Temperature Measurement of Laser-Irradiated Metals Using Hyperspectral Imaging

Dong-Xia Qu, Joel Berry, Nicholas P. Calta, Michael F. Crumb, Gabe Guss, and Manyalibo J. Matthews
Phys. Rev. Applied 14, 014031 – Published 10 July 2020

Abstract

Accurate noncontact surface-temperature measurements during laser-based materials processing remain challenging due to the difficulty of establishing reliable emissivity values as a function of temperature and wavelength. Direct measurement of emissivity is difficult, as the emissivity may be changing constantly in the laser-material interaction region, where the temperature gradients are extreme and surface displacement can complicate the measurement. Here, we present a hyperspectral imaging method using a multiwavelength camera to capture the spectral radiance in eight different bands and fit the wavelength-dependent radiance to Planck’s law. Time-resolved temperature measurements during microsecond pulsed-laser irradiation of a metal plate made of the titanium alloy Ti-6Al-4V provide temperature information about the irradiated surface with an estimated accuracy of ±10%. The extracted wavelength-dependent emissivity slope compares well with reported results for macroscale titanium melts obtained using IR spectroscopy, which measure temperature without any built-in assumptions about the emissivity. The results are directly applicable to temperature monitoring during welding, additive manufacturing, and semiconductor growth.

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  • Received 15 March 2020
  • Revised 23 June 2020
  • Accepted 25 June 2020

DOI:https://doi.org/10.1103/PhysRevApplied.14.014031

Published by the American Physical Society

Physics Subject Headings (PhySH)

General PhysicsCondensed Matter, Materials & Applied Physics

Authors & Affiliations

Dong-Xia Qu, Joel Berry, Nicholas P. Calta, Michael F. Crumb, Gabe Guss, and Manyalibo J. Matthews*

  • Lawrence Livermore National Laboratory, Livermore, California 94550, USA

  • *matthews11@llnl.gov

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Vol. 14, Iss. 1 — July 2020

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