Microstructure and surface characterization of a selectively dissolved Ni-Ni3Si eutectic alloy

摘要

A novel channeled Ni3Si surface was fabricated from directionally solidified Ni-Ni3Si eutectic alloy by selective phase dissolution. A combined process of the polarization curve and the potential-pH diagram was applied to analyze the selective dissolution process. The alpha-Ni phase of the eutectic alloy was successfully removed at 1.34 VsHE and 1.67 V-SHE. XPS analyses showed that the oxide film produced after selective dissolution was mainly composed of SiO2 and Ni(OH)(2), with SiO2 as the main component. This finding indicated that SiO2 retarded the dissolution of Ni3Si phase and was preferentially formed on 13-Ni3Si phase, resulting in successful selective dissolution. The optimum potential for selective dissolution of the a-phase was at 1.34 V-SHE, at which more SiO2 molecules were formed.