A Comparison of Solidification Structures and Submicroscale Cellular Segregation in Rapidly Solidified Stainless Steels Produced via Two-Piston Splat Quenching and Laser Powder Bed Fusion

Zachary Arthur Hasenbusch; Andrew Deal; Ben Brown; Davis Wilson; Laurentiu Nastac; Luke N Brewer

doi:10.1093/micmic/ozad065

A Comparison of Solidification Structures and Submicroscale Cellular Segregation in Rapidly Solidified Stainless Steels Produced via Two-Piston Splat Quenching and Laser Powder Bed Fusion

Microsc Microanal. 2023 Jul 25;29(4):1328-1349. doi: 10.1093/micmic/ozad065.

Authors

Zachary Arthur Hasenbusch¹, Andrew Deal², Ben Brown², Davis Wilson², Laurentiu Nastac¹, Luke N Brewer¹

Affiliations

¹ Metallurgical and Materials Engineering, The University of Alabama, 3043 H.M. Comer, 245 7th Avenue, Tuscaloosa, AL 35487, USA.
² Department of Energy's National Security Campus, Honeywell Federal Manufacturing & Technologies, Botts Road, Kansas City, MO 14520, USA.

PMID: 37488830
DOI: 10.1093/micmic/ozad065

Abstract

Fusion-based additive manufacturing techniques leverage rapid solidification (RS) conditions to create parts with complex geometries, unique microscale/nanoscale morphological features, and elemental segregation. Three custom composition stainless steel alloys with varying chromium equivalence to nickel equivalence ratio (Creq/Nieq) between 1.53 and 1.95 were processed using laser powder bed fusion (LPBF) and/or two-piston splat quenching (SQ) to produce solidification rates estimated between 0.4 and 0.8 m/s. Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were utilized to collect high-resolution images, electron backscatter diffraction (EBSD) phase identification, and measure cellular segregation. Similar features were observed in both LPBF and SQ samples including phase and microstructure, nanoscale oxide particles, cell size, and segregation behavior. However, dislocation pileup was observed along the cell boundaries only in the LPBF austenite solidified microstructure. Targeted adjustment of the SQ feedstock Cr and Ni concentrations, within the ASTM A240 specification for 316L resulted in no observable impact on the cell size, oxide particle size, or magnitude of segregation. Also, the amount of Ni segregation in the ferrite solidified microstructures did not significantly differ, regardless of Cr/Nieq or processing technique. SQ is demonstrated as capable of simulating RS rates and microstructures similar to LPBF for use as an alternative screening tool for new RS alloy compositions.

Keywords: STEM-EDX; cellular solidification; laser powder bed fusion (LPBF); rapid solidification; two-piston splat quench.