Answer
$17-7PH$ (AISI 631) in the CH900 condition offers a superior combination of high strength and corrosion resistance compared to $302$ Stainless Steel. $17-7PH$ undergoes a precipitation hardening process (Condition C to CH900) which yields a tensile strength up to $240$ ksi. This allows for higher stress levels ($σ_{all} \approx 0.75 \cdot σ_{uts}$) and a smaller footprint for the same load. Additionally, $17-7PH$ exhibits better relaxation resistance at temperatures up to $650^{∘}F$ ($343^{∘}C$). In contrast, $302$ Stainless Steel, while cheaper and highly ductile, is limited to approximately $550^{∘}F$ ($288^{∘}C$) and has lower fatigue limits. For mission-critical aerospace components, the phase transformation in $17-7PH$ provides the dimensional stability required for tight-tolerance wave spring applications.
