Through the microscope: SEM image of a hydrogen-induced fracture surface

“Absolutely beautiful” was how our testing laboratory colleagues at the MaterialtestCenter and ExpertCenter described this scanning electron microscope (SEM) image. The high-resolution detail at 5,000× magnification shows the fracture surface of a high-strength chain link, revealing an almost ideal example of the microscopic features of hydrogen-induced embrittlement.

Classic features of hydrogen embrittlement

The image reveals several typical features regarded in damage analysis as characteristic of hydrogen-related damage:

• opened-up grain boundaries
• local microplastic deformation (“crow’s feet”)
• a single pore on the intergranular facets

This combination makes the image a particularly clear example of the microscopic characterisation of hydrogen-induced fracture mechanisms.

Technical context: Hydrogen embrittlement

The commonly used term hydrogen embrittlement describes changes in a material’s mechanical properties caused by hydrogen entering and becoming incorporated into the metal lattice. This can significantly increase the material’s brittleness.

The more precise technical term for the damage mechanism shown here is cathodic stress corrosion cracking. The resulting damage can lead to hydrogen-induced cracking and subsequently to brittle component fractures. Such mechanisms are particularly relevant to high-strength steels and also present challenges in hydrogen storage and technology applications.

Teaching material for damage analysis

Because its structures are exceptionally clear, this image is likely to appear soon in the W.S. TrainingCenter’s training materials – for example in the GSA course “Fundamentals of damage analysis” and the W.S. Spezial seminar “Technical damage analysis” (SemTSA).

Real SEM images like these provide considerable educational value, particularly in training on materials engineering damage analysis, because typical damage mechanisms can be understood directly.