Zircaloy-based materials with constant tin content, a constant sum of Fe and Cr content, and different Fe/Cr ratios were manufactured from small ingots (6 kg) by forging, β- quenching, hot rolling, and cold rolling with two different annealing sequences resulting in two accumulated annealing parameters (A-parameter A = 0.1 E-18 and A = 10 E-18 h). To study the effect of Ni, chromium was substituted by nickel in one alloy. As a reference material standard, ASTM Zry-2 was manufactured in a similar way.
These materials were examined for precipitate size by TEM and for their out-of-pile corrosion behavior in 400°C steam up to 319 days and in 500°C steam up to 24 h in a static and in a refreshed autoclave. Furthermore, samples made from these alloys were irradiated in a commercial BWR for two years.
By comparing results from different out-of-pile tests to the data from in-pile irradiation, the following conclusions can be drawn: 1. The A-parameter influence with respect to corrosion is the dominant factor for out-of-pile and in-pile corrosion behavior. 2. The (Fe+Ni)/Cr ratio influences the corrosion resistance, especially at low values below about 5. The effect is found to be strong for low A-parameter materials under irradiation of two cycles comparable to the behavior found for the high A-parameter materials in out-of-pile tests. The nodular corrosion test reproduces the in-pile behavior found for the high A-parameter materials. 3. Nickel substituted for Cr reduces the effect of the A-parameter on corrosion. 4. Sizes of intermetallic precipitates depend on chemical composition and structure. Significant numbers of Zr3Fe particles are found only at Fe/Cr ratios above 5. These particles are significantly larger than the Laves phases. 5. The influence of the chemical composition of the precipitates to the corrosion behavior cannot be finally evaluated on the two-cycle irradiated samples. Further information is expected when the samples reach higher in-pile exposure.