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Simultaneous Measurements of Keyhole Depth and Absolute Absorptance During Stationary Laser Irradiance



Troy Allen, Wenkang Huange, Jack R. Tanner, Wenda Tan, James Fraser, Brian Simonds


Understanding the underlying physics of laser welding and metal additive manufacturing (AM) is crucial to the advancement of laser-based manufacturing. One aspect that especially requires careful attention and control is the formation and evolution of vapor depressions, or keyholes, within the melt pool. The dynamic geometric behavior of these depressions is intrinsically linked to the instantaneous energy coupled into the system, and therefore has a dramatic e ect on the nal properties of the material. In this work, we combine integrating sphere radiometry and inline coherent imaging to simultaneously measure time-resolved absorptance and vapor depression depth during stationary, high-irradiance laser illumination of a metal surface. This allows for the rst time, the exploration of the complex interdependence between energy coupling and geometry that underpins important industrial processes like laser welding and additive manufacturing. Time-resolved data reveals a general correlation between vapor depression depth and absorptance at high laser irradiance, showing that geometric e ects lead to an increase in absorptance from about 0:4 up to 0:9. There is also speci c correlation with temporal features such as vapor depression initiation and oscillation frequency during periods of instability. An understanding of traditional welding regimes, conduction and keyhole mode, is enhanced by revealing distinguishing time-resolved features, and a transition mode is shown that exhibits behavior of both regimes. Finally, the experimental results are compared with ray-tracing simulations, which provide validation and explanation of the results. The work presented here provides new insight into the underlying physics of laser-based manufacturing that can be used to advance progress towards deterministic control of the process.
Nature Communications


Laser welding, additive manufacturing


Allen, T. , Huange, W. , Tanner, J. , Tan, W. , Fraser, J. and Simonds, B. (2020), Simultaneous Measurements of Keyhole Depth and Absolute Absorptance During Stationary Laser Irradiance, Nature Communications, [online],, (Accessed July 14, 2024)


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Created June 28, 2020, Updated October 12, 2021