33 Fatigue Crack Growth of A C-Mn Steel and Associated Weld Under Hydrogen Pressure
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Published:2014
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The Fatigue Crack Growth (FCG) in high-pressure hydrogen gas of a ferritic-pearlitic X80 steel is studied. Both the Base Metal (BM) and the associated weld (Heat Affected Zone HAZ and Melted Zone MZ) are analyzed considering the influence of the hydrogen pressure and testing frequency. FCG rate in 10 MPa hydrogen gas is higher than in air, while slopes of da/dn(ΔK) curves in both environments are roughly similar. FCG rates in hydrogen of HAZ and MZ microstructures are the same, whereas the one of BM is slightly lower. In the investigated range, no testing frequency effect in hydrogen is observed. A slight decrease of FCG rate is noticed in 3 MPa of hydrogen gas compared to 10 MPa. Finally, regarding both previous studies [1–5] and our results, it appears that FCG in hydrogen is governed by a competition between crack propagation rate and hydrogen diffusion to reach a critical hydrogen content ahead of the crack tip for the embrittlement process to occur.