Official Answer
Answer
17-7PH (ASTM A693) in Condition CH900 offers superior yield strength ($S_y \approx 1170-1310$ MPa) and fatigue resistance compared to 302 Stainless Steel. The CH900 process involves cold reduction followed by precipitation hardening at $482^\circ C$ ($900^\circ F$), which creates a martensitic structure with fine precipitates. This allows for higher operating stresses and lower relaxation at temperatures up to $343^\circ C$. In contrast, 302 SS relies solely on cold working for strength and is limited to lower temperatures ($< 288^\circ C$) and lower stress levels before permanent set occurs via the relation $\tau = \frac{8PD_m}{\pi t^3}$ exceeding the elastic limit.
