About the Project
High temperature hydrogen attack (HTHA) is a material degradation and cracking mechanism caused by reduction of carbides within steel, resulting in the substitution of carbides by bubbles of methane gas. The strengthening effect of carbides is lost, and the material is further weakened by the presence of gas filled voids, which may link up to form fissures or cracks.
HTHA is seen in steels which are operating in hydrogen rich atmospheres at temperatures which are high enough for molecular hydrogen to dissociate and dissolve into the steel, and to react with the carbides. The risk of HTHA is managed in industry by guidelines presented in API RP 941. In this document, plots of temperature vs. partial pressure of hydrogen are presented, which are populated with data on occurrence of HTHA and also successful operation without HTHA, which have been collected principally from refinery operation since the 1940s. The plots were originally produced by G. A. Nelson and the boundaries between regions with and without HTHA are known as “Nelson Curves”.
Recent incidents of HTHA under conditions which were expected to be safe according to the Nelson curves have been attributed to the effects of residual stress. There are other possible contributory factors, however, which have received insufficient attention. In particular, the composition, stability and distribution of carbides in weld heat affected zones (HAZs), and the possible contribution of dissociation of gasses other than H2 (such as H2S) to hydrogen within the steel.
In an initial project, the effects of H2S on HTHA will be explored by comparing the effects of different gas mixtures on steel samples in a simple furnace. In future work the effects of simulated and/or real HAZs could be explored. The use of simulated HAZs would allow the possible effect of residual stress to be eliminated, so that microstructural effects could be investigated. The effect of stress can be explored, but would require development of equipment capable of applying a load to a specimen within a high temperature, pressurised hydrogen atmosphere.
Academic requirements
Study of this subject area will require an understanding of relatively high temperature surface chemical reactions on steel, and in particular the interaction of gases with a steel surface in a typical (oxidised) commercial condition. The University department should also be able to contribute expertise in the diffusion and chemical reactions taking place within steel. An understanding of ferritic steel metallurgy would be advantageous.
Candidates should have a relevant degree at 2.1 minimum, or an equivalent overseas degree in Computer Science, Electrical Engineering or another scientific field that includes digital signal processing. Candidates with suitable work experience and strong capacity in machine learning, programming or signal processing are particularly welcome to apply. Overseas applicants should also submit IELTS results (minimum 6.5) if applicable.
About NSIRC
NSIRC is 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.
http://www.nsirc.com/
About the University
The University of Leicester is a public research university based in Leicester, England. The main campus is south of the city centre, adjacent to Victoria Park. The university established itself as a research-led university. It was previously ranking among the top 20 universities in the United Kingdom and was ranked 13th in 2014 by the Guardian. In 2008, it was awarded University of the Year by the Times. As of 2016/17 the university is nationally ranked 25th in The Sunday Times Good University Guide, and 29th in the latest The Complete University Guide. It is ranked as one of the top 200 universities in the world by the Times in 2017.
Funding Notes
Up to £24k in scholarships
This project is funded by Lloyds Register Foundation, TWI and academic partners. The studentship will provide successful Home/EU students with a stipend of £16k/year and will cover the cost of tuition fees. Overseas applicants are welcome to apply, with total funding capped at £24k/year