The effect of thermal treatment on the fracture properties of alloy X-750 in aqueous environments

Technical Report · Sat May 01 00:00:00 EDT 1993

OSTI ID:10172837

Ballinger, R; Elliott, C S; Hwang, I S; Prybylowski, J ^[1]

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1. Massachusetts Inst. of Tech., Cambridge, MA (United States)

Alloy X-750 is a high strength, age hardenable nickel-base alloy used in light water nuclear reactors. The excellent corrosion resistance and high temperature strength of alloy X-750 make it suitable for use in a variety of structure components in both pressurized water reactors and boiling water reactors. These applications involve exposure of highly stressed material to aqueous media. Operational stresses are subject to low frequency thermally induced fluctuations and high frequency flow induced fluctuations. In general, alloy X-750 has performed well in light water reactors. However, an economically significant number of components have failed unexpectedly due to localized forms of attack such as corrosion fatigue and stress corrosion cracking. Thermal processing history is known to play a significant role in the fracture properties of alloy X-750 in aqueous environments. While thermal treatments have been developed recently to improve performance, in many cases the reason for improved performance remains unclear. Therefore, identification of the mechanisms responsible for the degradation of fracture properties in aqueous environments is necessary. As a corollary it is necessary to achieve an understanding of how thermal treatment influences microstructure and, in turn, how microstructure influences fracture properties in aqueous environments. This report discusses five thermal treatments which were studied: (1) SA-1 hr at 1093{degree}C, (2) AH - 24 hr at 885{degree}C + 20 hr at 704{degree}C, (3) HTH - 1 hr at 1093{degree}C + 20 hr at 704{degree}C, (4) AHTH - 1 hr at 1093{degree}C + 24 hr at 885{degree}C + 20 hr at 704{degree}C, and (5) HOA - 1 hr at 1093{degree}C + 100 hrs at 760{degree}C. Microstructural characterization of these materials was accomplished through the use of optical microscopy, transmission electron microscopy,scanning transmission electron microscopy, energy dispersive x-ray spectroscopy, and x-ray diffractometry.

• Research Organization: Electric Power Research Inst., Palo Alto, CA (United States); Massachusetts Inst. of Tech., Cambridge, MA (United States)
• Sponsoring Organization: Electric Power Research Inst., Palo Alto, CA (United States)
• OSTI ID: 10172837
• Report Number(s): EPRI-TR-102437; ON: UN93016656; TRN: 93:016600
• Resource Relation: Other Information: PBD: May 1993
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
36 MATERIALS SCIENCE
NICKEL BASE ALLOYS
FRACTURE PROPERTIES
HEAT TREATMENTS
WATER COOLED REACTORS
REACTOR COMPONENTS
MICROSTRUCTURE
EMBRITTLEMENT
CORROSION
AQUEOUS SOLUTIONS
GRAIN BOUNDARIES
TEMPERATURE DEPENDENCE
220200
360103
COMPONENTS AND ACCESSORIES
MECHANICAL PROPERTIES