Effect of Superficially Applied Y_2O_3 Coating on High-Temperature Corrosion Behavior of Ni-Base Superalloys

摘要

Inhibitors and oxide additives have been investigated with varying success to control high-temperature corrosion. Effect of Y_2O_3 on high-temperature corrosion of Superni 718 and Superni 601 superalloys was investigated in the Na_2SO_4-60 pct V_2O_5 environment at 1173 K (900 °C) for 50 cycles. Y_2O_3 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 Na_2SO_4-60 pct V_2O_5 environment. The Y_2O_3 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 YVO_4 phase. There was a distinct presence of a protective Cr_2O_3-rich layer just above the substrate/scale interface in the alloy. Whereas Cr_2O_3 was present with Fe and Ni in the scale of Superni 718. Y_2O_3 seemed to be contributing to better adhesion of the scale, as comparatively lesser spalling was noticed in the presence of Y_2O_3.