Abstract:
Inhibitors and oxide additives have been investigated with varying success to control
high-temperature corrosion. Effect of Y2O3 on high-temperature corrosion of Superni 718 and
Superni 601 superalloys was investigated in the Na2SO4-60 pct V2O5 environment at 1173 K
(900 C) for 50 cycles. Y2O3 was applied as a coating on the surfaces of the specimens. Superni
601 was found to have better corrosion resistance in comparison with Superni 718 in the
Na2SO4-60 pct V2O5 environment. The Y2O3 superficial coating was successful in decreasing the
reaction rate for both the superalloys. In the oxide scale of the alloy Superni 601, Y and V were
observed to coexist, thereby indicating the formation of a protective YVO4 phase. There was a
distinct presence of a protective Cr2O3-rich layer just above the substrate/scale interface in the
alloy. Whereas Cr2O3 was present with Fe and Ni in the scale of Superni 718. Y2O3 seemed to be
contributing to better adhesion of the scale, as comparatively lesser spalling was noticed in the
presence of Y2O3.
