On The Fatigue Crack Growth Behavior Of Ti-10v-2fe-3al In Gaseous Hydrogen

The fatigue crack growth behavior of Ti-10V-2Fe-3Al in gaseous hydrogen (H-2) was assessed through comparative experiments conducted in laboratory air and 8.3 MPa H-2. The measured fatigue crack growth rate (da/dN) versus applied stress intensity factor range (DK) relationships and observed fracture morphologies for laboratory air and H-2 were comparable up to Delta K approximate to 6.9 MPa root m, when tested at a load ratio of 0.1 and frequency of 10 Hz. At higher Delta K values, significant crack deflection and subsequent catastrophic failure occurred in the specimen tested in H-2. This degradation was not observed in a specimen pre-exposed to 8.3 MPa H-2 for 96 h and then immediately tested in laboratory air. X-ray diffraction of the failed H-2-tested specimen revealed that the material remnants were predominantly composed of TiH2, suggesting that hydride formation was the catalyst for catastrophic failure in H-2. The mechanistic implications of these results and their impact on current material compatibility assessments for Ti alloys in hydrogen service are then discussed. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.