In situ monitoring is required to improve the understanding and increase the reliability of additive manufacturing methods such as laser powder bed fusion (LPBF). Current diagnostic methods for LPBF capture optical images, X-ray radiographs, or measure the emission of thermal or acoustic signals from the component. Herein, a methodology based on the thermal emission of electrons - thermionic emission - from the metal surface during LPBF is proposed which can resolve laser-material interaction dynamics. The high sensitivity of thermionic emission to surface temperature and surface morphology is revealed to enable precise determination of the transition between conduction and keyhole mode melting regimes. Increases in thermionic emission are correlated to laser scanning conditions that give rise to pore formation and regions where surface defects are pronounced. The information presented here is a critical step in furthering our understanding and validation of laser-based metal additive manufacturing.

需要现场监控以提高对增材制造方法（例如激光粉末床熔合（LPBF））的了解并提高其可靠性。LPBF的当前诊断方法可捕获光学图像，X射线射线照相或测量组件发出的热或声信号。在本文中，提出了一种基于电子热发射-热电子发射-在LPBF期间从金属表面发射的方法，该方法可以解决激光与材料相互作用的动力学问题。揭示了热电子发射对表面温度和表面形态的高度敏感性，从而能够精确确定传导和锁孔模式熔化机制之间的过渡。热电子发射的增加与激光扫描条件有关，激光扫描条件导致孔形成和表面缺陷明显的区域。此处提供的信息是进一步了解和验证基于激光的金属增材制造的关键步骤。