In-situ Inspection of Laser Powder Bed Fusion Ti-6AL-4V Additive Manufacturing using an Infrared Sensor

Additive manufacturing of metallic structures requires nondestructive evaluation (NDE) to ensure part quality. For large parts with complex geometries, post build NDE can be challenging using conventional techniques such as ultrasound or X-ray computed tomography. In-situ NDE offers some advantages during the build process such as layer by layer inspection, potential to correct for detected defects, and stoppage of the build if significant defects occur. In-situ NDE can provide input to validate defect prediction models that are necessary to predict the fatigue life performance of a built part thus allowing a computationally informed framework for part certification. In this work we utilize a high speed near infrared (NIR) camera within a configurable architecture additive testbed (CAAT) system for the in-situ inspection. The NIR camera is co-axially aligned with the laser within the CAAT system and records the melt pool and the transient cool down areas after solidification of Ti-6Al-4V laser powder bed fusion builds. Detection of defects, layer by layer, consists of processing the thermal data for differences in the transient cool down temperature responses after solidification. The thermal data is analyzed with a focus on the detection of lack of fusion porosity and near surface keyhole porosity. The results are compared to X-ray CT for validation.