Session: 02-11-02: Session #2: Laser-Based Advanced Manufacturing and Materials Processing

Paper Number: 95817

95817 - Using High-Speed Thermal Imaging to Understand Melt Pool Defects in Laser Powder Bed Fusion 

Understanding of the temperature fields in metal-based AM systems is limited and represents a key challenge in process monitoring improvement. One of the major challenges associated with experimental temperature measurement methods in laser powder bed fusion (L-PBF) is the accelerated and localized heating and cooling of the process.  Temperature fields control the stability and dynamic behavior of the melt pool in L-PBF. Experimentally measuring the melt pool temperature using conventional infrared imaging techniques or pyrometry lack the speed and spatial resolution needed for extraction of melt pool temperature profiles. The goal of this project is to develop an experimental method to measure melt pool and surrounding temperatures using coaxial imaging with a color high-speed camera operating at 50,000 and 100,000 frames per second (fps). This method will create a real-time thermal imaging AM tool leveraging the principle of dual wavelength pyrometry. The use of a high-speed camera is necessary due to the high speed associated with the L-PBF laser operating speeds and other factors such as the change of phases and morphology during the process. Dual-wavelength pyrometry is advantageous because it is less sensitive to melt pool emissivity, plume transmissivity, and the camera’s view factor. Critical steps were taken to test the high-speed imaging system’s capabilities in measuring temperature. A NIST blackbody source thermal calibration of the high-speed imaging system was conducted to validate the setup’s experimental alignment with Planck’s blackbody theory. This calibration’s alignment with the system’s theoretical results serves as a foundation towards accurate temperature measurement. The results presented illustrate preliminary melt pool temperature fields for different commonly used L-PBF materials such as Ti-6Al-4V and 316L-SS. The temperature fields are captured at 50kHz and 100kHz with a resolution of 7.32µm during the processing of single bead scans at varying process parameter combinations. Using this technique, our team monitors the melt pool temperature on two laser powder bed fusion (LPBF) metal-based additive manufacturing systems: the EOS M290 and TruPrint 3000. Varying the filters in the high speed camera’s optical system and the camera’s parameters allows us to capture a wider temperature range. This high speed system has been developed with the objective of capturing the peak temperature and the solidification region of a melt pool. Imaging a variety of combinations of power and velocity from a given material’s process map, we associate the temperature fields to the corresponding defect regime with a favorable comparison with post-processing melt pool width measurements.

 

 

Presenting Author: Alexander Myers Carnegie Mellon University

Presenting Author Biography: A mechanical engineering graduate student at Carnegie Mellon University in Pittsburgh, Pennsylvania, Alexander Myers researches novel process monitoring techniques for metal additive manufacturing. He graduated summa cum laude with his Bachelor of Science in Mechanical Engineering from Pennsylvania State University in 2021, and he is currently a National Science Foundation Graduate Research Fellow.

Authors:

Guadalupe Quirarte Carnegie Mellon University
Alexander Myers Carnegie Mellon University
Syed Uddin Carnegie Mellon University
Jonathan Malen Carnegie Mellon University
Jack Beuth Carnegie Mellon University