|About this Abstract
||2014 TMS Annual Meeting & Exhibition
||Multiscale Approaches to Hydrogen-assisted Degradation of Metals
||Hydrogen Environment Assisted Cracking (HEAC) of Modern Ultra-high Strength Stainless Steel
||Greger Pioszak, Richard Gangloff
|On-Site Speaker (Planned)
Two Ni3Ti-strengthened martensitic stainless steels, aged to high yield strength (1700-1860 MPa), exhibit markedly different HEAC in 3.5% NaCl solution. Both alloys resist cracking within a polarization window mildly cathodic to open circuit (-225 mVSCE) where threshold stress intensities approach KIC (75-100 MPa√m). Severe intergranular cracking occurs in Custom®465-H900 when cathodically polarized below -475 mVSCE, with thresholds of 10-14 MPa√m and Stage II crack growth rates of 1-3 μm/s. Ferrium®PH48S™-H900 is susceptible to HEAC, but only below -600 to -750 mVSCE; thresholds are similar at -975 mVSCE, but Stage II growth rates are consistently lower (0.1-0.2 μm/s) and cracking is transgranular likely through martensite interfaces. Reduced growth rates may be attributed to H trapping at dispersed TiC, which reduces H diffusivity in Ferrium®PH48S™. The transition from intergranular to transgranular HEAC may relate to a grain boundary phase, elemental segregation, or H localization. Experiments are in progress to test these hypotheses.
||Planned: Paper Selections