Characterization of Ni61.0Nb35.5B3.0Si0.5 Alloy in Fully Amorphous and Partially Crystallized Conditions

Abstract

Nickel-based alloys with polycrystalline structure are known for their high corrosion resistance and good mechanical strength. Moreover, the possibility of amorphization of nickel-based alloys could improve both properties. In this work, the new Ni61.0Nb35.5B3.0Si0.5 alloy was processed by melt-spinning and conformation spray to produce amorphous materials. Subsequently, the as-cast samples were heat-treated to result in partial crystalline fractions. The structures were characterized by x-ray diffraction (DRX), differential scanning calorimetry (DSC), light optical (LOM) and scanning electron microscopy (SEM). The polarization curves of all structural conditions obtained in 3.5% NaCl aqueous solution at 25 C indicated the positive effect of amorphous phase in corrosion tests. Indeed, all studied conditions produced a large passivation potential range, even with partial crystalline presence. Furthermore, the measured passivation current density was proportional to crystalline content revealing the important effect of amorphization in the corrosion resistance of the present nickel alloy.