The effect of hydrogen on the fracture of alloy X-750

Journal Article · Mon Jan 01 04:00:00 EST 1996 · Metallurgical Transactions, A

DOI:https://doi.org/10.1007/BF02647750· OSTI ID:203521

Symons, D M ^[1]; Thompson, A W ^[2]

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1. Bettis Atomic Power Lab., West Mifflin, PA (United States)
2. Lawrence Berkeley Lab., CA (United States). Materials Science Div.

The effect of hydrogen on the fracture of a nickel-base superalloy, alloy X-750, was investigated in the HTH condition. The effect of hydrogen was examined through tensile testing incorporating observations from scanning electron microscopy and light microscopy. The ductility at 25 C, as measured by elongation to failure for tensile specimens, was reduced from 21 pct for noncharged specimens to 7.3 pct for 5.7 ppm hydrogen and to 3.5 pct for 65 ppm hydrogen. The elongation to failure was a function of the strain rate and test temperature. For hydrogen-charged specimens, the elongation decreased as the strain rate decreased at a constant temperature, while for a constant strain rate and varying temperature, there was a maximum in embrittlement near 25 C and no embrittlement at {minus}196 C. For the noncharged specimens, the elongation monotonically increased as temperature increased, while there was no noticeable effect of strain rate. Prestraining prior to charging dramatically decreased elongation after hydrogen charging. When the strain rate was increased on the prestrained specimens, more plastic deformation was observed prior to failure. Failure did not occur until the flow stress was reached, supporting the proposition that plasticity is required for failure. The intergranular failure mechanism in alloy X-750 was a microvoid initiation process at grain boundary carbides followed by void growth and coalescence. The reduced ductility may be explained by either a reduction of the interfacial strength of the carbide-matrix interface or a local hydrogen pressure at the carbide-matrix interface.

• Sponsoring Organization: USDOE
• DOE Contract Number: AC11-93PN38195
• OSTI ID: 203521
• Journal Information: Metallurgical Transactions, A, Journal Name: Metallurgical Transactions, A Journal Issue: 1 Vol. 27; ISSN MTTABN; ISSN 0360-2133
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
36 MATERIALS SCIENCE
BWR TYPE REACTORS
CARBIDES
CHROMIUM ALLOYS
DUCTILITY
ELONGATION
FLOW STRESS
FRACTURES
GRAIN BOUNDARIES
HYDROGEN
IRON ALLOYS
MATERIALS
METALLURGICAL EFFECTS
NICKEL BASE ALLOYS
OPTICAL MICROSCOPY
PWR TYPE REACTORS
SCANNING ELECTRON MICROSCOPY
STRAIN RATE
TEMPERATURE DEPENDENCE
TENSILE PROPERTIES
VOIDS