engleski

SEM Appearance of Hydrogen Cracks in Weld beads on Steel

The aim of the present work was to investigate the influence of hydrogen on the tensile strength and ductility of welded high-strength structural steel by applying electrochemical charging. Hydrogen embrittlement and rupture of weld beads was studied on specimens of low-alloy low sulphur steel. The micrographic observation of cracked specimens show that the main difference caused by H-charging is connected with the morphology of the fractured surface. Without charging, fracture is ductile with dimple rupture type characteristics for tough metal materials, where fracture is running according to the mechanism of coalescence of microvoids. However, the equiaxial cracks prevail in H-charged specimens, and so-called fish eyes are visible. The fractographic appearance changes from ductile to cleavage and quasicleavage morphology, where the decohesion between the base metal and the weld is well visible. This can be explained by a higher hardness of the metal in this zone, caused by the microstructure resulted from the specific features of the temperature field formed during the welding process.

SEM; hydrogen cracks; weld beads

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