Official Answer
Answer
17-7PH (Condition CH900) is suitable for temperatures up to $650^{\circ}F$ ($343^{\circ}C$). It provides high strength through a combination of cold reduction and precipitation hardening. However, beyond this temperature, the material undergoes over-aging and loses its spring temper. In contrast, Inconel X-750 is a nickel-chromium alloy that maintains its mechanical properties up to $1300^{\circ}F$ ($704^{\circ}C$) due to the $\gamma'$ (gamma prime) precipitate phase ($Ni_3(Al, Ti)$). For oil and gas downhole tools, X-750 is preferred not just for temperature, but for its resistance to chloride-induced stress corrosion cracking (SCC), whereas 17-7PH is susceptible to SCC in H2S-rich environments (sour service).
