Metal Powders via Surface Grinding: Applicability and Performance Evaluation for Laser Sintering

Abstract

Commercial metal powders used as feedstock for additive manufacturing (AM) applications are primarily produced via gas or water atomization techniques. These are highly capital-intensive and inflexible, making the resulting powders as much as 3–10 times more expensive than corresponding cast ingots. Recently, we have demonstrated a potential alternative route for making metal powders — using surface grinding. The resulting powders have shown promise for use as stock in metal directed energy deposition (DED) processes. This work explores the applicability of these alternatively produced powders for laser sintering and related applications. Spherical metal powder particles (AISI 52100, SS 304) in the range of 5–100 microns were first produced using surface grinding. These powders were post-processed and segregated into monodisperse and polydisperse batches, representing high quality-low yield and low-quality-high yield stock, respectively. A high-power fiber laser source of 50 microns spot diameter was used to sinter these two stock powders, with nitrogen as a shielding gas, and their performance was evaluated using a range of ex situ analysis techniques. The latter included metallography, SEM/EDS and XRD analysis and was used to evaluate sintering quality in both cases, including melt pool and heat-affected zone characterization. Based on these results, we present recommendations for the use of mono- and polydisperse metallic powders and demonstrate the potential utility of using grinding as an alternative technique for the production of metal powders for laser sintering applications.