OBSERVATION OF TRAPPING SITES OF HYDROGEN AND DEUTERIUM IN HIGH-STRENGTH STEELS BY USING SECONDARY-ION MASS-SPECTROMETRY

Hydrogen and deuterium trapping sites in high-strength steels have bee n observed by secondary ion mass spectrometry(SIMS). High-strength ste els with 1400 MPa tensile strength are stressed and dipped in D2O and 20% NH4SCN solution at 323 K to occlude hydrogen and deuterium. Depth profiles by SIMS show the presence of deuterium, which indicates hydro gen trapping sites occluded during the delayed fracture test. Secondar y ion image analysis by SIMS has made it possible to observe hydrogen and deuterium trapping sites in high-strength steels. Hydrogen tends t o accumulate at grain boundaries, in segregation bands, and on inclusi ons. Line scans by SIMS have shown that the accumulation ratios of hyd rogen for the grain boundaries, segregation bands of P and inclusions are 7.8, 5.0 and 11.0 times higher than that in the matrix, respective ly. Hydrogen trapping sites at the grain boundaries can be observed by measuring within 24 h after the delayed fracture test.