Answer
17-7PH CH900 (Condition C, precipitation hardened to 900°F) is a semi-austenitic precipitation-hardening stainless steel that offers significantly higher tensile strength and fatigue resistance compared to 302 or 316 stainless steels. While 302 gains strength through cold working, 17-7PH undergoes a phase transformation and subsequent aging process that yields a typical tensile strength of $200$-$230$ ksi and an elastic modulus $E$ of approximately $28.5 \times 10^6$ psi. This allows for higher stress levels in smaller envelopes. Furthermore, 17-7PH exhibits superior dimensional stability during heat treatment and better relaxation resistance at operating temperatures up to $650^{\circ}F$ ($343^{\circ}C$), making it ideal for precision medical and aerospace actuators.
