Directed energy deposition of chromium-molybdenum-vanadium cold work tool steel Vanadis 4 Extra©

Additive Manufacturing is a promising technology for the fabrication or repair of tools. However, the material portfolio is limited to materials with a decent weldability. The chromium-molybdenum-vanadium Uddeholm Vanadis® 4 Extra for Additive Manufacturing (V4E-AM) cold work tool steel is crack-free manufactured using the direct energy deposition (DED) method in this work. Process parameters are varied in a wide range to determine the influence of different build rates and cooling conditions on defect formation and resulting microstructure. Optical light microscopy proves a high relative part density above 99.5 % for different parameter combinations. Electron microscopy reveals a dendritic microstructure with a developed network of V- and Mo-rich carbides. Interdendritic cracks or cracks between colonies are not observable in the DED specimens. Nevertheless, an increase in built height results in crack formation between the substrate and the built, which imply more work on the substrate-deposit interaction and optimization of the substrate material. An increase in feed rate from 400 to 800 mm/min results in the formation of pores with diameter of 100 μm and larger. At the same time, the microstructure looks finer in the material manufactured with higher feed rate, presumably due to higher cooling rates. The hardness of the DED-specimens is around 800 to 850 HV1 while the onset for yielding exceeds 2250 MPa. The results show promising processability of the chromium-molybdenum-vanadium Uddeholm Vanadis® 4 Extra for Additive Manufacturing by DED for reparation of additive manufacturing of entire components.