Effect of Rare-Earth Ce Addition on Thermal Stability and Corrosion Resistance of Inconel 718 Superalloy

Inconel 718, which is a high-performance superalloy, is known for its strength under elevated temperatures and corrosive conditions. However, boosting the durability of this alloy in challenging industrial environments is required. Accordingly, this study investigates the effect of rare-earth Cerium (Ce) additions (0.1–0.4 weight percent (wt.%)) on the microstructure, thermal stability, and corrosion resistance of Inconel 718 superalloy synthesized via powder metallurgy. The alloys were comprehensively characterized following sintering and annealing treatment. The results demonstrate that an addition of 0.2 wt.% Ce is optimal, leading to a refined microstructure and significantly improved high-temperature thermal stability. The 0.2 wt.% Ce alloy demonstrated superior thermal stability, with a lower rate of mass gain observed at temperatures up to 1200 °C. This improvement is attributed to Ce promoting a more stable and protective surface oxide layer. Most notably, the annealed (1000 °C/2 h) 0.2 wt.% Ce alloy exhibited a dramatic enhancement in corrosion resistance, as evidenced by a corrosion current density (I_corr) of 3.690 × 10⁻⁶ A/cm², which is over an order of magnitude lower than the baseline Inconel 718. In summary, this work establishes that a minor 0.2 wt.% Ce modification is an effective strategy for substantially improving the durability of Inconel 718 for demanding applications.