Hot-corrosion resistance of Ni-Cr-Al-Y and Ni-18% Si alloys in sulfate eutectic and sulfate plus vanadate melts at 973 K

The hot-corrosion resistance of Ni-Cr-Al-Y and Ni-17.8 wt.% Si was examined in sulfate and sulfate plus vanadate melts at 973 K. Two salt-deposit compositions were considered: (a) sodium sulfate 50 mole% magnesium-sulfate eutectic and (b) sodium sulfate plus 20 mole% sodium meta-vanadate. Both types of deposit were molten at the test temperature. Cyclic hot-corrosion tests were conducted in a gas mixture consisting of oxygen, sulfur dioxide, and 0.0240 vol.% sulfur trioxide. The hot-corrosion kinetics were evaluated using weight change and the corrosion mechanism deduced from post-test metallography. The results indicate that the nickel-silicon alloy had much better hot corrosion resistance than Ni-Cr-Al-Y under all test conditions considered. The sample preparation process is outlined, the test procedure summarized, and the experimental results are presented and discussed.