Melt pool signatures of TiN nanoparticle dry-coated Co25Cr25Fe25Ni25 metal powder in laser-powder-bed-fusion. (February 2023)

• Record Type: Journal Article
• Authors: Gärtner, Eric; Witte, Arne; Peter, Nicolas J.; Devulapalli, Vivek; Ellendt, Nils; Dehm, Gerhard; Jägle, Eric A.; Uhlenwinkel, Volker; Mädler, Lutz
• Is Part Of: Materials & design. Volume 226(2023)
• Publication Date: 2023-02
• Subjects: Powder flowability -- Dry-coating -- Laser-powder-bed-fusion -- Pyrometry -- Melt pool signature; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2023.111626
• Languages: English
• ISSNs: 0264-1275

Abstract

Graphical abstract: Highlights: TiN nanoparticle dry-coating reduced power cohesion of a Co25 Cr25 Fe25 Ni25 metal powder (20–90 µm) and enhanced flowability and packing density. Dry-coating showed marginal variations of the powder reflection via UV–Vis spectroscopy. Thermal emissions from in situ confocal single-color pyrometry and ex situ solidified melt pool dimensions were predictive of conduction and keyhole fusion mode. Enhancing powder processability directly decreased melt pool signatures and significantly shifted keyhole and lack-of-fusion porosities in the P - v -space. Abstract: Metal powders in laser-powder-bed-fusion (L-PBF) often exhibit cohesive flow resulting from interparticle adhesion. Nanoparticle dry-coating can improve powder flowability and promote powder layer densification. A Co25 Cr25 Fe25 Ni25 metal powder (20–90 µm) is dry-coated with TiN particles with a diameter of 16 nm at low concentrations of up to 69 ppm. The dynamic angle of repose decreased and bulk powder density increased compared to the uncoated state from 49 ° and 4.67 g/cm 3 to 29 ° and 4.81 g/cm 3 with dry-coating of TiN, respectively. UV/Vis spectroscopy showed negligible alterations by TiN additions on the powder light absorption. The powder modifications strongly affected their corresponding processability in L-PBF and reduced the melt pool signatures of the in situ detected confocal single-color pyrometer signal as well as ex situ measured melt pool depth and width. With increasing flowability, a significant decrease in thermal emission and melt pool size was observed. The results demonstrate the impact of powder flowability and bulk powder density on the quality of L-PBF parts when particle interactions are actively modified.