Oxidation Behavior of a Single-Crystal Ni-base Superalloy in Air at 900, 1000 and 1100°C

Abstract

The isothermal-oxidation behavior of a single-crystal (SC) Ni-base superalloy was studied over the temperature range from 900 to 1100°C and analyzed by OM, TGA, XRD, EDX, SEM and EPMA. The alloy obeyed a subparabolic rate law during oxidation at 900 and 1000°C, whereas the alloy showed parabolic behavior at 1100°C exposure. The variations in the chemical composition due to segregation, which resulted from the solidification process, led to the formation of different kinds of oxide scale on the dendritic and interdendritic areas during oxidation at 900 and 1000°C, while the alloy exhibited relatively uniform oxidation at 1100°C. The growth mechanism of the scale is discussed.

Oxidation Behavior of a Cast Polycrystalline Ni-Base Superalloy in Air: At 900 and 1000 °C

“…Compared to values for pure Ni found in the literature [18,19], the K p value is less one or two order of magnitude than these reported as 1.0 · 10 À5 to 4 · 10 À6 (mg 2 /cm 4 )/s. It can be predicted that the alloy has much lower parabolic rate constants due mainly to the formation of an Al-rich, slow-growing protective layer on the alloy surface.…”

An oxidation resistant refractory high entropy alloy protected by CrTaO4-based oxide

“…In present study, since no obvious trace of TiN was found within Si-bearing Cr- rich phase, it is reasonable to assume that nitrogen preferentially diffused through Mo-rich dendrites and formed TiN particles, while interdendritic regions were less affected by nitrogen. In previous study on the oxidation of Ni- base superalloys, TiN could be found beneath the internal oxidation layer 24–26 , and the solubility and diffusion of nitrogen was reported to increase with increasing Cr content in Ni-Cr-Al-Ti superalloy without Si addition 25 . Therefore, both Cr and Si content might be important for providing nitridation resistance.…”

Kinetic oxidation model including the transient regime for a single crystal nickel-based superalloy over the temperature range 750–1300 °C

“…EDS analyses (not shown) show that these precipitates are rich in titanium. This type of precipitate is likely titanium nitrides which would have formed by internal nitridation during the first hours before the oxide layer is sufficiently protective to prevent the diffusion of nitrogen inwards, as already shown for the oxidation of Ni-base single crystal alloy [35].…”