Irradiation-assisted stress corrosion cracking of HTH Alloy X-750 and Alloy 625

Conference · Sat Jul 01 04:00:00 EDT 1995

OSTI ID:81972

Bajaj, R; Mills, W J; Lebo, M R; Hyatt, B Z; Burke, M G

In-reactor testing of bolt-loaded compact tension specimens was performed in 360 C water. New data confirms previous results that high irradiation levels reduce SCC resistance in Alloy X-750. Low boron heats show improved IASCC (irradiation-assisted stress corrosion cracking). Alloy 625 is resistant to IASCC. Microstructural, microchemical, and deformation studies were carried out. Irradiation of X-750 caused significant strengthening and ductility loss associated with formation of cavities and dislocation loops. High irradiation did not cause segregation in X-750. Irradiation of 625 resulted in formation of small dislocation loops and a fine body-centered-orthorhombic phase. The strengthening due to loops and precipitates was apparently offset in 625 by partial dissolution of {gamma} precipitates. Transmutation of boron to helium at grain boundaries, coupled with matrix strengthening, is believed to be responsible for IASCC in X-750, and the absence of these two effects results in superior IASCC resistance in 625.

• Research Organization: Westinghouse Electric Corp., West Mifflin, PA (United States). Bettis Atomic Power Lab.
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC11-93PN38195
• OSTI ID: 81972
• Report Number(s): WAPD-T--3054; CONF-950816--1; ON: DE95014553
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BORON ADDITIONS
CRACKS
FASTENERS
INCONEL 625
INCONEL X750
NEUTRON FLUENCE
PHYSICAL RADIATION EFFECTS
STRESS CORROSION