# title
A comprehensive in-situ monitoring framework for pore and uneven surface detection in electron beam powder bed fusion via electron-optical imaging

# abstract
Despite the advantages of electron-beam powder bed fusion (E-PBF), its broader adoption remains limited by rigorous qualification requirements and variability in part quality. In particular, recurring defects such as pores and uneven surface morphologies impede consistent part quality and complicate qualification efforts. This paper presents a comprehensive in-situ defect detection framework that targets these two primary defect modes. Although Grade 23 Ti-6Al-4V powders were used in this study, the framework itself is material-agnostic and can be applied to other powder systems. By leveraging electron-optical (ELO) imaging with four-quadrant backscattered electron detectors, hardware that is highly resistant to the harsh E-PBF environment, we detect anomalies on a layer-by-layer basis and correlate them with X-ray computed tomography (XCT) data across multiple layers. Additionally, we demonstrate that ELO-based surface reconstruction, combined with quantitative analyses, can identify and characterize uneven surfaces. This approach reveals how process instabilities drive uneven surface morphologies. Furthermore, we establish a statistically significant, causal relationship between powder recoat irregularities and evolving surface unevenness. While this study demonstrates that ELO can detect volumetric and topographic defects, it also identifies two main limitations: a spatial resolution of approximately 106m, and process instability that emerges in the later stages of a build due to metal-vapor deposition on the detector assembly. At the end of the results and discussion section, the paper discusses several potential solutions to these challenges to further improve the performance of ELO monitoring.

# authors[].organizations[].label
Texas A&M Engineering Experiment Station (TEES)

# authorList[]
Lee, K., Truong, D. T., You, H., Roy, P., Ghaffari, N., Karaman, I., & Andani, M. T.