The effect of carbide precipitation on the hydrogen-enhanced fracture behavior of alloy 690

Journal Article · Wed Apr 01 04:00:00 EST 1998 · Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science

DOI:https://doi.org/10.1007/s11661-998-0253-4· OSTI ID:616501

Symons, D M ^[1]

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1. Bettis Atomic Power Lab., West Mifflin, PA (United States)

Alloy 690 is susceptible to hydrogen embrittlement where hydrogen reduces the ductility and causes the fracture morphology to change to predominantly intergranular. The role of carbide precipitation in the embrittlement behavior is not well defined. The objective of this work is to understand the effect of intergranular carbide precipitation on the hydrogen embrittlement of alloy 690. The work reported herein used tensile and compact-tension specimens in both the solution-annealed condition (minimal grain-boundary carbide precipitation) and in the solution-annealed condition followed by an aging treatment to precipitate grain-boundary carbides. By performing the mechanical tests on materials in both uncharged and hydrogen-charged conditions, it was possible to evaluate the degree of embrittlement as a function of the carbide precipitation. It is shown that the embrittlement due to hydrogen increased as the material was aged to allow grain-boundary carbide precipitation. It is proposed that the increase in embrittlement was caused by increased hydrogen at the carbide/matrix interface due to the trapping and increased stresses at the precipitate interface, which developed from strain incompatibility of the precipitate with the matrix. It is further shown that increasing the hydrostatic stress increased the tendency for intergranular fracture, as is consistent with other nickel-base alloys.

• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC11-93PN38195
• OSTI ID: 616501
• Journal Information: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Journal Name: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science Journal Issue: 4 Vol. 29; ISSN MMTAEB; ISSN 1073-5623
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
HYDROGEN EMBRITTLEMENT
INCONEL 690
MICROSTRUCTURE
PRECIPITATION
STRESSES