Hydrogen Embrittlement Of Ultrahigh Strength Cupronickel Alloy: Effects Of Exposure To Gaseous Hydrogen Environment On Fatigue Resistance

The ultrahigh strength cupronickel alloy Marinel and the nickel alloy Monel K-500 were saturated with gaseous hydrogen at 450°C and their fatigue behaviour was measured and compared with that of hydrogen free material. The presence of hydrogen was found to reduce thefatigue properties of Monel K-500, but did not affect the performance of Marinel alloy. No evidence of obvious microstructural change induced by hydrogen was apparent, but use of hydrogen diffusivity data was made in calculations relating to the diffusivity and trapping of hydrogen in the two materials. It was demonstrated that the solubility of hydrogen, the degree of dislocation-hydrogen interaction, and the ease of hydrogen trap formation (as a precursor to crack initiation) were lower in Marinel alloy than in Monel K-500, thus contributing to an explanation of the resistance of Marinel alloy to the debilitating effects of hydrogen.