HWTS 50 Tool Steel Tailored for Laser Powder Bed Fusion: Sliding Wear of Bare Surfaces and Nitriding Response in Comparison with 18Ni300 and AISI H13

This study examines the properties and performance of Osprey HWTS 50, a lean hot work tool steel with 0.22 mass% carbon, manufactured via laser powder bed fusion (PBF-LB/M). Its performance in sliding wear and gas nitriding tests is compared with wrought AISI-H13 and H11 (≈0.4 mass% carbon), as well as to PBF-LB/M-processed maraging steel (18Ni300). HWTS 50 is tested in three conditions: as-built (AB), directly double-tempered (DT, ≈50 HRC), and quenched and tempered (QT, ≈50 HRC). Results suggest that HWTS 50 variants exhibit comparable or slightly improved sliding wear resistance compared to wrought H13, outperforming the carbon-free 18Ni300 (≈54 HRC). Gas nitriding increases surface hardness in HWTS 50 to levels similar to wrought steels, but the nitriding hardness depth (NHD) is significantly greater. The deeper NHD is attributed to HWTS 50's lower chromium (≈3 mass%) and vanadium (≈0.5 mass%) contents, which enhance nitrogen diffusion and the high dislocation density from the PBF-LB/M process. Microscopical investigations show HWTS 50 develops a thicker compound layer (≈8 μm vs. ≈3 μm in wrought H13 and H11) and diffusion depth. XRD analysis confirms comparable nitride phases (i.e., Fe2-3N and Fe4N) form in the NHD across all materials.