When Does Laser Powder Bed Fusion Pay Off? A Techno-Economic and Carbon Footprint Comparison with Conventional Machining for Cryogenic Electric-Pump Rotors in Ti-6Al-4V and Inconel 718

Electric-pump-fed liquid rocket engines require small, highly loaded rotors that operate in liquid methane at about 117 K and above 60,000 rpm, yet the choice between conventional manufacturing (CM) and laser powder bed fusion (L-PBF) for such parts is rarely supported by component-level data. This study compares both routes for a closed impeller in Ti-6Al-4V and Inconel 718 and for a Ti-6Al-4V inducer, using identical geometries and heat treatment. A process-based cost model, a cradle-to-gate carbon footprint and a sensitivity analysis were applied to batches of 1–36 parts. For the closed impeller, L-PBF reached cost parity with CM at a single Ti-6Al-4V part and was 44% (Ti-6Al-4V) and 65% (Inconel 718) cheaper per part at a batch of 12, because the conventional route needed two bar blanks, 6–9 h of machining and welding, and had a buy-to-fly ratio of 13. For the simpler inducer, CM remained 39–44% cheaper at all batch sizes. L-PBF reduced the carbon footprint per part by 75–83% in all cases, mainly by avoiding primary metal that is machined into chips. Geometric complexity, rather than batch size alone, therefore determines when additive manufacturing becomes the more efficient route for metallic parts operating in extreme environments.