Mechanisms of Crack Tip Hydrogen Embrittlement in High Strength Alloy Steels for Marine Applications
Abstract
The primary objective of this research was to characterize and understand (a) the interaction of a range of bulk-dissolved hydrogen concentrations with the complex tempered martensitic microstructure of AerMet 100 ultra-high strength steel, (b) the effect of such trapped hydrogen on fracture resistance associated with internal hydrogen embrittlement (IHE), and (c) the levels of trapped and diffusible hydrogen achieved after cadmium plating and baking operations. Studies of hydrogen transport rates, trapping and redistribution after heating sought to correlate embrittlement-threshold levels with redistribution of diffusible hydrogen during IHE. A strong dependence of the threshold stress intensity (K(th) for the onset of IHE in AerMet 100 on diffusible H concentration was measured and modeled in this project. H was trapped at the interfaces of M(2)C precipitates that are responsible for strengthening of peak aged AerMet 100. Modeling showed that very high levels of H can redistribute within the crack tip process zone and promote transgranular fracture due to two factors; unexpectedly high crack tip normal and hydrostatic stresses, as well as substantial weak reversible H trapping at M(2)C precipitates unique to AerMet 100. Upon stressing, H redistributes to the crack tip process zone due to lattice dilation from the crack tip stress field.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 2002
- Accession Number
- ADA408121
Entities
People
- Dapeng Li
- E. Richey Iii
- John R. Scully
- R. L. Thomas
- R. P. Gangloff
Organizations
- University of Virginia