Assessing sustainability of titanium powder recycling in additive manufacturing via powder surface and microstructural analysis for porous implant coatings

Titanium-based porous structures are critical for promoting osseointegration and enhancing biocompatibility in biomedical implants. However, significant powder wastage during the implant fabrication using additive manufacturing (direct energy deposition-DED) has major cost challenges, necessitating effective powder reuse strategies. Therefore, this study investigates the reusability of Ti powder generated as spatter during DED by systematically characterizing its powder surfaces and microstructure and assessing its reusage limitations for bio-implant applications. Surface analysis confirmed the presence of TiO 2 on all powders, with thickness increasing after recycling during DED; this enrichment accelerated the densification rate, and lowered coating porosity. Flowability deteriorated due to more satellite powders, but avalanche energy attained <10 mJ/kg, indicating continued re-usability. Porous coatings were deposited on Ti–6Al-4V using recycled powders, and results exhibited slightly reduced porosity, pore size, and thickness due to higher laser absorption and stronger inter-particle bonding. Nevertheless, the resulting porous structures remained within acceptable limits for biocompatibility. Heat-affected zone (HAZ) expansion was observed in recycled specimens, attributed to twin boundary formation from thermal gradients during repeated melting cycles. Overall, recycled Ti powders can be effectively utilized for fabricating porous structures, enabling sustainable and cost-effective DED for biomedical applications while maintaining acceptable coating quality and structural integrity.