HYDROGEN EMBRITTLEMENT OF MICROALLOYED STRUCTURAL-STEELS

The effect of Cr, Mo,V, Nb, Mn, their carbides and different microstru ctures on the corrosion and hydrogen uptake of two fine-grained microa lloyed steel grades has been investigated. In practice, fine-grained s tructural steels appear to be more or less susceptible to hydrogen ind uced cracking, probably because of various strong interactions between the absorbed hydrogen and the various alloying elements or their carb ides, acting as traps. The effect of microstructure was examined by ca thodic polarization, by measuring the reduction of area, and by SEM ex amination of the fracture surface. In addition, hydrogen permeation tr ansients for one microalloyed steel grade and Armco iron were measured , and the resistance of both steel grades to sulphide stress-cracking according to the NACE Standard TM-01-77 was also determined.