A New Oxide Morphology Map: Initial Oxidation Behavior of Ni-Base Single-Crystal Superalloys

Abstract

Predictions for oxidation behavior of Ni-base superalloys become more difficult than before because of the complex alloy composition. In this study, we focus on the initial oxidation behavior of Ni-base superalloys, and we suggest a new diagram to predict the initial oxide morphology of Ni-base superalloys with 63 binary, ternary, and multicomponent Ni-base single-crystal superalloys at 1373 K (1100°C). As a comparison of observed and calculated weight changes after one cycle at 1373 K (1100°C) obtained by a regression analysis, 63 alloys demonstrated two distinct behaviors, which are divided heretofore into group A and group B. Microstructural observation revealed that an oxide layer in the group A alloys consists of Al 2 O 3 and/or spinel or complex oxide, whereas an oxide layer in the group B alloys consists of a thick NiO layer with an Al 2 O 3 internal subscale. Thermodynamic properties can reflect more effects of alloy elements in Ni-base superalloys, and Al and Cr activities, calculated by Thermo-Calc, were used as factors to predict initial oxidation morphology. Groups A and B alloys can clearly be divided according to Al and Cr activities. This was suggested as a new diagram to predict the initial oxide morphology of Ni-base superalloys, and possibly it can apply for any generation of Ni-base superalloys.

High Temperature Oxidation and Corrosion Properties of High Entropy Superalloys

“…The 30 min test results show that gradual internal oxidation occurs in HESA-1, while the Al2O3 formation in HESA-2 becomes more continuous. According to the literature, the Al concentration in conventional Ni-based superalloys is usually maintained at 5-6 wt.% to promote continuous Al2O3 formation [10,[37][38][39]. By contrast, HESA-1 only contains 3.9 wt.% of Al, and it does not form continuous Al2O3, though its Al activity is the highest among the three alloys.…”

Development of strong, oxidation and corrosion resistant nickel-based superalloys: critical review of challenges, progress and prospects

“…Modelling attempts made by Bench et al [55], Sato et al [56]. and Suzuki et al [57] are in early stages of development. This is due to lack of reliable thermodynamic and kinetic data for the mixed oxides that form concurrently with alumina during oxidation.…”

Prediction of Initial Oxidation Behavior of Ni‐Base Single Crystal Superalloys: A New Oxidation Map and Regression Analysis

“…In this study, we focus on two points concerning the initial oxidation behavior of Ni-base single crystal superalloys: establishing empirical equations for predicting the initial oxidation behavior based on weight change measurements, and suggesting an approach to determine the nature of initial oxides by means of thermodynamic properties [11,12]. Specifically, cyclic oxidation test results of 70 binary, ternary, and multicomponent Ni-base superalloys were used to draw the new oxidation map to distinguish the type of oxides in Ni-base single crystal superalloys.…”