Answer
Inconel X-750 (UNS N07750) is the industry standard for subsea oil and gas applications due to its exceptional resistance to chloride-ion stress corrosion cracking (SCC) and hydrogen embrittlement. The material is typically heat-treated to the NACE MR0175 standard to ensure performance in sour gas ($H_2S$) environments. The hardening process involves solution annealing followed by precipitation aging, which creates $\gamma'$ ($Ni_3(Al, Ti)$) precipitates. These precipitates pin dislocations, providing a high yield strength at temperatures ranging from cryogenic to $1300^{∘}F$ ($704^{∘}C$). When designing wave springs for deep-water valves, the lower shear modulus $G$ and Young's Modulus $E \approx 31 \times 10^6$ psi must be used in the rate calculations to ensure the spring provides sufficient sealing force at $10,000$ psi ambient pressure.
