Data‐analysis method for hydrogen embrittlement tuning‐fork test

Pohjonen, Aarne; Latypova, Renata; Seppälä, Oskari

doi:10.1002/maco.202313925

Cited by 1 publication

(1 citation statement)

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“…These time values can be determined with a data analysis method that utilises second-order time derivatives of fitting functions as presented in Ref. [9]. TFT tests with ISLT produce promising results but further research and more repetitions are necessary for data quantification.…”

Section: Materials Application In Industriesmentioning

confidence: 99%

Hydrogen Embrittlement in as-Quenched Martensitic Steels - Application of Incremental Step Loading Technique with Novel Tuning-Fork Test

Latypova,

Nyo,

Kömi

et al. 2023

KEM

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Hydrogen embrittlement (HE) is a well-known issue, especially with ultrahigh-strength steels (UHSS). Various testing methods are utilised to study HE, but they typically require tensile test equipment, or are impractical due to limited stress control with standard geometries. We have developed a novel Tuning-fork test (TFT) to study HE susceptibility of steels with a new specimen geometry, which can be stressed accurately without tensile test equipment. The test method utilises in situ electrochemical hydrogen charging and constant displacement for stressing of the notched specimens by bending. Crack initiation and propagation are controlled with an isolated tensile stress region, and the failure process is monitored with a loadcell. TFT is a simple and fast testing method, which allows ranking of UHSSs, and to investigate, e.g., microstructural effects on susceptibility to HE and H-induced fracture processes. Here in this study, we present the state-of-the-art with the improved more precise second-generation TFT setup, which benefits from a more sensitive loadcell and a more stable fine-tuneable differential screw adjustment. We extend TFT to testing of martensitic steels with nominal hardness from 400 HBW to 600 HBW with the Incremental step loading technique (ISLT). The results show that TFT with ISLT is well applicable for ranking ultrahigh-strength steels based on their susceptibility to HE. Force-time data from ISLT can also be used for the determination of a material-specific threshold stress level, and the last step for the calculation of a crack initiation-time and time-to-fracture. However, the current manual operation of the loading screw can still limit maximum duration of a test.

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Section: Materials Application In Industriesmentioning

confidence: 99%