Effect of Alloying and Heat Treatment on Embrittlement of Fe-Cr-Ni Alloys in High-Pressure Hydrogen.

The nickel content effects on the strength, plasticity, and low-cycle life of hardened and aged specimens of different modifications of austenitic iron-nickel steels and alloys in the initial state and after preliminary high-temperature hydrogenation in hydrogen at a pressure of 30 MPa and temperatures of 293, 773 and 973 K were studied. At 293 K, hydrogen embrittlement of hardened materials weakens with increasing nickel concentration from 10 to 23 wt.%; it is insignificant in the concentration range of 23–45 wt.% and significantly increases with higher nickel content. After aging, materials with a nickel content of 23 and 36 wt.% are insensitive to the action of the hydrogen environment; at higher hydrogen concentrations, embrittlement intensifies. The structural state of aged materials significantly affects the degree of hydrogen embrittlement of their various modifications during short-term tensile tests and slightly less during low-cycle fatigue tests. In the range of Ni concentrations of 23–73 wt.%, the effect of hydrogen on the relative transverse narrowing remains almost stable. The relative elongation of more hydrogen-resistant modifications of materials and low-cycle life increases with increasing nickel content. At 773 K, the effect of nickel content on the relative transverse narrowing in gaseous hydrogen at a pressure of 30 MPa is slightly smaller but qualitatively the same as at 293 K. At 973 K, more heat-resistant high-nickel alloys embrittle in a hydrogen environment much more strongly than hard dispersion steels. Thermomechanical treatment, according to the quenching scheme, tension at room temperature, and aging for 16 h at 973 K significantly increases the plasticity of materials in the presence of hydrogen at the same strength. [ABSTRACT FROM AUTHOR]