Investigation of the thermal stability of a commercial Ni--Cr--Fe--Mo alloy (Hastelloy Alloy X). [538 to 871/sup 0/C]
The changes in hardness and room temperature impact toughness of Hastelloy Alloy X after aging at 1000, 1200, 1400 and 1600/sup 0/F (538, 649, 760 and 871/sup 0/C) for times up to 10,000 hr were investigated. The alloy exhibts age-hardening at 1200 and 1400/sup 0/F (649 and 760/sup 0/C). A slight hardness increase was observed at 1600/sup 0/F (871/sup 0/C) followed by overaging after 4000 h. No age-hardening was observed at 1000/sup 0/F (538/sup 0/C) up to 10,000 h. Aging at all temperatures resulted in a substantial drop in room temperature impact toughness. The microstructure after aging was characterized by optical metallography and x-ray diffraction, while fracture mode was characterized by scanning electron microscopy. The results suggest that the toughness degradation is primarily associated with carbide precipitation. M/sub 6/C' type carbides are believed to be the major phase precipitated during aging at all temperatures, although sigma and ..mu.. phases were also detected after 10,000 h at 1400 and 1600/sup 0/F (760 and 871/sup 0/C), respectively.
- Research Organization:
- General Atomic Co., San Diego, CA
- OSTI ID:
- 6428258
- Journal Information:
- Metall. Trans., A; (United States), Journal Name: Metall. Trans., A; (United States) Vol. 9:6; ISSN MTTAB
- Country of Publication:
- United States
- Language:
- English
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36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
AGE HARDENING
ALLOYS
CARBIDES
CARBON COMPOUNDS
CHROMIUM ALLOYS
COBALT ALLOYS
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
FRACTURE PROPERTIES
GAS COOLED REACTORS
GRAPHITE MODERATED REACTORS
HARDENING
HASTELLOY X
HASTELLOYS
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
HIGH TEMPERATURE
HTGR TYPE REACTORS
IRON ALLOYS
MATERIALS
MECHANICAL PROPERTIES
MICROSTRUCTURE
MOLYBDENUM ALLOYS
NICKEL ALLOYS
PHASE TRANSFORMATIONS
PRECIPITATION
REACTOR COMPONENTS
REACTORS
SEPARATION PROCESSES
STABILITY
STRESSES
THERMAL STRESSES
TUNGSTEN ALLOYS
VERY HIGH TEMPERATURE