Characterization of Microstructure and Localized Corrosion Resistance of Heat-Treated 17-4 PH Stainless Steel Fabricated by Material Extrusion

The quality, reproducibility, and reliability of additive-manufactured parts strongly depend on optimizing printing parameters and post-processing treatments. This study evaluates the effects on the microstructure and corrosion resistance properties of solution annealing and aging heat treatments performed on 17-4 PH stainless steel samples fabricated with different build-up orientations using a material extrusion technology: the Bound Metal DepositionTM. The chemical composition and microstructures were determined using X-ray diffraction, chemical etching, optical microscopy, and scanning electron microscopy. The corrosion resistance properties in neutral sodium chloride electrolytes were investigated through cyclic potentiodynamic polarization and open circuit potential monitoring and analysis. The findings demonstrated that the solution annealing heat treatment remarkably enhanced the overall corrosion resistance properties of the samples. The improvement was attributed to the growth of the ferritic phase along the grain boundaries of the martensitic matrix and a finer dispersion of copper precipitates. The aging heat treatment performed after solution annealing enhanced the ferritic phase development, resulting in a further improvement of the localized corrosion resistance properties.