Caracterização experimental da fragilização assistida pelo hidrogênio dos aços API 5L X60 e API 5L X80.

Abstract

The present work aims to study the hydrogen embrittlement process in steels API 5L X60 and API 5L X80. From electrochemical hydrogen permeation experiments were determined the following parameters - diffusivity, solubility and permeability in these steels. The studies were performed utilizing two types of embrittlement hydrogen conditions: environmental and internal hydrogen. The uniaxial tension mechanical behavior of steel type API 5L X60 and API 5L X80, with and without hydrogen, were studied. For the study of environmental hydrogen embrittlement, the steel API 5L X60 had a softening observed by the decrease in yield strength and increase its deformation. The API 5L X80 steel was more susceptible to the phenomenon due the deformation decrease of hydrogenated samples. For the study of internal hydrogen embrittlement, in both steels the change in deformation was significant and can be attributed to changes in hydrogen traps due to the hydrogenation process used, the chemical composition and microstructure. It can be concluded, as reported in the literature, that reversibly trapped hydrogen is more damaging than that which is held irreversibly. The fracture surface morphology of samples tested in tensile tests presented with characteristic ductile by coalescence of microvoids (dimples). It was observed that the distribution of dimples per unit area was higher in API 5L X60 steel samples hydrogenated.