Analysis of hydrogen trapping by gaussian distribution for normalized carbon steels

Abstract

For the basis of understanding hydrogen embrittlement, hydrogen thermal desorption curves are subjected to the analysis for making clear the kinds and amounts of traps in normalized carbon steels that are composed of ferrite and pearlite. While the theoretical desorption curves should be analyzed basically by non-symmetrical curves such as obtained by Kissinger equation, the measured curves are also deformed and approach to symmetrical form. Actually they are successfully fitted by combination of two symmetrical Gaussians; one is desorption from dislocation trap and the other is from grain boundary trap. Applying this method to different heats of JIS S45C steel, grain boundary trap of high phosphorus content shifts to higher temperature side, suggesting that hydrogen trap is enhanced by phosphorus segregation along grain boundary. An increase in cathodic current density causes more hydrogen partition to grain boundary. Analysis with the use of Gaussian is practical and reasonable to understand the properties of hydrogen traps. © 2014 ISIJ.