A novel in-situ gas-phase alloying approach in wire arc additive manufacturing for controlling solidification mode and designing hybrid stainless steels

Date

2025-11-01

Author

Chiniforoush, Elina Akbarzadeh
Jandaghi, Mohammad Reza
Moverare, Johan
Saeid, Tohid
Yurtışık, Koray

Metadata

Show full item record

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Item Usage Stats

2487
views

397
downloads

Cite This

This study presents a thermodynamically guided in-situ gas-phase alloying approach in wire arc additive manufacturing (WAAM) to enhance duplex stainless steels by shifting the primary solidification mode from δ-ferrite to γ-austenite, producing a nitrogen-enriched alloy with a continuous austenitic matrix that combines duplex-grade strength with superior ductility. Thermodynamic calculations guided nitrogen adjustment in the shielding gas to control solidification and develop high-performance microstructures. Thermodynamic–kinetic modeling predicted nitrogen uptake from the arc plasma, enabling gas composition selection to promote a shift from δ-ferrite to γ-austenite as the primary solidification phase. Nitrogen content analysis and Scheil simulations confirmed a transition to austenite-first solidification at approximately 0.7 wt% nitrogen. Electron Backscatter Diffraction and optical microscopy revealed that nitrogen-enriched (HN) samples exhibited a continuous γ-austenitic matrix with finely dispersed δ-ferrite, whereas nitrogen-lean (LN) samples had a δ-ferritic matrix with isolated γ-austenite islands. HN samples showed greater grain orientation spread, indicating increased internal misorientation. Despite pronounced crystallographic texture, the HN samples demonstrated nearly isotropic tensile behavior along with enhanced yield strength, tensile strength, ∼11 % higher hardness, and improved elongation. These findings demonstrate that melt chemistry control via gas-phase alloying enables phase-engineered microstructures with superior mechanical performance without modifying the filler wire.

Subject Keywords

Austenitic stainless steel, Duplex stainless steel, Gas phase alloying, Thermodynamic–kinetic, Wire arc additive manufacturing

URI

https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=105016095960&origin=inward
https://hdl.handle.net/11511/115819

Collections

Welding Technology and Nondestructive Testing Research and Application Center (KTTMM), Article