Laser beam direct energy deposition coatings of blended high–carbon particles originating from recycled electro discharge machining waste of a H11 alloy

This study investigated powder mixtures composed of recycled eroded particles (REP) from electro discharge machining (EDM) and H11 powder, with a focus on their use in laser beam direct energy deposition. The compositions of H11 and REP are close, with difference being their carbon content due to an uptake during EDM. Mixtures with varying carbon contents were created to minimize crack formation, and analyzed for particle size distribution, chemistry and usability for coatings. By this, a secondary powder supply is ensured. Powders were deposited on a low–carbon substrate, and layers evaluated through image analysis and hardness testing. Thermal analyses were performed to investigate microstructural transformations. Metallographic investigations were employed to study the microstructure. The deposition resulted in crack–free layers on preheated substrates, with targeted dilution ratios ranging from 10 to 24 %. Developed microstructures were complex, exhibiting phases as M 7 C 3 carbide, M 3 C carbide, martensite, and austenite. Carbon loss and phase transformations were observed and could be controlled by adjusting the feed material mixture (0 %, 15 %, 30 %, 45 %, 60 %, 100 % REP). Hardness testing showed that pure H11 layers have lower microhardness (660 HV10) compared to pure REP layers (790 HV10), with the hardness of coatings varying based on REP content and present phases (365–510 HV10). Thermal analysis confirmed the presence of observed phases, and electron backscatter diffraction proved austenite and martensite along with carbide precipitates, further elucidating the complexity of material systems. • Eroded particles of high carbon content successfully used in direct energy deposition. • Tunable microstructures by application of powder mixtures with H11 alloy • Hard coatings deposited on substrates with variable hardness. • Thermal and metallographic investigations revealed complex material behavior.