Closed-loop control of meltpool temperature in directed energy deposition. (March 2022)

• Record Type: Journal Article
• Authors: Smoqi, Ziyad; Bevans, Benjamin D.; Gaikwad, Aniruddha; Craig, James; Abul-Haj, Alan; Roeder, Brent; Macy, Bill; Shield, Jeffrey E.; Rao, Prahalada
• Is Part Of: Materials & design. Volume 215(2022)
• Publication Date: 2022-03
• Subjects: Directed energy deposition -- Closed-loop control -- Meltpool temperature -- Dual-wavelength pyrometer -- Microstructure -- Porosity; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2022.110508
• Languages: English
• ISSNs: 0264-1275

Abstract

Graphical abstract: 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.