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Resistance to Stress Corrosion Cracking

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. 
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