1.6759 | G18NiMoCr3-6 fisheye, hydrogen embrittlement

A fisheye caused by hydrogen appears macroscopically as a circular smooth fracture surface. In the center there is always a flaw such as a slag inclusion or, as in the present case, a microlunker where the hydrogen could accumulate. The topographic fracture appearance of the fisheye is a finely feathered, transcrystalline brittle fracture surface. The formation of the fisheye begins as soon as the material is stressed beyond the yield point. Outside the fisheye, a dimple fracture structure is present.