The Influence of Microstructure on Hydrogen Diffusion and Embrittlement of Multiphase Fine-Grained Steels with Increased Plasticity and Strength

A. Begić Hadžipašić, J. Malina and M. Malina

Abstract
The influence of microstructure on hydrogen diffusion and embrittlement of multiphase fine-grained structural steels with increased plasticity and strength was studied with electrochemical experiments which provide the hydrogenation of specimens in conditions simulating practice requirements. By means of all experimental data obtained from permeation experiments, mechanical investigations, SEM and EDS analyses, TRIP steel has shown greater resistance to hydrogen embrittlement than DP steel, testified by lower index of hydrogen embrittlement, lower diffusion coefficient, less inclusions and favourable microstructure with residual austenite. Namely, the residual austenite in the aspect of hydrogen embrittlement is a favourable phase in relation to martensite, because of its higher solubility of carbon and hydrogen and lower hardness. Therefore, TRIP steel could be considered the more suitable structural material than DP steel for application in conditions where contact with hydrogen is inevitable.

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Keywords
Fine-grained HSLA steels, hydrogen diffusion, electrochemical methods, microstructure, mechanical properties, hydrogen embrittlement