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Hybrid Additive Manufacturing of hot working Tool Steel H13 using Laser beam Powder Bed Fusion

: Aguirre, Jaime Cuesta
: Langer, Lukas

Augsburg, 2021, XV, 125 S.
Augsburg, Univ., Master Thesis, 2021
Master Thesis
Fraunhofer IGCV ()
additive Fertigung; Selektives Laserstrahlschmelzen

AISI H13 tool steel (X40CrMoV5-1; 1.2344) is known for its superior strength, good hardness and excellent resistance to thermal fatigue and to wear. These properties make this material an ideal candidate for high temperature applications such as molding, punches or rapid tooling. However, these applications typically require complex geometries that are challenging to manufacture by traditional production methodologies. Thus, laser powder bed fusion (LPBF) can compensate these disadvantages, through additive manufacturing. Therefore, AISI H13 components with a relative density higher than 99% were additively manufactured by LPBF process. The highest density was achieved with a volumetric energy density of 139.601 J/mm3 (245 W laser power, 650 mm/s scanning speed, 90 μm hatch spacing, 30 μm layer thickness and preheating temperature of 200 ºC). Afterwards, microstructure, hardness and tensile test have been evaluated in as-built condition and in quenched and tempered conditions: As-built microstructure showed a fine-grained martensite, with a cellular substructure consisting of retained austenite reaching microhardness of 683.3 ± 23 HV. Quenching produces a partial recovery of the solidification structure, removing the cellular substructure and reducing its microhardness to 651.38 ± 13 HV but still about 75 HV stronger than by conventional routes. Tempered martensitic structure was observed in tempered samples. Secondary hardness peak was achieved (by tempering) at 500 ºC for 4h (658.9 ± 10 HV), 45 HV higher hardness than casted and wrought H13.Additionally, hybrid additive manufacturing was performed by means of depositing AISI H13 tool steel onto 42CrMo4 and 25CrMo4 steel substrates. First, the most suitable parameter was investigated. Subsequently, an interfacial characterization of the dissimilar parts was performed through microhardness, EDX spectroscopy and optic microscopy distinguishing two different zones within the interfacial zone. The influence of heat treatments on the bonding were studied. Finally, two demonstrators were produced by LPBF, one of H13 steel and the other of H13.