Abstract:

The corrosion behavior of the new Ni-Cr-Fe base superalloy GH984G in a synthetic coal ash and flue gas environments was studied at 700 °C. The results showed that the corrosion rate was slow during the initial corrosion stage, then followed by a stage of faster mass loss. During the corrosion test, the scale trended to spall slightly, resulting in the formation of corrosion pits on the sample surfaces. The main corrosion products were identified as NiFeCrO₄ and a small amount of Cr₂O₃. The scale microstructure involved the presence of three corrosion layers. The outer layer contained Cr, Ni, Fe, O and a small amount of S. Many micro-cracks were detected in the Cr-rich intermediate oxide layer. The inner corrosion layer was thin and rich in S. Internal sulfidation and internal oxidation occurred in the substrate. Because of its relatively high Cr content, the GH984G superalloy exhibited a good corrosion resistance under the test conditions.

Key words: Ni–Fe–Cr base superalloy, Coal ash, SO2, Corrosion