Answer
Inconel X-750 (UNS N07750) is a nickel-chromium alloy made precipitation-hardenable by additions of Al and Ti. It is highly resistant to chloride-ion stress corrosion cracking and sulfide stress cracking (NACE MR0175 compliance), making it ideal for sour gas environments. A286 (UNS S66286) is an iron-base superalloy that is more cost-effective and provides excellent oxidation resistance up to $1300^{\circ}F$. However, for subsea applications involving high-pressure, high-temperature (HPHT) and seawater exposure, Inconel X-750 is preferred due to its superior resistance to hydrogen embrittlement and better relaxation resistance. While A286 has good tensile properties, its localized pitting resistance in stagnant seawater is lower than that of X-750.
