Influence of melt chemistry and gas atomization parameters in predicting d50 of austenitic stainless-steel powders

The Lubanska equation is one of the established models for predicting the median particle size d 50 of atomized powders. It accounts for the influence of thermophysical properties of the melt and atomizing gas parameters. Additionally, it includes a coefficient K, which is considered to reflect the characteristics of the atomizer. However, originally, it was suggested that K may depend on the liquid stream and particle shape. The aim of this study is to test this hypothesis using austenitic steel powders. Twelve atomizations of Cr16Mn7Ni4.5 steel were carried out, and additional literature data for powders produced using the same equipment were analysed. Initial an average K value for all powders was 39.99 ± 13.13 μm. After the data was grouped into three regions, corresponding to different nickel contents: 4.5, 6, and 9 wt%. Nickel, being a strong austenite stabilizer, affects phase transformation temperatures and lattice structure. As a result, it was established that K depends on the chemical composition. For austenitic stainless steels, the chromium equivalent Cr eq and nickel equivalent Ni eq are usually used to show the influence of alloying elements. Accordingly, the following correlations were identified for the studied steels: ∆Tsol = f(Ni eq /Cr eq ), d 50 = f(Ni eq /Cr eq ), and d50 = f(∆T sol ). Additionally, for steels with 9 wt% Ni, a a different behavior was observed depending on manganese content. Four distinct K values were determined: K Ni4.5 = 54.07 ± 2.71 μm, K Ni6 = 30.49 ± 4.14 μm, K Ni9Mn3 = 31.96 ± 4.44 μm, K Ni9Mn7 = 23.33 ± 6.12 μm, confirming that K is influenced by the chemical composition. • Constant K in Lubanska equation reflects both the features of atomizer design and influence of melt chemical composition. • Median particle size (d 50 ) varies with the chemical composition. • For austenitic stainless-steel influence of chemical composition is described with Cr eq and Ni eq. • MnS formation temperature significantly affects particle refinement. • Melt superheat influences d 50 only within a specific temperature range.