Improvement of the oxidation resistance of Tribaloy T-800 alloy by the additions of yttrium and aluminium

The microstructures and oxidation behaviour of the modified Tribaloy T-800 alloys by additions of yttrium and yttrium plus aluminium have been studied. At the presence of yttrium alone, the oxidation rate decreased, and the selective oxidation of chromium was promoted, which was related to the refinement of alloy phase size. The addition of yttrium plus aluminium further reduced the oxidation rate. The selective oxidation of chromium and aluminium were both promoted significantly. The benefits were especially pronounced at 1000 °C, with the formation of protective alumina external layer and no internal oxides, which may be detrimental to the alloy mechanical property.

Research highlights
► The additions of yttrium (Y) reduced the oxidation rate of Tribaloy T-800 alloy.
► Y promoted selective oxidation of Cr due to refinement of alloy phase size.
► The oxidation rate was further reduced by Y plus Al with a protective Al2O3 scale.
► The positive effect of Y and Al being more pronounced at the higher temperature.