Official Answer
Answer
Inconel X-750 (AMS 5698) is a nickel-chromium precipitation-hardened alloy specifically chosen for its high-temperature strength and relaxation resistance. While 302 Stainless Steel loses significant load-bearing capacity above $250^{\circ}C$ due to creep, Inconel X-750 maintains its mechanical properties up to $700^{\circ}C$. The material undergoes a solution treatment followed by age hardening to precipitate the $\gamma'$ phase, which pins dislocations and prevents plastic flow. In gas turbines, the spring's relaxation (loss of load over time) is critical; X-750 exhibits less than $5\%$ relaxation at $540^{\circ}C$ under high stress, whereas 302 or even 17-7PH would fail prematurely due to thermal softening.
