Effect of Tantalum on the Microstructure and Mechanical Properties of M2 High-Speed Steel Prepared by Laser Additive Manufacturing

Herein, M2 high-speed steel (HSS) samples with different Ta contents are prepared on #45 steel substrates by a laser additive manufacturing process. The microstructure and mechanical properties of the samples are systematically studied under five different Ta contents. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analyses show that the microstructures of the samples comprise equiaxed crystals, cellular dendritic structures, and reticular eutectic carbides. The samples are mainly composed of supersaturated martensite, retained austenite, and MxCy-type carbides. The microstructures and mechanical properties of the samples are greatly affected by Ta alloying. After the M2 HSS is alloyed with 1 and 2 wt% Ta, obvious grain refinement occurs and the amount of retained austenite decreases; as a result of these microscale changes, the microhardness increases by 2.9% and 7.2%, the impact toughness increases by 12.4% and 17.4%, and the wear resistance increases by 75.74% and 25%.