Effect of yttrium and aluminum additions on isothermal oxidation behavior of Tribaloy T-700 alloys

• The addition of Al changed the segregation of Cr element.
• Y could promote the selective oxidation of Cr.
• The selective oxidation of Al was promoted with addition of Y and Al.
• The oxidation resistance of T-700 was improved with addition of Y and Al.

The oxidation behavior of Tribaloy T-700 alloys with the additions of 0.5 wt.% yttrium, 5 wt.% Al and a combination of the two have been studied. Addition of yttrium decreased the oxidation rate and the selective oxidation of Cr was promoted. Oxidation rate also decreased with the Al addition and the selective oxidation of both Cr and Al was occurred simultaneously. The selective oxidation of Al was promoted more significantly with the addition of yttrium plus aluminum. The benefit was especially pronounced at 1000 °C, with a continuous external Al2O3 scale developed at the scale/alloy interface without any noticeable internal oxides.