Investigation of anisotropy in wire arc additively manufactured HSLA steel: Microstructural, mechanical, and corrosion analysis

This study investigates the process–structure–property relationships of a GMAW (gas metal arc welding)-based WAAM (wire arc additive manufacturing)-fabricated HSLA (high-strength low-alloy) steel wall using 3D Print AM 70 steel wire (8MnNiMoCrSi7–6–5). The aim is to evaluate the performance of the optimized ER100S-G solid wire in WAAM, focusing on potential anisotropy along the build direction and different loading orientations. Detailed microstructural and crystallographic characterization of the WAAM-fabricated AM70 steel wall is conducted to assess microstructural features, phase evolution, crystallite size, and internal strain. Mechanical performance is studied through hardness, tensile, and Charpy impact tests, while corrosion resistance is analyzed using potentiodynamic polarization and electrochemical impedance spectroscopy. The results show that bainitic ferrite, martensite, and retained austenite phases are consistently observed across all regions (top, middle, bottom) of the wall, with cooling rate variations in multilayer deposition influencing phase proportions without significant anisotropy. Crystallite size and microstrain vary slightly across regions, with the top region exhibiting finer grains and higher microstrain. Hardness, tensile properties, and impact toughness are generally uniform with limited anisotropy, although yield strength and impact toughness show some directional variation. Corrosion analysis indicates marginal anisotropy, with slight differences in charge transfer resistance and anodic and cathodic responses.