Multiscale Surface Characterization of LPBF-Fabricated 17-4 PH Stainless Steel TPMS and Flat Plates After Aging, Shot Blasting, and Hydrophobic Coating

Multiscale surface characterization is essential for understanding the surface condition of laser powder bed fusion (LPBF)-fabricated metallic structures and regions subjected to different post-processing conditions. This study examines LPBF-fabricated 17-4 PH stainless steel (SS) triply periodic minimal surface (TPMS) prototypes to characterize geometry-dependent manufacturing features and representative flat plate regions associated with aging, shot blasting, hydrophobic coating, and combined blasting-coating conditions. Hirox digital microscopy was used to examine macro- to microscale surface features on the TPMS prototypes and flat plates, while Hirox 3D profiling was used to evaluate the roughness response of the flat plate treatment regions. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) provided higher-resolution surface morphology and elemental composition from selected flat plate regions. Hirox imaging revealed anisotropic surface textures aligned with LPBF scan paths, pore presence, and staircase-like features on curved TPMS surfaces. Three-dimensional profiling identified different geometric mean Rz values among the examined flat plate regions; the blasted-plus-coated regions on the untreated baseline plate, U-BC, and the aged plate, A-BC, had the smallest reported values within their respective plate sets. SEM observations identified LPBF-related features, including balling, pores, particle adhesion, localized surface irregularities, and coating cracks. Localized EDS analysis showed Fe-, Cr-, Ni-, Cu-, and Si-containing elemental profiles in the examined U-0 and A-0 regions, whereas the analyzed U-C region exhibited strong Si and O signals, coating-associated elemental features, and reduced substrate contribution. These results demonstrate the importance of combining surface morphology, profile roughness, coating condition, and localized elemental composition to document geometry-dependent TPMS features and regional surface condition differences across the examined flat plates.