Life-Cycle Assessment of a Hybrid HS-DED Manufacturing Route for Punching Dies with MMC Coatings

Abstract Amid tightening CO 2 pricing and climate targets, hybrid repair chains that combine additive manufacturing with conventional processes are explored to extend tool life and cut the environmental footprint of metal working. This study presents a cradle-to-grave life-cycle assessment (LCA) of a high-speed directed energy deposition (HS-DED) repair route for punching dies, benchmarked against a conventional powder metallurgy (PM) route. Two metal matrix composite (MMC) coatings using DIN 1.2888 tool steel as matrix material, WC-MMC and TiC-MMC, were deposited on DIN 1.2379 tool steel substrates. Comparing service lives of the punches of 330,000 strokes (WC-MMC), 164,000 strokes (TiC-MMC), and 200,000 strokes (PM) with the ReCiPe 2016 midpoint method, WC-MMC achieved the lowest global warming product (GWP) (0.93 kg CO 2 -eq), a 48% reduction versus PM (1.79 kg CO 2 -eq), and outperformed TiC-MMC (3.94 kg CO 2 -eq). Scenario analysis showed further GWP drops up to 78% with ten recoating cycles, 5-7% with reduced argon or nitrogen substitution, and over 80% with a renewable electricity mix. WC-MMC is consistently superior across 17 of 18 impact categories, driven by its long tool life and substrate reuse. The results show that HS-DED-based hybrid manufacturing, especially WC-reinforced MMCs with a repair option, can lower the carbon footprint of punching dies in sheet metal fabrication.