Session: 03-04-01 Environmental Effect on Materials Performance

Paper Number: 79852

79852 - Effect of Temperature on Resistance to Hydrogen Embrittlement of Dissimilar Metal Welds Subjected to SENB and SENT Testing 

Dissimilar metal welds (DMWs), as manifested by low alloy steels welded with nickel alloys, are commonly used in subsea production systems. In such applications, there is a risk of hydrogen embrittlement, due to the use of cathodic protection. Historically, one of the most reliable means of establishing the resistance of DMWs to hydrogen embrittlement has been to conduct fracture mechanics-based tests, under representative service conditions. These tests have proved valuable in ranking the performance of various DMWs and, also, emulating the fracture morphologies observed in many subsea failures. 
Much of the established data from these tests has been generated using single edge notched bend (SENB) specimens, tested at the seabed temperature, to produce ‘tearing resistance’ J R-curves. However, whilst it is recognised that most failures have occurred after equipment has been shutdown, there has been little exploration of how parameters, such as temperature and loading mode, influence the resistance to hydrogen-assisted cracking. This paper uses the results of SENB and single edge notched tension (SENT) tests on DMWs, consisting of 2.25Cr-1Mo Grade F22 welded with ERNiCrMo-3 (Alloy 625), to understand how temperature and level of constraint affect fracture resistance, at a range of temperatures (4 to 80˚C). The merits and drawbacks of both techniques are summarised, alongside the practical implications for subsea components currently in operation.

Presenting Author: Michael Dodge TWI Ltd.

Authors:

Michael Dodge TWI Ltd.
Lars Magne Haldorsen Equinor ASA
Mike Gittos TWI Ltd
Kasra Sotoudeh TWI Ltd