Oxidation Rate and Oxide Microstructures of Zr-1Nb-xFe-0.05Cu-0.05Ge Alloys Corroded in 400 °C Superheated Steam

The oxidation rate and the oxide film microstructures of Zr-1Nb- x Fe-0.05Cu-0.05Ge alloys ( x = 0.1, 0.15, 0.25, 0.35, wt%) corroded in superheated steam at 400 °C/10.3 MPa were investigated. Results show that the Zr-1Nb-0.35Fe-0.05Cu-0.05Ge alloy possesses the best corrosion resistance. As the content of Fe increases, the corrosion resistance of alloys is improved significantly and the main SPPs change from hcp-Zr(NbFe) 2 SPPs to a mixture of hcp-Zr(NbFe) 2 and fcc-Zr(NbFe) 2 SPPs. Fe delays the development of the defects which lead to the formation of micro-cracks finallyin oxide film. It also defers the evolution from columnar grains to equiaxed grains in the oxide film. [Zr-Nb-Fe]-type SPPs are initially oxidized into amorphous phases to reduce the grain boundary stress, which can delay the transformation of oxide film microstructure.