EFFECT OF Cu CONTENT ON THE CORROSION RESISTANCE OF Zr-0.80Sn-0.34Nb-0.39Fe-0.10Cr-xCu ALLOY IN SUPERHEATED STEAM AT 500 °C

The effect of Cu content on the corrosion resistance of Zr-0.8Sn-0.34Nb-0.39Fe-0.1Cr-xCu alloys (x = 0.05-0.5, mass fraction, %) was investigated in superheated steam at 500 degrees C and 10.3 MPa by autoclave tests. The microstructures of the alloys are observed by TEM. The results show that (0.05-0.5)Cu addition has little effect on the corrosion resistance of the alloys. When x is below 0.2, the precipitates Zr(Fe, Cr, Nb)(2) with hcp structure and Zr3Fe containing Cu with orthorhombic structure are detected. When x is above 0.2, besides Zr(Fe, Cr, Nb)(2) and Zr3Fe containing Cu, the precipitate of Zr2Cu with tetragonal structure is also detected. Zr(Fe, Cr, Nb)(2) precipitates are smaller than the precipitates containing Cu in size. The precipitates containing Cu are found in the alloy even with 0.05Cu, indicating that the Cu content in alpha-Zr matrix is very small. Therefore, the reason that the Cu content has little effect on the corrosion resistance of the alloys is maybe related to the lower Cu content in alpha-Zr matrix.