Next Generation Electro-Chemo-Mechanical Models for Hydrogen Embrittlement (NEXTGEM)

Hydrogen is ubiquitous and has two faces. On the one hand, it is at the core of the most promising solutions to our energy crisis. Hydrogen isotopes fuel the nuclear fusion reaction, the most efficient potentially useable energy process. Moreover, hydrogen is widely seen as energy carrier of the future and the most versatile means of energy storage. It can be produced via electrolysis from renewable sources, such as wind or solar power, and stored to be used as a fuel or as a raw material in the chemical industry.

On the other hand, hydrogen is widely known to cause catastrophic failures in metallic materials and structures, hampering these opportunities. Metals become brittle when exposed to hydrogen-containing environments, with the fracture resistance decreasing by up to 90%. This so-called hydrogen embrittlement phenomenon not only jeopardises the role of hydrogen as a potential solution to the global energy crisis but also constitutes one of the biggest threats to the integrity of the current energy infrastructure. The problem is particularly severe in aggressive environments, such as those experienced by the offshore industry, as corrosive mitigation strategies like cathodic protection exacerbate the production of hydrogen. Moreover, hydrogen embrittlement is becoming increasingly notorious due to the higher susceptibility of modern, high-strength steels. Decades of metallurgical research have led to the development of metals with high and ultra-high strengths. These modern alloys open new horizons in reducing weight, material use and costs while increasing performance and safety (fatigue resistance). For example, ultra-high strength steels are essential in meeting targets on CO2 emissions through vehicle weight reduction. However, the susceptibility to hydrogen embrittlement increases with material strength and the increasing uptake of these new high-performance materials has made hydrogen assisted fractures commonplace across a wide variety of sectors and applications in otherwise benign environments, from bolt cracking at the Leadenhall tower to rail failures in underground systems. There is an urgent need to understand the multiple physical mechanisms behind this hydrogen-induced degradation and develop models that can predict failures as a function of the environment, the loading conditions and the material properties.

This EPSRC New Investigator Award aims at developing a new generation of models that can predict local hydrogen uptake and subsequent cracking by resolving the electrochemistry-diffusion interface and shedding light into critical uncertainties in surface behaviour and trapping. An accurate estimation of hydrogen ingress for a given bulk environment is the main bottleneck preventing the application of current chemo-mechanics models in engineering assessment. Occluded areas such as cracks, pits or other defects exhibit very different chemistry to the bulk environment, and local measurements are unfeasible apart from controlled laboratory experiments. NEXTGEM will merge mechanics with electrochemistry, combining experiments, multi-physics modelling and Bayesian inference to resolve the scientific challenges holding back the applicability of hydrogen embrittlement models. This new generation of electro-chemo-mechanics models for hydrogen embrittlement will be used to enable a safe use of high strength alloys, optimise material selection and inspection planning, and prevent catastrophic failures.

The project involves world-renowned academic collaborators with expertise complementary to that of the PI and leading firms in the offshore energy sector, operating the oldest large-scale wind farm in the world (Horns Rev 1). The applicability of the models developed will be demonstrated by continuous monitoring of critical components, in a piece of proof-of-concept research that can have wider implications across the transport, defence, construction and energy sectors.