Official Answer
Answer
Elgiloy (complying with NACE MR0175) is the gold standard for sour gas environments due to its extreme resistance to Stress Corrosion Cracking (SCC) and Hydrogen Embrittlement. Unlike carbon steels or even some stainless steels, Elgiloy's cobalt-base chemistry prevents the formation of brittle hydrides. Its fatigue resistance is also superior in corrosive media. When processing Elgiloy wave springs, the material is typically cold-worked and then age-hardened at $900^{\circ}F$ to $1000^{\circ}F$. This results in a material with high elastic modulus ($E \approx 28.5 \times 10^6$ psi) and high corrosion fatigue limits, essential for the 20-year service life required in subsea BOP (Blowout Preventer) stacks.
