New Fe-Cr-Mo-(Nb, Ta)-C-B glassy alloys with high glass-forming ability and good corrosion resistance

New Fe-based glassy alloys of Fe₄₅Cr₁₆Mo₁₆C₁₈B₅, Fe₄₅Cr₁₆Mo₁₄Nb₂C¹⁸ B₅ and Fe₄₅Cr₁₆Mo₁₄Ta₂C₁₈ B₅ were synthesized. They exhibit a large supercooled liquid region (ΔT_x) reaching 58 K before crystallization and high reduced glass transition temperatures (T_g/T_m) up to 0.62. These values indicate that these Fe-based alloys have a glass-forming ability which is high enough to enable the formation of bulk glassy alloys. The Fe-based glassy alloys have high corrosion resistance in 1, 6 and 12 mol·L^-1 HCl solutions at room temperature. The corrosion rates are in the range of 10^-4-10^-2 mm·y^-1. The glassy alloys are spontaneously passivated in 1 and 6 mol·L^-1 HCl solutions with wide passive region and low passive current density in the range of 10^-2-10⁰ A·m^-2. No pitting corrosion is seen even in 12 mol·L^-1 HCl solution. The addition of Nb or Ta to the glassy alloys is effective on enhancing the corrosion resistance.