Authors

F. Heine, C. Schnatterer, U. Merschrod, T. Jene, H. Dieterle, KAMAX Automotive GmbH, Homberg (Ohm)

Year

2026

Print Info

Production/Publication ÖVK

Summary

Hydrogen embrittlement is one of the key challenges for high-strength and ultra-high-strength bolts and continues to limit their application in the automotive industry. This is particularly relevant for chassis components, electric powertrains, and battery fixations which—due to their exposure to the environment—face an increased risk of corrosion and hydrogen uptake. As a result, the use of ultra-high-strength bolts in such applications remains restricted.

The author´s innovative approach enables a further, previously unattained increase in resistance to hydrogen embrittlement. Prior to quenching and tempering, a thin nickel coating is applied to the fasteners. During the subsequent heat treatment, this layer thermally diffuses into the steel substrate, leading to stabilization of austenite in the near-surface region. This austenite-stabilized layer does not transform into martensite or bainite during quenching but instead retains its austenitic crystal structure, thereby acting as an effective diffusion barrier against hydrogen. This ensures, that the fasteners are reliably protected even under service conditions with a high risk of hydrogen uptake.

Investigations have demonstrated that bolts treated with this process exhibit significantly improved resistance to hydrogen-induced brittle fracture, even in the highest strength levels. This substantially surpasses the current state of the art.

ISBN

978-3-9504969-5-6

DOI

https://doi.org/10.62626/hyn1-a7au Copy link

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