STUDIES ON THE HOT CORROSION OF SOME NICKEL-BASE SUPERALLOYS BY VANADIUM PENTOXIDE

The hot corrosion attack of Nickel-base superalloy samples of Nimonic 80A, Hastealloy C-276 and Superni-600 coated with different amounts of V2O5 was studied by the weight change measurement for a period of 100 hours at 923,973 and 1023 K in air. The corrosion products of the scales obtained were anlysed by X-ray diffraction. Results show that the hot corrosion kinetics obeys a parabolic law with two regions at 973 and 1023 K, the corrosion rate falling with the formation of a solid Ni3V2O8 layer. This is explained in terms of the acid-base fluxing mechanism and a second mechanism by which nickel vanadate is precipitated from a nickel vanadium compound located in the short circuit diffusion path assumed to be present in the growing oxide.