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Sour service performance of 625 overlay/clad versus solid 625 material

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  • Full or part time
    Dr K Sotoudeh
  • Application Deadline
    Applications accepted all year round

About This PhD Project

Project Description

Petroleum fields can either be ‘sweet’ (i.e. just CO₂-containing) or ‘sour’ (i.e. both CO₂ and H₂S-containing). The major threat associated with sweet services is mainly corrosion wastage (general or localised) and thinning of the wall thickness through time that can be predicted and inspected for, whilst the major threat associated with sour service is sudden and unpredictable cracking, with detection in a timely manner by inspection difficult, if not impossible. The resistance to sour service is material specific and the acceptable limits are codified in the international standards (ISO 15156 and NACE MR0175). These standards do not fully address welded / cladded / lined corrosion resistant materials, leaving the decision on suitability responsibility with the operators.

End Goal - to establish the relationship between weld overlay type/chemistry and resistance to sour service cracking, taking into account the manufacturing variability in terms of weld chemistry/welding process / procedure / consumables, and post welding / cladding heat treatment, and to define rules for safe operating limits.

Industrial Need – Corrosion resistant alloy weld overlay / clad / liner options offer ab economical solution to corrosion for pipelines, flowlines and equipment in severe operating environments. Welded alloys are, by their nature, different from solid wrought materials such as tubulars, forgings, etc. (welds have a cast microstructure). In addition, as part of the manufacturing process, these barriers can be subjected to heat treatment. This could result in chromium carbide precipitation (amongst other precipitates), which could impair the corrosion resistance properties. There is currently no guidance on how to deal with this in the international standards IOS 15156/NACE MR0175.

Project Overview – The project will need to develop an understanding of the influence of the weld chemistry and heat treatment on the microstructure of 625overlay / clad / liner, especially with respect to iron dilution/content (weld chemistry) and carbide precipitation (heat treatment) and to understand the impact of these variations on the corrosion resistance performance. Corrosion performance will be assessed using standard test methods, such as ASTM G28, as well as in simulated service conditions.

A number of fully-funded PhD scholarships are available for suitable candidates with a strong interest in fundamental and applied research in the area of structural integrity. Scholarships cover an amount to £16,000 per annum for 3 years, Home/EU tuition fees and support for research. Overseas applicants are welcomed, with total funding capped at £20k/year.

Candidates should have a relevant degree at 2.1 minimum, or an equivalent overseas degree in mechanical, Electrical/Electronics or Civil/Structural Engineering, Material Science, Metallurgy or Physics. Candidates with suitable work experience and strong capacity in numerical modelling and experimental skills are particularly welcome to apply. Overseas applicants should also submit IELTS results (minimum 6.5) if applicable.

To apply, please send your CV and transcript of university study, with a cover letter specifying your interest and research topic to the following email address: [email protected]
Please direct general enquiries to: [email protected]

NSIRC will be a state-of-the-art postgraduate engineering facility established and managed by structural integrity specialist TWI, working closely with lead academic partner Brunel University, the universities of Cambridge, Manchester, Loughborough, Birmingham, Leicester and a number of leading industrial partners. NSIRC aims to deliver cutting edge research and highly qualified personnel to its key industrial partners.

For more information about The National Structural Integrity Research Centre, visit

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