Corrosion Behavior of Zr-Nb-Cu Alloys in 500℃/10.3MPa Steam

Abstract:

The corrosion behavior of Zr-Nb-Cu alloys in 500 ℃/10.3 MPa superheated steam were investigated in the present work. Severe non-uniform corrosion was occured in Zr-Nb-Cu alloys with low content of Nb or Cu elements, while Zr-0.2Nb-0.2Cu and Zr-0.2Nb-1.0Cu alloys demonstrated relative good corrosion resistance. It was found that the non-uniform corrosion behavior has been fully inhibited in Zr-0.2Nb-0.2Cu alloy, and further increase of amount of Cu element showed slight effect on the corrosion resistant behavior. The microstructure of zirconium alloys (especially the micro-pores, micro-cracks) is strongly related to the oxidation of alloying elements and precipitates. The presence of Nb in zirconium alloys would delay the oxidation of Zr₂Cu phase and the corresponding diffusion of the oxidation products. Moreover, Nb element could also inhabit the formation of the cracks in the oxide film and the delay the transformation from columnar to equiaxed crystal morphology. Therefore, the addition of Nb element could improve the corrosion resistance of the zirconium alloys containing Cu elements.

Key words:zirconium alloys; Nb; Cu; corrosion behavior