Closed-loop control of meltpool temperature in directed energy deposition

Authors

Ziyad M. Smoqi, University of Nebraska-LincolnFollow
Ben Bevans, University of Nebraska - LincolnFollow
Aniruddha Gaikwad, University of Nebraska-Lincoln
James Craig, Stratonics, Inc.
Alan Abul-Haj, ARA Engineering
Brent Roeder, R3 Digital Sciences
Bill Macy, Macy Consulting
Jeffrey E. Shield, University of Nebraska-LincolnFollow
Prahalada K. Rao, University of Nebraska - LincolnFollow

Document Type

Article

Date of this Version

3-2-2022

Citation

Materials & Design 215 (2022) 110508. https://doi.org/10.1016/j.matdes.2022.110508

Comments

Open Access

Abstract

The objective of this work is to mitigate flaw formation in powder and laser-based directed energy deposition (DED) additive manufacturing process through close-loop control of the meltpool temperature. In this work, the meltpool temperature was controlled by modulating the laser power based on feedback signals from a coaxial two-wavelength imaging pyrometer. The utility of closed-loop control in DED is demonstrated in the context of practically inspired trapezoid-shaped stainlesssteel parts (SS 316L). We demonstrate that parts built under closed-loop control have reduced variation in porosity and uniform microstructure compared to parts built under open-loop conditions. For example, post-process characterization showed that closed-loop processed parts had a volume percent porosity ranging from 0.036% to 0.043%. In comparison, open-loop processed parts had a larger variation in volume percent porosity ranging from 0.032% to 0.068%. Further, parts built with closed-loop processing depicted consistent dendritic microstructure. By contrast, parts built with open-loop processing showed microstructure heterogeneity with the presence of both dendritic and planar grains, which in turn translated to large variation in microhardness.