Effects of Sandblasting at Different Angles Combined with Subsequent Acid Pickling on the Microstructure and Surface...

Ti-6Al-4V alloy possesses excellent specific strength, corrosion resistance, and biocompatibility, rendering it widely applicable in aerospace, marine engineering and biomedical fields. Selective laser melting (SLM) serves as an effective technique for manufacturing complex Ti-6Al-4V components. However, SLM-formed specimens generally suffer from surface defects such as high surface roughness, adhered powders, spheroidized particles, and localized spatter, which degrade their service performance and limit further practical applications. Therefore, effective surface modification is urgently required. This work systematically explores the synergistic effects of sandblasting at various angles followed by acid pickling on the surface characteristics of SLM-formed Ti-6Al-4V alloy. The SLM Ti-6Al-4V samples were first treated by sandblasting at different impact angles and then subjected to acid pickling. Material mass loss, micro-morphology, surface roughness, contact angle, surface microhardness, abrasive-particle embedment and surface residual stress were measured and analyzed. The results show that sandblasting angle exerts a remarkable influence on material removal behavior, abrasive-particle embedment and near-surface mechanical response. Scanning electron microscopy (SEM) observations indicate that sandblasting at different angles can not only effectively eliminate surface-adhered powders, but also generate impact pits, cutting grooves, and ploughing marks whose morphologies vary with sandblasting angles. The subsequent acid pickling process further removes loose particles and sharp protrusions, and promotes the formation of microscale surface structures. Benefiting from the combined effects of mechanical sandblasting and chemical acid pickling, the alloy samples exhibit substantially reduced surface roughness and enhanced surface wettability. Meanwhile, sandblasting induces work hardening and thus increases surface microhardness and surface residual stress, while acid pickling regulates surface morphology and the state of the work-hardened layer to a certain degree. Overall, this study provides an economical, efficient, and industrially feasible composite surface modification approach to reduce surface roughness, enhance hydrophilicity, and tailor surface hardness of SLM Ti-6Al-4V alloy.