluating the part thermal history are typically based on in-situ infrared thermography and thermal modeling. However, the effect of melt pool temperature on the part thermal history has not been widely studied. In this preliminary work, for the first time we present a large and comprehensive in-situ monitored, layer-wise melt pool temperature evolution data for laser powder bed fusion (LPBF) AM. The melt pool temperature is evaluated using an in-house Single Camera Two-Wavelength Imaging Pyrometry (STWIP) system. The melt pool temperature evolution was evaluated for three different prints with different inter-layer-times and print heights. The melt pool temperature history trends presented in this work are in agreement with literature studies on part-thermal histories. The LPBF process signatures from our STWIP system can help develop more accurate thermal models with the melt pool temperature as the input and the unique capability of the STWIP system to acquire and analyze large amounts data facilitates the development of machine learning models for estimating part properties based on the process signatures.

Melt pool width measurement in a multi-track, multi-layer laser powder bed fusion print using single-camera two-wavelength imaging pyrometry

“…To meet the need, we have developed a unique in-situ LPBF process monitoring system, a single-camera two-wavelength imaging pyrometry (STWIP) system, along with an off-axis high-speed camera system [16]. Our STWIP system has excellent high-speed MP monitoring capabilities and demonstrated its merit in monitoring real-world print samples for 100's of layers and estimating their MP widths, MP temperature and MP temperature evolution [16,17]. Further, we have demonstrated [15,16,18] our system's capability in successfully estimating the MP width for single track prints, and MP temperature for MTML prints.…”