Life cycle assessment on sustainable drilling of SLMed SS316L through synergetic impacts of laser scanning strategies and lubri-cooling environments

Additive manufacturing (AM) offers enhanced design flexibility, near-net-shape fabrication, and improved material efficiency, making it a viable, sustainable alternative to traditional manufacturing. However, components fabricated by AM often require extensive post-processing to meet requirements of stringent surface finish and dimensional accuracy. The significant energy and resource demand of these post-processing (especially machining), can offset the sustainability advantage of AM. Therefore, the assessment of the actual environmental impact of post-processing is one of the most important issues that have not been solved. Addressing this challenge, this study investigates the sustainability-oriented drilling of selective laser melted stainless steel 316L (SLMed SS316L), focusing on the synergetic impacts of laser scanning strategies (unidirectional, island and strip) with layer rotations (0°, 45°, and 90°), and lubri-cooling environments (dry, minimum quantity lubrication MQL, cryogenic carbon dioxide cryo-CO2, and flood). Drilling experiments were conducted at a cutting speed of 15 m/min and a feed rate of 0.06 mm/rev to evaluate machinability and environmental impacts. The result demonstrated that the Strip 45° scanning strategy with cryo-CO2 cooling delivers optimal microstructural homogeneity, superior mechanical strength (666 MPa UTS), minimal tool wear (85%), reduced thrust forces (40%), lower energy consumption (40%), and enhanced hole quality, compared to dry cutting conditions. Furthermore, to quantitatively assess environmental impacts, a cradle-to-gate life cycle assessment (LCA) was performed on the best-performing specimens (one specimen was chosen from each scanning strategy at 45°) using the ReCiPe 2016 midpoint (H) method. The LCA conclusively validated the environmental superiority of the advanced cooling techniques, with cryogenic CO2 cooling achieving an average reduction of 42.3% across key impact categories. These findings indicate that, under the investigated drilling conditions, the strip 45° scanning strategy combined with cryo-CO2 cooling provides the most favorable balance between machining performance and environmental sustainability for SLMed SS316L.