Enhanced Oxidation Resistance of Pt-Containing Inconel 718 Alloy through Facilitated Formation of Protective Chromia

Abstract

This study investigates the influence of Pt addition on the oxidation behavior of a Cr₂O₃-forming superalloy. Inconel 718 (IN718) alloys with varying Pt content were prepared and subjected to isothermal oxidation tests. The results demonstrate that Pt significantly enhances the oxidation resistance of IN718, as evidenced by reduced weight gain, thinner oxide layers, and smaller oxide particles. Pt addition also increases the activation energy for both initial interface oxidation and ion diffusion during long-term oxidation. Furthermore, Pt promotes the formation of a Cr₂O₃ layer while suppressing the formation of other undesirable oxides, resulting in a more cohesive and stable oxide layer. The improved oxidation resistance is attributed to two key factors: during the initial oxidation stage, Pt, as a noble element, reduces the activity of the primary oxide-forming element Cr to oxidative environments, thereby lowering its susceptibility to initial oxidation at the metal–oxidant interface. During long-term oxidation, Pt preferentially substitutes for Ni in major phases such as γ-Ni(Cr,Fe) and γ′-Ni₃(Al,Ti), locally increasing the Cr composition. This promotes Cr oxidation, effectively suppressing the oxidation of Ni or Fe. These findings suggest that Pt addition is a promising approach for enhancing oxidation resistance in alloy design.