Abstract
It has been established that, at some region of hydrogen pressure and strain rate exists a maximum influence of hydrogen on the plasticity, low cycle fatigue and cyclic crack resistance of Ni-Co alloys and high nitrogen steels. The drop of plasticity of the dispersion-hardening materials within the temperature range of intense phase transformations is caused by the localization of strains on the grain boundaries due to the intense redistribution of alloying elements in the boundary regions. Moreover, the increase in plasticity observed at higher temperatures is caused both by partial coagulation of hardening phases and possible dissolution of small amounts of finely divided precipitations. The effect hydrogen on short-term strength and plasticity, high- and low-cycle durability of 15Cr12Ni2MoNMoWNb martensitic steel, 10Cr15Ni27Ti3W2BMo austenitic dispersion-hardened steel, heat resistant 3,5NiCrMoV rotor steel, 04Kh16Ni56Nb5Mo5TiAl and 05Kh19Ni55Nb2Mo9Al Ni-base superalloys in range of pressures 0–30 MPa and temperatures 293–1073 K was investigated. In the case of 15Cr12Ni2MoNMoWNb steel and 04Kh16Ni56Nb5Mo5TiAl alloy the dependence of low-cycle durability (N) and characteristics of plasticity (δ and φ) on the hydrogen pressure consists of two regions. In the first region (low pressures), the N, δ and φ abruptly drops, and in the second, the negative action of hydrogen becomes stable or decrease negligibility.
Highlights
The production of turbine and generator equipment requires a wide usage of dispersive hardened heatresistant Fe-Ni, Ni-Cr, Ni-Co alloys and high nitrogen steels
We reveal a significant decrease in the plasticity of heat-resistant nickel alloys in hydrogen under a MATEC Web of Conferences 165, 05002 (2018)
The specimens were held under the testing conditions for 30 min up to the attainment of thermal equilibrium. It has been established [1] that, at some values of hydrogen pressure and strain rate, which depend on the chemical compositions and structures of materials, maximum influence of hydrogen on the plasticity, low-cycle fatigue life, and static and cyclic crack resistance of martensitic steels and nickel alloys are achieved
Summary
The production of turbine and generator equipment requires a wide usage of dispersive hardened heatresistant Fe-Ni, Ni-Cr, Ni-Co alloys and high nitrogen steels. It has been established [1] that, at some values of hydrogen pressure and strain rate, which depend on the chemical compositions and structures of materials, maximum influence of hydrogen on the plasticity, low-cycle fatigue life, and static and cyclic crack resistance of martensitic steels and nickel alloys are achieved.
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