High Temperature Scaling of Monophase Nickel-Titanium Alloys

Abstract

Abstract The oxidation of Ni-rich nickel-titanium solid solutions has been studied in the 950 to 1250 C range. Titanium additions decrease the oxidation resistance of nickel to an extent depending on the Ti content and temperature. Essentially monophase NiO scales are formed on a dilute alloy (1.60 Wt% Ti), with a small concentration of dissolved titanium and few isolated particles of NiTiO3. At higher titanium concentrations (7.64 Wt% Ti), the scale contains NiO in the outer region and TiO2 or NiTiO3 in the inner part. After a long oxidation time, NiO begins to grow also at the scale surface beneath the Ti-rich layer, due to a strong Ti depletion of the alloy matrix. Extensive internal oxidation is also observed under any condition.