Caracterização 3D de trincamento assistido pelo meio na presença de sulfetos em aço inoxidável supermartensítico utilizando tomografias de raios x e nêutrons

Abstract

For the present work, the susceptibility to environmentally assisted cracking in the presence of H2S was investigated, as well as the evolution of pits and cracks, in a supermartensitic alloy 13Cr-5Ni-4Mo-0.02C (mass percentage). The EAC tests were performed in modified Solution C of the NACE TM0177-2016 standard - Method A [3], in the presence of mechanical stress of uniaxial stress where the predominant mechanism of corrosion observed is pitting corrosion, stress corrosion and embrittlement by hydrogen. Visual analyzes and depth measurements of pitting / cracking were performed using optical microscopy and additionally, analyzes and measurements of these pits and cracks were performed using X-ray tomography as well as the verification of the presence of hydrogen using the neutron technique. Making it possible, to determine the mean depth of the pit which occurs the transition between pit and crack and by means of neutron tomography, the presence of metal hydroxides was found inside the cracks. Based on the measurements made and the time of exposure of the samples, the crack growth rates (da / dt) in each stage were calculated.