Influence of water atomization pressure on the preparation of 420 stainless steel powder by combined water–gas atomization

To prepare low-oxygen, fine-grained 420 stainless steel powder with uniform particle size distribution suitable for metal injection molding (MIM) of small-modulus gears, this study employed a combined water–gas atomization method. The systematic investigation examined the influence of water atomization pressure (90–120 MPa) on key powder properties, including particle size distribution, microstructure, oxygen content, flowability and tapped density. Additionally, the study explored the enhancement of powder storage stability through pre-oxidation treatment. Results indicate that increasing water atomization pressure reduced the median particle size (D₅₀) from 12.10 μm to 8.9 μm, narrowing the particle size distribution. The overall sphericity of the powder is good, remaining at a moderate level under different pressures, while oxygen content decreased from 0.35% to 0.17%. Powders prepared at 115 MPa exhibited optimal comprehensive properties: uniform particle size distribution, sphericity of 0.91, oxygen content of 0.17% and tapped density of 4.53 g/cm³. Following pre-oxidation treatment at 200 °C and 300 °C, the oxidation rate during storage was significantly reduced, with oxygen content ultimately stabilizing around 0.26%. This study provides theoretical foundations and process references for the preparation of high-performance stainless steel powders for MIM applications.