Answer
A-286 (an iron-nickel-chromium based superalloy, ASTM A638) is prized for its ability to maintain high strength and oxidation resistance from cryogenic temperatures ($-423^{\circ}F$) up to $1300^{\circ}F$. Unlike some stainless steels that become brittle at cryogenic temperatures, A-286 maintains its ductility and toughness. In wave springs, this makes it ideal for liquid nitrogen or oxygen handling equipment. Its coefficient of thermal expansion is also relatively low, which helps maintain constant spring preload during the extreme thermal cycling common in rocket engine components. The processing involves an age-hardening step (typically $1325^{\circ}F$ for 16 hours) to precipitate the gamma-prime phase $(\text{Ni}_3(\text{Al, Ti}))$, which provides its strength.
