ULTIMET® alloy

Sulfide Stress Cracking

• Wrought ULTIMET alloy has been tested according to NACE TM0177, which defines sulfide stress cracking as a room temperature phenomenon, resulting from hydrogen embrittlement.
• The TM0177 tests involved 5% NaCl + 0.5% glacial acetic acid, saturated with H₂S, proof-ring apparatus, and samples coupled to carbon steel and stressed to the point of yield.
• ULTIMET alloy was able to withstand these conditions, both annealed and cold-reduced (15%), indicating good resistance to hydrogen embrittlement. 

H₂S – Induced Stress Corrosion Cracking

• Cracking at elevated temperatures in environments containing H₂S is defined as a form of stress corrosion cracking.
• Wrought ULTIMET alloy has been tested in 20% NaCl + 0.517 MPa (75 psi) H₂S + 4.83 MPa (700 psi) CO₂, with and without 0.5 g/l sulfur, at 121°C and 177°C; the tests were conducted according to the recommendations of ASTM Standard G 39, the fixtures being made of ULTIMET alloy, to prevent galvanic effects.
• Like other materials, ULTIMET alloy was prone to cracking in the cold-reduced condition, but resistant to H₂S-induced stress corrosion cracking in the annealed condition, at these temperatures.