Hydrogen in metals - from fundamentals to the design of new steels (HEmS)

Hydrogen is the lightest of the elements and has some remarkable properties and uses. Its isotopes will provide the nuclear fusion fuel for humanity in the next half century. Even now, it is probably the cleanest available fuel for motor cars and its extraction from sea water using solar power and subsequent transport around the globe is mooted as a potential solutions to our energy crisis. Because of its atomic size, hydrogen is not easy to contain as it diffuses readily through the lattice of solid materials, frequently by quantum mechanical tunnelling. The problem has a darker side; hydrogen has been known for over a hundred years to cause catastrophic failure in high strength steels. All welders know to keep their manual metal arc electrodes dry to avoid the generation of hydrogen from the decomposition of water during welding. The alloys resulting from our experiments and modelling will impact directly on the fuel efficiency of the next generation of automobiles, the service lifetimes of wind turbines and pipelines and lead to the development of new valve gear, and hydrogen handling and transport systems. We expect this to lead to improved profitability of our project partners and the sustainability of UK industry.

The project will develop new design procedures for ultra-high strength steels that resist embrittlement due to the presence of hydrogen for use in the above applications . This will be achieved through a series of advances in materials characterisation, testing and modelling. New experimental techniques will be developed to identify the structure of defects in engineering alloys and how they trap hydrogen. Understanding this trapping process is a key step in understanding how and why hydrogen embrittles steels. A range of modelling techniques from the atomistic through to the continuum will be developed and employed to provide detailed information about the embrittling mechanisms and how these depend on the steel microstructure. This will allow microstructures to be identified that are resistant to hydrogen embrittlement. This information will be employed to guide the development of new procedures for the design of alloys and heat treatments that result in steels that are resistant to attack by hydrogen. These techniques will be validated by processing a range of new alloys designed using our new methodology and examining their mechanical performance in the presence of hydrogen.

The alloys developed from our experimental and modelling activities will impact directly on the fuel efficiency of the next generation of automobiles and the service lifetimes of wind turbines and pipelines. They will also lead to the development of new valve gear, and hydrogen handling and transport systems. New procedures will be developed for the design of alloys and selection of heat treatments, which will directly benefit steel producers such as SKS and Tata steel, who will gain a competative advantage in each of the sectors identified above. This research will result in the development of more reliable steels for undersea pipelines operated by companies such as BP, providing a significant lifetime cost saving by increasing inspection intervals and extending the life of components. This research will also allow lightweight containment vessels to be developed for hydrogen storage for use in transport, resulting in a dual saving in cost through promoting the use of an energy efficient fuel and minimising vehicle weight. It will also allow improved mechancial gearing structures to be developed for largescale wind turbines, again reducing costs by increasing the life and durability of the structural components. We anticipate that impact will be realised within selected industries that are directly involved in this project within 2 years of completion of the grant. Global impact is likely to take an additional 5 years.

The techniques developed in this research will impact on other areas of technology. They can be extended to other systems that are prone to hydrogen embrittlement, such as zirconium fuel rod casing in nuclear reactors and titanium components in aerospace engines. Companies involved in the development and running of nuclear power plant, such as EDF Energy, and aerospace engines such as Rolls-Royce and British Airways, will directly benefit, with the new techniques allowing alloys to be developed that are more resistant to the agressive environments they operate in. Impact in these areas is likely to be within 20 years, but will require additional research to build on the work of the programme grant.

The full range of experimental and theoretical techniques developed in this research will be of benefit to a broad academic community. For example, the Baysian enhanced APT imaging techniques for the determination of defect structures and energies can be applied to a wide range of material defects and types of solute atmospheres. This will provide valuable new insights into defect structures and how they influence material behaviour. Similarly, the project will result in significant advances in a range of modelling techniques, from atomistic through to continuum, and their integration to provide material models across a wide range of temporal and spacial scales. These techniques will be relevant to any modelling activity that focuses on inelastic deformation, material degradation and fracture, or the development of microstructures during processing or high temperature exposure. The impact of these techniques is likely to be signifiant within the lifetime of the grant.