Corrosion resistance of M2 high-speed steels fabricated by electron beam powder bed fusion

As the high-carbon and high-alloy steels, the M2 high-speed steels (HSS) are widely used in cutting tool applications. Under the extreme conditions (high-speed cutting), the surface of high-speed steels interacts with the coolant in thermal-chemical interaction, leading to the corrosion-wear coupling failure. The M2 high-speed steels were fabricated by electron beam powder bed fusion (EB-PBF) in this paper. The effects of input energy density (VED) on relative density, microstructure, and corrosion behavior were systematically investigated, the comparative analysis was conducted on the corrosion resistance between EB-PBF fabricated and wrought M2 HSS in 3.5% NaCl solution (mass fraction). In the results, the EB-PBF fabricated M2 HSS exhibits the refined grain size (5~8 μm) with homogeneously dispersed carbides (<2 μm) in near-spherical or short rod-like morphologies; notably, the coarse primary carbides commonly observed in wrought M2 HSS are absent. At the optimal VED of 43.3 J·mm⁻³, the EB-PBF fabricated M2 HSS achieves the peak relative density (99.8%), and the corrosion current density and charge transfer resistance in 3.5% NaCl solution are 71.3% and 123.7% of those of wrought M2 HSS, respectively, demonstrating the significant enhanced corrosion resistance.