Comparative Analysis of Inconel 718 and Inconel 625 for Rocket Nozzles: Performance, Durability, and Manufacturing Influence

Rocket nozzles operate under extreme thermal loads, high-velocity gas flow, and mechanical stresses, making material selection crucial for performance and durability. Inconel 718 and Inconel 625 are widely used nickel-based superalloys due to their high temperature strength, oxidations resistance, and mechanical reliability. However, a direct comparison of their erosion resistance, thermal stability, and manufacturability for rocket nozzle applications remains limited. This review consolidates research on their microstructural behavior, welding characteristics, and additive manufacturing feasibility to assess their suitability for propulsion systems. While Inconel 718 offers superior strength, creep resistance, and phase stability, Inconel 625 provides better flexibility, oxidation resistance, and weldability. Additionally, the influence of fabrication techniques, phase transformations, and structural integrity on long-term performance is examined. The findings provide valuable insights into performance trade-offs and material selection strategies, supporting advancements in rocket nozzle design and manufacturing for next-generation aerospace applications.