研究目的
To measure the spatial position of a laser beam relative to the radiance temperature distribution in the melt pool during laser powder bed fusion process thermography.
研究成果
This research demonstrates a method to measure laser spot position relative to the radiance temperature distribution of the melt pool during LPBF single-track scans. The displacement of the peak radiance temperature relative to the laser spot is statistically distinguishable. With increasing power to speed ratio, melt pool temperature isotherms increase in size and the peak radiance temperature moves forward relative to the scanning direction.
研究不足
The study is limited to the materials used (IN625 and Ti6Al4V) and the specific experimental setup. Future experiments will include a 850 nm reference laser spot and extend the temperature range to include the melt pool solidification boundary.
1：Experimental Design and Method Selection:
A high-speed, high magnification staring imaging system was constructed to observe the melt pool. A green laser was used to project a sharp spot on the working surface as a reference for the invisible hot laser.
2：Sample Selection and Data Sources:
Experiments were conducted on bare nickel alloy (IN625) and titanium alloy (Ti6Al4V) plates and repeated on single powder layers of the same respective alloy.
3：List of Experimental Equipment and Materials:
Custom LPBF system called the Additive Manufacturing Metrology Testbed (AMMT), high-speed camera, green laser (532 nm,
4：25 mW), hot laser (1070 nm, up to 500 W), transfer integrating sphere source (TISS), and thermally stabilized light-emitting diodes (LEDs). Experimental Procedures and Operational Workflow:
The staring imager was calibrated against a reference radiance source. The green laser and hot laser were statically positioned on a metal substrate, and their centroids were found. The hot laser was then scanned on the test substrate at specified power and speed, and high-speed images were acquired.
5：Data Analysis Methods:
The centroid position for the green laser spot and the melt pool peak were determined, and the difference in positions was found to determine the relative offset between the melt pool’s hottest spot and the center of the heating laser.
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