Prediction of the powder catchment efficiency and melt track height in laser directed energy deposition

Abstract

Powder catchment and melt track height are foundational for build planning in powder blown laser beam directed energy deposition. However, the interconnected relationships of the catchment efficiency with laser parameters, powder size distribution, and carrier gas flow rate make build planning across machines and feedstock challenging without trial-and-error verification. The primary geometry-based catchment model from laser cladding assumes that this relationship is captured through knowledge of the particle stream and laser spot diameter. First, this work evaluated the applicability of the geometry-based catchment model across a range of AISI 316L powder sizes, carrier gas flow rates, and laser spot diameters. By measuring particle stream diameters from high-speed imaging, the geometry-based catchment model predicted catchment with a root mean squared error of 11.5% for single melt tracks. Second, recognizing the burden of deploying high-speed imaging, this work utilized Stokes number for rapid catchment prediction in place of the particle stream diameter. This approach predicted the catchment with a root mean squared error of 11.8%. Finally, the predicted catchment and laser spot diameter was used to predict the average melt track height with a root mean squared error below 75 $\mu$m. Thus, end-users can apply this Stokes number-based approach to accelerate build planning when using AISI 316L feedstock.