Effect of environmental and internal hydrogen on the hydrogen assisted cracking behavior of TRIP-assisted steel

摘要

Notched TRIP tensile samples were strained until fracture and until the tensile strength under variable hydrogen charging conditions in order to assess the influence of hydrogen present in the samples (internal hydrogen) vs. hydrogen charged during tensile testing (environmental hydrogen) on the hydrogen assisted cracking behavior. Three types of charging conditions were applied: 1) pre-charging with hydrogen till saturation followed by tensile testing with in-situ electrochemical hydrogen charging during the test, 2) pre-charging with hydrogen till saturation and tensile testing without additional hydrogen charging during the test, and 3) tensile testing with in-situ electrochemical hydrogen charging, but without pre-charging. Environmental hydrogen was found to embrittle the material more than internal hydrogen, even though less hydrogen was present in the material. Fracture surface and secondary crack analyses indicated the importance of continuous hydrogen supply to critical zones during loading and the importance of the hydrogen/dislocation interaction in the failure process.