Effect of Sc and Gd co-doping on the oxidation behavior of FeCrAl alloys in water vapor environment at 1000°C

Abstract

Rare earth Sc, Gd double doped alloys FeCrAl-xScxGd with different compositions (x=0.25, 0.5, 1.0, 2.0) were prepared by vacuum hot press sintering, and their microstructures were investigated. The double-doped alloy FeCrAl-xScxGd was also oxidized with the single-doped alloys FeCrAl-xSc and FeCrAl-xGd (as a control variable) at high temperature water vapor oxidation at 1000 ℃ for 100 h, and the oxidation kinetic curves were investigated. It is concluded that they have positive effects on the enhancement of the oxidation resistance of FeCrAl alloys in different aspects, while there is no "synergistic effect" of Sc and Gd rare earth elements on the oxidation kinetics of FeCrAl alloys. In FeCrAl alloys, the element Gd not only exists as Gd monomer, but also forms two intermetallic compounds of Gd and Fe, Fe5Gd and Fe9Gd, and the oxide Gd3Fe2Al3O12, which hinders the outward diffusion of Al and reduces its oxidation rate. The element Sc, on the other hand, undergoes longitudinal segregation at the oxide grain boundaries and produces a pinning effect on the alumina scale, which enhances the bonding at the oxide scale/alloy interface, thus preventing the growth of new oxide grains and the generation of new nucleation sites at the alumina scale/alloy interface, thus having a positive effect on the alloy.