Microstructure of Deposited AISI M4 High Speed Steel On AISI D2 Tool Steel Substrate Using L-DED Process

Microstructures of a single layer AISI M4 high speed steel deposited on a AISI D2 tool steel substrate using the L‑DED process with two levels of global energy density were characterized and compared.

A five-axes PRECO-SL 8600 CNC machine was used to deposit the M4 powder feedstock with a continuous wave laser source, near-infrared wavelength laser beam, 2.0 mm spot size, and coaxial continuous feed nozzle. The M4 powder had particle sizes between 60 and 210 μm and a volumetric mean diameter of 119 µm. The quenched and tempered D2 substrate had a thickness of 15 mm and a hardness of with 755 HV. Two laser power/scan speed sets were used: 700 W/800 mm/min and 1100 W/500 mm/min, that is GED = 26.3 J/mm² and GED = 66 J/mm², respectively.

The microstructures were characterized through optical micrography, SEM and EDS, and WDS microanalyses. Five different zones could be distinguished, according to their microstructure features, and differences related to the energy density were analyzed.