Transition from internal to external oxidation in binary Ni–Zr and ternary Ni–Zr–Y alloys

• Y and Zr are used as alloying elements in Ni.
• Ni–Zr and Ni–Zr–Y show transition from internal to external oxidation.
• Oxide phase leads to enhanced oxygen diffusion.

In the present work the transition from internal to external oxidation is investigated in binary Ni–Zr and ternary Ni–Zr–Y alloys in terms of the Zr and Zr + Y content respectively. In both systems a transition was found, but only in ternary alloys this transition leads to a significant drop of the oxidation rates. As proposed by the theory of Wagner this is attributed to the formation of a dense oxide layer.