Atomization pressure and delivery tube position coupling in 316L stainless steel gas atomization

To meet the growing demand for fine-particle-size, high-performance 316L stainless steel powder in additive manufacturing, the coupled effects of atomization pressure (3–8 MPa) and delivery tube extension length (−2 to +2 mm) on the gas atomization dynamics are investigated. Using computational fluid dynamics (CFD) coupled with experimental validation, the flow-field characteristics and particle size distribution in a close-coupled atomization configuration are analyzed. The results reveal that the aspiration pressure (ΔP) exhibits a non-monotonic trend with increasing pressure, reaching a minimum (−28 641.8 Pa) at 4 MPa and becoming positive beyond 6 MPa, which suppresses melt outflow and poses a risk of nozzle clogging. Tube extension elevates the flow velocity but markedly increases ΔP; for example, at 4 MPa, lengths exceeding +1 mm lead to a positive ΔP. Using ΔP < 0 as a stability criterion, a quantitative stable processing window is defined. Within this window, simultaneously increasing the pressure and employing moderate tube extension synergistically refines the powder and narrows the particle size distribution. The simulation predictions show good agreement with experimental data (an average error of 4.7% for D 50 at 4.5 MPa). This work provides a theoretical foundation and a practical processing window for producing high-quality 316L stainless steel powder.