Work

Influence of gas type on microstructure and characteristics of super duplex stainless steel alloy powders prepared via gas atomization

Year: 2025

Type: article

Abstract: Conventional powder preparation methods, such as ball milling, often fail to produce fine, uniform, and spherical metal powders, limiting their suitability for advanced powder metallurgy (PM) and additive manufacturing (AM) applications. In this study, super duplex stainless steel (SDSS) powders with predominantly spherical morphologies were produced via gas atomization using nitrogen (N 2 ) and argon (Ar), and their microstructural, mechanical, and rheological characteristics were compared. N 2 -atomized powders, benefiting from its higher kinematic viscosity, exhibited finer particle size distributions. Surface analysis revealed Mn–Cr spinel, Fe and Si-based oxides, and NiO on both powders, with Cr 2 O 3 and Si 2 N 2 O unique to N 2 and MoO 2 /MoN to Ar. Cr-rich oxides were more pronounced in the N 2 condition, consistent with nitrogen-induced nitridation/oxynitridation during atomization. Microstructural investigation showed ferrite phases within grains and austenite phases along grain boundaries, resulting from the segregation of austenite-stabilizing elements (N, Ni, and Mn) during solidification. No significant difference in flowability was observed, as both powders exhibited excellent flow characteristics. Nanoindentation results indicated that austenite regions exhibited ∼18 % higher hardness and ∼11 % higher stiffness than ferrite regions. Overall, N 2 atomization refined grains, increased the austenite fraction, and enhanced hardness by ∼5.8 % in nanoindentation and ∼30 Hv in Vickers microhardness compared with powders prepared using Ar. These findings provide valuable insights for optimizing powder design and tailoring mechanical performance in PM and AM applications.

Source: Journal of Materials Research and Technology

DOI: 10.1016/j.jmrt.2025.09.003