The Study On The Corrosion Behavior Of Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂ Bulk Amorphous Alloys

bulk amorphous alloys with diameter of 5mm were prepared by copper mold suction casting method. The amorphous structure was confirmed by X-ray diffraction (XRD), the thermodynamic parameters were measured by differential thermal analyses (DTA). The corrosion resistance of Fe-based amorphous alloys in different aggressive solutions was studied by immersion and electrochemical measurement technology, and the results were analyzed.Immersion experiment shows that Fe41Co7Cr15Mo14C15B6Y2 amorphous alloys have excellent corrosion-resistant in different aggressive solutions. After immersion in lmol/L HCl, lmol/L H2SO4, 1mol/L HNO3, 1mol/L NaOH and 3.5% NaCl solutions for two weeks, pitting takes place in all of the Fe41Co7Cr15Mo14C15B6Y2 amorphous alloys surface. Observing by SEM, we found that Fe-based amorphous alloy has the least pitting holes in 3.5% NaCl solution, followed by acid solutions whose concentrations are 1 mol/L, pitting in 1mol/L NaOH is more serious than in other solutions. It shows that Fe-based BMG has the best corrosion-resistant behavior in 3.5% NaCl solution, followed by acid solutions with the concentration of 1 mol/L, the corrosion resistance is worse in 1 mol/L NaOH solution. The reason is that the extent to the rapid formation of passive films on amorphous alloys surface in different aggressive solutions is different, and the composition of the films is different.Electrochemical measurements reveal that Fe41Co7Cr15Mo14C15B6Y2 amorphous alloys have prominent corrosion resistance in acid solutions. In lmol/L HCl solution and 1 mol/L H2SO4 solution, the corrosion resistance of Fe-based BMG is superior to stainless steel, and almost the same with Ti6A14V. As the concentrations of acid solutions increase, the corrosion resistance of Fe41Co7Cr15Mo14C15B6Y2 amorphous alloys decreases. The result of XPS shows that the passive films of Fe-based BMG formed in HCl solution are mainly composed by the inner MoO2 film, the middle Cr(OH)3 and Fe(OH)3 films, and the outer CrO42- and MoO42- negative ions. The result of linear energy spectrum shows that the pitting corrosion on alloys surface is caused by the transpassive dissolution of Mo in the passive film.Fe41Co7Cr15Mo14C15B6Y2 amorphous alloys have excellent corrosion resistance in NaCl solutions. The corrosion resistance of Fe-based amorphous alloy in 3.5% NaCl solution is superior to stainless steel but inferior to Ti6A14V. This conclusion is confirmed by the salt spray experiment. The reason is relevant to the plenty of Cr and Mo in Fe-based amorphous alloy.The corrosion behavior of Fe41Co7Cr15Mo14C15B6Y2 amorphous alloys in NaOH solution is worse. The corrosion resistance of Fe-based amorphous alloy in 1 mol/L NaOH solution is lower than stainless steel and Ti6A14V. The reason is that Cr and Mo in amorphous alloys dissolve in alkali solutions. As the concentrations of NaOH solution rise, the corrosion-resistant of Fe-based amorphous alloy declines.