Estudo da inflluência da pré-deformação na fragilização por hidrogênico do aço UNS S32750

Abstract

Hydrogen embrittlement is a recurring phenomenon, especially in high-strength metallic components operating in hydrogen-rich environments. Hydrogen absorption promotes the reduction of ductility in metallic components, making them brittle and susceptible to catastrophic failures. Among the materials commonly used in aggressive environments containing abundant hydrogen, duplex stainless steels (DSS) and super duplex stainless steels (SDSS) stand out, particularly in the chemical and petroleum industries. This study investigates how pre-strain can influence hydrogen embrittlement in super duplex stainless steel UNS S32750. For this purpose, specimens with diferent pre-strain levels were hydrogen charged and tested in uniaxial tensile at the National Synchrotron Light Laboratory (LNLS) in Campinas - SP. The experimental station where the tests were carried out allowed the capture of X-ray diffraction profiles from the specimens while they were mechanically tested. In addition to the mechanical results, with proper treatment, the diffraction profiles enabled the evaluation of microstructural parameters, such as the average crystallite size and the dislocation density. Fractographic analysis and Electron Backscatter Diffraction (EBSD) were also performed on the tested specimens to investigate the fractured surface and the texture components present in the regions near the fracture. The

mechanical results revealed an intensification of hydrogen embrittlement in the pre- strained specimens. The embrittlement indices ranged from 29.6% to 38.1% for the

non-pre-strained condition (0%), while for the pre-strained specimens, they ranged from 52% to 60.6%. The total elongation decreased with increasing pre-deformation, especially for 11%, 22%, and 33%, and was further reduced for the hydrogen charged material, highlighting the embrittlement and confirming the influence of pre-strain on the phenomenon.