HYDROGEN TRAPPING IN HIGH-STRENGTH STEELS

Hydrogen trapping in three high-strength steels-AerMet 100 and AISI 43 40 and H11-was studied using a potentiostatic pulse technique. Irrever sible trapping constants (k) and hydrogen entry fluxes were determined for these alloys in 1 mol/l acetic acid/1 mol/l sodium acetate. The o rder of the k values for the three steels and two 18Ni maraging steels previously studied inversely parallels their threshold stress intensi ties for stress corrosion cracking (K-ISCC) Irreversible trapping in A erMet 100 varies with aging tem temperature and appears to depend on t he type of carbide (Fe3C or M2C) present. For 4340 steel, k can be cor related with K-ISCC over a range of yield strengths. The change in k i s consistent with a change in the principal type of irreversible trap from matrix boundaries to incoherent Fe3C. The principal irreversible traps in I-Ill at high yield strengths are thought to be similar to th ose in 4340 steel. (C) 1998 Acta Metallurgica Inc. Published by Elsevi er Science Ltd. All rights reserved.