Official Answer
Answer
SAE 1070 carbon steel is unsuitable for exhaust systems because its mechanical properties degrade rapidly above $250^{\circ}F$, and it lacks oxidation resistance. A286 is an iron-base superalloy (UNS S66286) designed for continuous service up to $1300^{\circ}F$. A286 provides high tensile strength and maintains a stable modulus of elasticity at elevated temperatures. Unlike carbon steel, A286 is precipitation-hardenable (solution treated and aged) to achieve a hardness of 35-42 HRC. In exhaust environments, A286 forms a protective oxide layer that prevents further corrosion. For designers, using A286 means the thrust capacity calculated at room temperature will remain relatively consistent during the thermal cycles of the engine operation.
