RELATIONSHIP BETWEEN MICROSTRUCTURE AND HYDROGEN PERMEATION OF A PLASTIC DEFORMED SEAMLESS CARBON STEEL PIPE

摘要

The main objective of this work was to study the effect of plastic deformation (cold work) and heat treatment on the hydrogen permeation of a seamless carbon steel pipe, commonly used in the oil industry, considering the relationship between microstructure and hydrogen diffusion. The steel samples were characterized, by scanning and transmission electron microscopies to establish the relationship between microstructure and defects on the hydrogen damage.The hydrogen permeation tests were performed on samples of the above mentioned steel in the different conditions. The experiments were carried out following the Devanathan and Stachurski technique, using 0.1 M Na_2SO_4 as the electrolyte in the cathodic compartment and 0.1 M NaOH as the electrolyte in the anodic one. The obtained results showed that the hydrogen absorption capacity is higher when the steel has the larger deformation degree. This could be associated to the presence of substructures with small cell size range (0.01-0.15 μm), meaning a higher dislocation density, which could act as a preferential site for a greater hydrogen absorption and transportation. On the other hand, with increasing deformation, the mean hydrogen flux is greater than measured through steel in the as received condition.