Solidification behavior and texture of 316 L austenitic stainless steel by laser wire directed energy deposition

The solidification behavior and crystallographic texture of 316 L austenitic stainless steel builds fabricated via laser-wire directed energy deposition additive manufacturing (AM) were investigated. Shielding gas set-up and build type (single-track vs. multi-track) was varied, which led to changes in the solidification conditions and final build compositions. Primary δ-ferrite solidification is predicted based on equilibrium thermodynamic predictions of bulk feedstock composition. However, increasing solidification velocity of the AM process promotes solidification mode transition from primary δ-ferrite to primary austenite. Skeletal δ-ferrite and lathy δ-ferrite associated with primary δ-ferrite solidification and interdendritic δ-ferrite with primary austenite solidification were observed among the laser-wire directed energy deposition walls. Skeletal and interdendritic δ-ferrite exhibited a (001)δ // (001)γ parallel relationship with austenite and a {001} solidification texture aligned with the build for both austenite and δ-ferrite. Lathy δ-ferrite exhibited a Kurdjumov-Sachs orientation relationship, (101)δ//(11¯1)γ, with austenite due to austenite nucleation in the solid state. It is shown that the solidification behavior of AM 316 L is accurately represented by as-built composition data and a dendrite growth model, which combined, encompasses compositional and solidification condition impacts on the solidification pathway.