Numerical Prediction of Deformation‐Induced Martensitic Transformation in Cold‐Sprayed Austenitic Stainless Steel

The present work assesses the feasibility of depositing stainless steel powders using the cold spray (CS) deposition process. Specifically, the deposition of austenitic stainless steel powders, such as SS304 grade onto the same substrates, is evaluated for suitability in marine applications, particularly in hydraulic systems. X‐ray diffraction analysis confirmed martensitic transformation in CS SS304 coatings, with the transformed martensite volume fraction of 36.0%, depending on deposition processing parameters. Analytical 1D isentropic gas dynamic modeling, numerical simulations of particle impact, and experimental CS deposition are employed to explore martensitic transformation during deposition. The analytical work revealed that spraying 20 μm 304 stainless steel particles using helium at 473 K and 2.0 MPa with a commercially available nozzle can reduce particle temperature to 217 K, below the martensitic start ( M s ) temperature, facilitating martensitic transformation during deposition. Extending the nozzle's diverging section further enhanced the cooling effect, enabling nearly complete martensitic transformation in the deposited coating. Numerical simulations predicted a ≈40% localized martensite volume fraction at impact velocities of 1,000 m s −1 , with transformation favoring regions of low to moderate deformation (strain: 0.3–1.0). This study provides insights into tailoring microstructures of CS coatings for enhanced mechanical properties through controlled martensitic transformation.