Investigation of travel speed effects on microstructure and corrosion behavior of duplex stainless steel in wire-based DED additive manufacturing

In wire-based Direct Energy Deposition additive manufacturing, heat input is a key factor in adjusting wall thickness and can be controlled through travel speed. This study examines travel speed’s effect on the microstructure and corrosion behavior of duplex stainless steel (DSS). Two walls, DSS-7 and DSS-14, were deposited under identical parameters but with travel speeds of 7 mm/s and 14 mm/s, corresponding to heat inputs of 0.41 KJ/mm and 0.21 KJ/mm. Inverse pole figure maps showed weaker textural components along the build direction in DSS-14, with the maximum intensity values of both γ-austenite and δ-ferrite phases reduced by approximately 52%. The grain boundary map revealed a higher density of low-angle grain boundaries in DSS-14, indicating more residual strain, further supported by Kernel Average Misorientation analysis. LECO analysis revealed 47% higher oxygen content in DSS-14, supporting the increased formation of complex oxide inclusions observed in the microstructural results. A significant difference was observed in the size and distribution of acicular secondary austenite regions. In DSS-14, these regions exhibited a finer microstructure, which can be attributed to the higher cooling rate, and were associated with increased Grain Average Misorientation (GAM), greater residual strain, and more extensive plastic deformation. Corrosion tests showed higher corrosion resistance for DSS-7, with a higher corrosion potential (-23 mV vs. -69 mV) and 12.5 times lower corrosion current (3.9 μA/cm 2 vs. 49 μA/cm 2 ). The EIS measurements confirmed a 1.7× thicker, more stable quasi-passive layer in DSS-7.