Official Answer
Answer
A286 (ASTM A638) is an iron-base superalloy that maintains high strength and oxidation resistance up to $700^∘C$. For retaining rings in turbines, it is superior to stainless steels because it does not lose its 'spring temper' at operating temperatures. The material is precipitation-hardened to achieve a yield strength of approximately 700-1000 MPa. Its coefficient of thermal expansion is also closely matched to many nickel-based turbine alloys, which minimizes the risk of the ring losing its grip due to differential thermal expansion. Processing involves solution treating at $980^∘C$ followed by aging at $720^∘C$ for 16 hours to precipitate the $\gamma'$ phase.
