Bulk glassy Fe-Cr-Mo-C-B alloys with high corrosion resistance

The preparation of bulk glassy alloys with high glass-forming ability and high corrosion resistance in Fe-based system was succeeded by means of copper-mold casting. The temperature interval of supercooled liquid region (ΔT_x) is as large as 53-62 K and the reduced glass transition temperature (T_g/T_m) is as high as 0.62-0.63 for the cast Fe_50−xCr₁₆Mo₁₆C₁₈B_x (x=4, 6, 8 at.%) glassy alloys. The corrosion rates of the Fe_50−xCr₁₆Mo₁₆C₁₈B_x glassy alloys with a diameter of 1.2 mm were in the range of 10⁻³-10⁻² mm year⁻¹ in 1, 6 and 12 N HCl solutions at 298 K. The bulk glassy alloys are spontaneously passivated in 1 and 6 N HCl solutions with wide passive region and low passive current density. They do not suffer pitting corrosion even when polarized anodicly in 12 N HCl solution up to 1.0 V (Ag/AgCl). The high corrosion resistance is due to the formation of chromium-rich passive films during immersion in HCl solutions. In addition, the increase of boron content in alloys improves the corrosion resistance of the bulk glassy alloys within the composition range examined.