Official Answer
Answer
A286 (ASTM A638) is an iron-base superalloy designed for applications requiring high strength and corrosion resistance up to 700 C (1300 F). For spiral retaining rings in the hot section of a jet engine, A286 is selected over 17-7PH because 17-7PH loses its strength rapidly above 350 C. A286 is solution treated and age-hardened to produce a gamma-prime [Ni3(Al, Ti)] precipitate-strengthened matrix. It maintains a high modulus of elasticity at temperature, which is critical for ensuring the ring exerts enough radial pressure to remain seated in the groove. Designers must account for the lower yield strength of A286 compared to carbon steel by increasing the ring's radial wall $b$ or thickness $t$.
