Alert: Export Control Check Required
Thank you for requesting a TWI Industrial Members Report.
To meet UK government requirements, your request will undergo an Export Control Check. This process reviews the technical content of the report, identifies the end user, and addresses any concerns.
Please submit your request to CRP@twi.co.uk including your name, member company that you work for and your location. We will contact you regarding the request within 2 working days and any additional information required to complete the necessary checks.
We look forward to receiving your request and processing it through our export control procedure.
Thank you,
TWI CRP Operations Team
This content is only available to Industrial Members, Find out how to become a Member of TWI.
TWI Industrial Member Report Summary 1078/2016
By Michael Dodge
Background
Following a number of in-service failures, there is significant interest in understanding the microstructures and environmental conditions that contribute to hydrogen cracking of subsea dissimilar metal welds. Through a programme of environmental performance tests under cathodic protection, the environmental performance of F22 and 8630M-Alloy 625 interfaces has been evaluated.
High resolution electron microscopy (SEM and TEM) was used to determine the microstructures responsible for the observed environmental performance.
Key Findings
Following a programme of characterisation and environmental testing the key findings were as follows:
- The resistance to hydrogen cracking of dissimilar metals welds may be optimised by balancing competition between HAZ tempering and new phase formation.
- Optimal PWHT times were found to be below those which led to the precipitation of carbides within a narrow band adjacent to the fusion line.
- Cracks found in a retrieved dissimilar joint indicate subsurface initiation, secondary crack coalescence and progressive propagation.
Print version