Testing hydrogen embrittlement and stress corrosion using traditional methods would have required complex equipment, which the product development unit did not have in-house. “SSAB wanted a fast, cost-effective method for testing its own materials.” Her job was to get the tuning-fork test, developed in her master’s thesis at Aalto University, to work in SSAB’s product development laboratory. “It provides a fast, convenient way to test the hydrogen resistance of high-strength steels.”ĭevelopment first began in 2017 when Latypova got a summer job in the product development unit of steel company SSAB. In her highly practical doctoral thesis, Latypova developed a testing method, which is now more relevant than ever due to the hype around the hydrogen economy. The hydrogen released during the rusting process had induced hydrogen cracks, which in turn caused the whole tower to collapse. Investigation revealed that the reason for the collapse was rainwater in the prestressing steel tendons, which had caused them to rust. In Finland, hydrogen embrittlement made headlines in 2012 when the water tower of Kangasvuori in Jyväskylä collapsed. Johnson further inferred that the greater the strength of the steel, the more susceptible it is to hydrogen embrittlement. The first scientific article about hydrogen embrittlement was published in Nature in 1875. In the article, William Johnson studied hydrogen embrittlement by immersing samples of iron in different acids. The issue of hydrogen embrittlement has been well-recognized for a long time. “With hydrogen embrittlement, three factors are simultaneously at play, causing the final damage: a tensile stress state, a hydrogen-containing environment and a material that is susceptible to hydrogen”, says Latypova. The testing method applied in the doctoral thesis reveals how susceptible different steels are to hydrogen embrittlement. However, their crystal structure contains a surprising weakness: hydrogen atoms can easily enter the steel, inducing cracks. The strongest steels are the so-called martensitic steels that are formed by rapid cooling (quenching). The strength of steel largely depends on its microstructure. “Hydrogen embrittlement is an extremely severe issue that can lead to sudden, catastrophic failures in structural applications,” says Researcher Renata Latypova from the University of Oulu Centre for Advanced Steels Research in the lectio praecursoria that begins her doctoral thesis defence. These steels make structures lighter, but the downside is an issue known as hydrogen embrittlement. Researchers at the University of Oulu have focused on the development of ultrahigh-strength steels (UHSS).
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