Impact of Surface Post-Treatments on the Properties of Additively Manufactured Ti-6242 Alloy

Metal additive manufacturing, particularly Laser Powder Bed Fusion (L-PBF), enables the fabrication of geometrically complex components such as those made from Ti-6Al-2Sn-4Zr-2Mo (Ti-6242). However, the as-built surface condition often exhibits high roughness and partially fused particles, which can negatively impact part life and wear resistance. This study focused on optimizing L-PBF process parameters to maximize relative density and minimize defects, followed by a comprehensive evaluation of mechanical, thermal, and chemical base surface post-treatment techniques: grinding, tumble finishing, laser polishing, and chemical polishing. Process optimization identified a parameter set—200 W laser power, 1000 mm/s laser scan speed— that achieved the highest density (~99%) and relatively low surface roughness, selected as the baseline for surface treatment trials. All post-processing methods significantly reduced surface roughness, with grinding achieving the greatest reduction, followed by tumble finishing, laser polishing, and chemical polishing. SEM analysis and roughness profiling revealed distinct mechanisms of surface modification, including plastic deformation, abrasive smoothing, and localized melting. Nanoindentation tests indicated that laser polishing slightly reduced near-surface hardness due to thermal relaxation, while tumble finishing caused localized strain hardening. These results highlight the importance of combining optimized build parameters with tailored surface finishing strategies to enhance the performance of Ti-6242 AM components, particularly for applications demanding high surface integrity and mechanical reliability.