Permeação de hidrogênio em superligas de níquel UNS N10276 e UNS N06022 pela técnica de Devanathan–Stachurski.

Abstract

This work presents a study on hydrogen diffusion in nickel-based superalloys, with emphasis on C22 and C276, which are widely applied in severe industrial environments, such as the petrochemical sector. The motivation for this research is related to hydrogen-induced embrittlement, a phenomenon that can compromise the structural integrity of pipelines and equipment, leading to critical failures in strategic systems. In this context, understanding hydrogen transport in highly corrosion-resistant materials represents an essential step toward the selection and development of suitable alloys.The main objective was to comparatively evaluate the diffusivity, permeability, and solubility of hydrogen in the two alloys under study, employing the electrochemical Devanathan–Stachurski technique, as specified by ASTM G148 (2018). For this purpose, C22 and C276 samples were sequentially ground and subjected to permeation tests in an electrochemical double-cell, using 3.5 % NaCl solution on the cathodic side and 0.1 M NaOH solution on the anodic side. This experimental procedure enabled the acquisition of current density versus time curves, from which transport parameters such as diffusion coefficient (D), permeability (φ), and solubility (S) were determined.The test results indicated that the C276 alloy exhibited slightly higher diffusion coefficients, demonstrating greater ease of hydrogen transport, while the C22 alloy showed higher solubility, indicating greater retention of the element in its metallic matrix. Despite these differences, the permeability values remained similar between the two alloys, as a result of the balance between the higher diffusivity observed in C276 and the greater absorption capacity verified in C22. Overall, the data indicate that although both alloys belong to the Ni-Cr-Mo family, C22 and C276 display distinct behaviors when interacting with hydrogen, but without differences of an order of magnitude. It is concluded that small variations in chemical composition influence the balance between diffusion and solubility, leading to comparable permeabilities.