Improving corrosion resistance by rising Ni-enriched Fcc phase in cupronickel alloys

This study investigates the effects of increasing fraction of Ni-enriched phase fractions on the corrosion resistance of B30 cupronickel alloys. The Calphad method was employed to analyze the influence of Fe content on the solidification process of these alloys. Results revealed that an increase in Fe content elevates the fraction of the Ni-enriched phase, a finding subsequently confirmed through microstructural characterization. Furthermore, tensile tests demonstrated that both ultimate tensile strength and yield strength were enhanced as the rising Fe content. Static immersion and electrochemical tests were also performed to evaluate the corrosion behavior. Analysis via EDS and XPS indicated that the corrosion products were primarily composed of Ni and Cu oxides, and a dense film covers the surface of Ni-enriched phase. The higher fraction of the Ni-enriched phase, induced by increased Fe content, resulting in a 12 % reduction in the average corrosion rate of B30–4Fe than B30–1Fe. With rising Fe content, the increasing fraction of Ni oxides can be considered as the other reason for improvement of corrosion resistance.