Control of stress-accelerated oxygen-assisted cracking of INCOLOY{reg_sign} alloy 908 sheath for Nb{sub 3}Sn cable-in-conduit

Journal Article · Sun Jun 01 04:00:00 EDT 1997 · Advances in Cryogenic Engineering

OSTI ID:476730

Smith, J S; Weber, J H; Sizek, H W ^[1]

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1. Inco Alloys International, Inc., Huntington, WV (United States)

INCOLOY{reg_sign} alloy 908 is a controlled thermal expansion precipitation hardenable Ni-Fe superalloy having outstanding cryogenic properties to 4 K. The alloy was developed for Nb{sub 3}Sn cable-in-conduit sheathing and other cryogenic applications and has been specified for the ITER model superconducting magnet coils. INCOLOY alloy 908, like other superalloys, exhibits intergranular cracking under certain combinations of environment, stress, and material heat treatment conditions. For example, cracking may occur while material is exposed in air at temperatures between about 500 and 800{degrees}C if the total tensile stress is greater than some threshold tensile stress. This mechanism, known as stress-accelerated grain boundary oxygen-assisted cracking (or SAGBO), is analogous to intergranular stress corrosion cracking. INCOLOY alloy 908 SAGBO behavior is discussed in the general context of other superalloys. Using a variety of test methods, we examine the SAGBO characteristics under varying environmental-stress conditions. Some practical methods are available to eliminate or minimize SAGBO cracking in Nb{sub 3}Sn reaction heat treatments.

• OSTI ID: 476730
• Report Number(s): CONF-950722--
• Journal Information: Advances in Cryogenic Engineering, Journal Name: Advances in Cryogenic Engineering Vol. 42A; ISSN 0065-2482; ISSN ACYEAC
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
66 PHYSICS
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
CRACK PROPAGATION
INCOLOY ALLOYS
ITER TOKAMAK
OXIDATION
RUPTURES
STRESS CORROSION
SUPERCONDUCTING MAGNETS
TEMPERATURE RANGE 0000-0013 K