Microstructure and yield strength effects on hydrogen and tritium induced cracking in HERF (high-energy-rate-forged) stainless steel

Conference · Sun Jan 01 00:00:00 EST 1989

OSTI ID:5365938

Morgan, M J; Tosten, M H

Rising-load J-integral measurements and falling-load threshold stress intensity measurements were used to characterize hydrogen and tritium induced cracking in high-energy-rate-forged (HERF) 21-6-9 stainless steel. Samples having yield strengths in the range 517--930 MPa were thermally charged with either hydrogen or tritium and tested at room temperature in either air or high-pressure hydrogen gas. In general, the hydrogen isotopes reduced the fracture toughness by affecting the fracture process. Static recrystallization in the HERF microstructures affected the material's fracture toughness and its relative susceptibility to hydrogen and tritium induced fracture. In hydrogen-exposed samples, the reduction in fracture toughness was primarily dependent on the susceptibility of the microstructure to intergranular fracture and only secondarily affected by strength in the range of 660 to 930 MPa. Transmission-electron microscopy observations revealed that the microstructures least susceptible to hydrogen-induced intergranular cracking contained patches of fully recrystallized grains. These grains are surrounded by highly deformed regions containing a high number density of dislocations. The microstructure can best be characterized as duplex'', with soft recrystallized grains embedded in a hard, deformed matrix. The microstructures most susceptible to hydrogen-induced intergranular fracture showed no well-developed recrystallized grains. The patches of recrystallized grains seemed to act as crack barriers to hydrogen-induced intergranular fracture. In tritium-exposed-and-aged samples, the amount of static recrystallization also affected the fracture toughness properties but to a lesser degree. 7 refs., 25 figs.

• Research Organization: Westinghouse Savannah River Co., Aiken, SC (USA)
• Sponsoring Organization: DOE/DP
• DOE Contract Number: AC09-89SR18035
• OSTI ID: 5365938
• Report Number(s): DP-MS-89-27; CONF-8909204-5; ON: DE90003505
• Resource Relation: Conference: Conference on hydrogen effects on material behavior, Jackson Hole, WY (USA), 12-16 Sep 1989
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
STAINLESS STEELS
CRACK PROPAGATION
DISLOCATIONS
FRACTURES
HYDROGEN EMBRITTLEMENT
MECHANICAL PROPERTIES
MICROSTRUCTURE
PREDICTION EQUATIONS
TRANSMISSION ELECTRON MICROSCOPY
TRITIUM
YIELD STRENGTH
ALLOYS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
ELECTRON MICROSCOPY
EMBRITTLEMENT
EQUATIONS
FAILURES
HIGH ALLOY STEELS
HYDROGEN ISOTOPES
IRON ALLOYS
IRON BASE ALLOYS
ISOTOPES
LIGHT NUCLEI
LINE DEFECTS
MICROSCOPY
NUCLEI
ODD-EVEN NUCLEI
RADIOISOTOPES
STEELS
YEARS LIVING RADIOISOTOPES
360103* - Metals & Alloys- Mechanical Properties
360102 - Metals & Alloys- Structure & Phase Studies
360106 - Metals & Alloys- Radiation Effects