Study of microstructure and corrosion resistance of FeCrAl-Gd alloys

The corrosion resistance of Fe-21Cr-4Al alloys with different gadolinium (Gd) contents was investigated by means of microstructure, salt spray corrosion and electrochemical tests. The microstructural analysis shows that Gd and Gd2O3 formed at grain boundaries will pinch the grain boundaries and slow down the grain growth, thus reducing the grain size. The corrosion results showed that as with the increase of the Gd component, there are two competing corrosion mechanisms: 1) the grain size becomes smaller, which makes the corrosion pit difficult to expand; more Gd oxides are formed, which hinders the penetration of Cl; 2) the number of grain boundaries and dislocations increases, which expedite the corrosion rate; and the increasing Gd-rich phase serve as cathodes for the micro-galvanic corrosion. A minimum corrosion rate of 1.94 mm/year was achieved for the Gd-containing alloy, a reduction of 46.4% compared to the original alloy.