Comparing Hydrogen Transport and Trapping Mechanisms: Controlling Embrittlement as a Function of Charging Method in Steels and Nickel Alloys

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Many current and next generation energy systems are reliant on the production, transportation, storage and use of gaseous hydrogen, often at high pressure. The safety, durability, performance, and economic operation of such systems are challenged due to the reality that hydrogen promotes a variety of degradation modes in otherwise high performance materials. Such degradation is often manifested as cracking which compromises the structural integrity of metals and polymers; a behaviour complicated by time and operating cycle (e.g., stress, hydrogen pressure, and temperature) dependencies of degradation. As an example, concurrent stressing and hydrogen exposure at typical pressure vessel or pipeline environmental conditions can promote cracking in modern metallic systems at one-tenth the fracture toughness. Such hydrogen-induced degradation phenomena are generally categorised as hydrogen embrittlement. The breadth and importance of hydrogen damage phenomena have not gone unnoticed in the scientific community with an immense amount of work conducted over the past 100 years. The problem is broadly interdisciplinary and such work has involved metallurgy, chemistry, solid mechanics and fracture mechanics, surface science, molecular and atomic hydrogen physics, non-destructive inspection, materials characterisation, and mechanical-properties testing. This important work notwithstanding, major challenges face those tasked with managing complex engineering structures exposed to demanding environment and mechanical loading conditions. The challenge here is to transform debate on mechanisms of hydrogen damage into a focus on quantitative, predictive models of material cracking properties. Overarching these challenges is the inescapable fact that hydrogen damage problems are immensely complex, requiring understanding of time-cycle dependent processes operating at the atomic scale to impact behaviour manifest at the macroscopic scale.In this study we will attempt to characterise the hydrogen solubility, transport and trapping which govern embrittlement associated with cracking of a range of Steel and Nickel-based alloys as a function of hydrogen charging technique (i.e., gaseous charging vs electrochemical charging). Initial experiments will include hydrogen permeation studies and thermal desorption analysis for hydrogen diffusion and trap character of the above-mentioned alloy systems. Further experimental work could include fracture mechanics / fracture toughness testing as well as analytical electron microscopy. This research project is funded in part by Element Materials Technology who will also provide co-supervision. Element Materials Technology is a global provider of testing, inspection and certification services to industry, with over 200 laboratories conducting destructive testing and non-destructive testing of metals, composites, polymers, elastomers, and resins to determine their potential properties, performance, strength, durability, and resistance to corrosion. The candidate will also make use of the state-of-the-art testing facilities located within the Henry Royce Institute for Advanced Materials Research and Innovation at the University of Manchester.