Synergistic influence of laser scanning strategies and heat treatments on the microstructure-mechanical property relationship of laser directed energy deposited austenitic stainless steel 304

This study systematically investigates the synergetic influence of laser scan strategy and post-processing heat treatment on the microstructure and mechanical properties of austenitic stainless steel 304 (SS304) fabricated using the Laser-Directed Energy Deposition (L-DED) process. Bulk SS304 samples were fabricated using four distinct infill scan rotation angles (45°, 67°, 83°, and 90°), followed by solutionizing heat treatment involving two quenching methods to evaluate microstructural evolution and mechanical properties. To identify an optimal process window, a full-factorial design of experiments (DoE) was initially employed using single-track deposits with varying L-DED parameters. The as-deposited (AD) and heat-treated samples with infill angles of 45° and 67° demonstrated a synergistic combination of high ultimate tensile strength and ductility. Electron Backscatter Diffraction (EBSD) analysis revealed weak crystallographic texture in both AD and heat-treated samples. The rotation during scanning across layers disrupted preferential grain growth and caused grain fragmentation in the AD samples. The solutionizing heat treatment further homogenized the microstructure, enhancing mechanical performance. This comprehensive study shows how the synergetic interplay between laser scan strategy and heat treatment can be deployed to tailor the microstructural integrity and mechanical properties of L-DED fabricated SS304, offering valuable insights for optimizing additive manufacturing processes.