Abstract
INCOLOY® alloy 908 is a controlled thermal expansion precipitation hardenable Ni-Fe superalloy having outstanding cryogenic properties to 4 K. The alloy was developed for Nb3Sn 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°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 Nb3Sn reaction heat treatments.
This is a preview of subscription content, log in via an institution.
Buying options
Tax calculation will be finalised at checkout
Purchases are for personal use only
Learn about institutional subscriptionsPreview
Unable to display preview. Download preview PDF.
References
R.G. Ballinger, D.F. Smith, and B.L. Lake, U.S. Patent No. 4, 785, 142, November 15, 1986.
M.M. Morra, R.G. Ballinger, J.L. Martin, M.O. Hoenig, and M.M. Steeves, INCOLOY 9XA, a new low coefficient of thermal expansion sheathing alloy for use in ICCS magnets, “Advances in Cryogenic Engineering,” 34: 157–164 (1987).
M.M. Morra, R.G. Ballinger, and I.S. Hwang, INCOLOY 908, a low coefficient of expansion alloy for high strength cryogenic applications: part I. physical metallurgy, Metallurgical Transactions A, 23A: 317–3192 (December 1992).
L.S. Toma, M.M. Steeves, and R.P. Reed, “INCOLOY alloy 908 Data Handbook,” Massachusetts Institute of Technology, PFCC/RR-94–2 (March 1994).
R.L. Tobler, Cryogenic mechanical properties and fracture mechanics of alloy 908, Proceedings U.S. ITER INCOLOY alloy 908 Workshop, 17–1 to 17–29 (1994).
A. Nyilas, J. Zhang, B. Obst, and A. Ulbricht, Fatigue and fatigue crack growth properties of 316LN and INCOLOY 908 below 10 K, “Advances in Cryogenic Engineering,” 38: 133–140 (1992).
K. Sadananda and P. Shahinian, High-temperature time-dependent crack growth, Micro- and Macro-Mechanics of Crack Growth, Met. Soc. of AIME, 119–130 (1981).
K. Sadananda and P. Shahinian, Creep crack growth in alloy 718, Metallurgical Transactions A, Vol. 8A: 439–449 (March 1977).
S. Floreen, The creep fracture of wrought nickel-base alloys by a fracture mechanics approach, Metallurgical Transactions A, 6A: 1741–1749 (September 1975).
J.M. Larson and S. Floreen, Metallurgical factors affecting the crack growth resistance of a superalloy, Metallurgical Transactions A, 8A: 51–55 (January 1977).
K.J. Hsia, A.S. Argon, and D.M. Parks, Dominant creep failure process in tensile components, Transactions of the ASME Journal of Engineering Materials and Technology, 114: 255–264 (July 1992).
M.M. Morra, Stress Accelerated Grain Boundary Oxidation of INCOLOY alloy 908 in High Temperature Oxygenous Atmospheres, Doctoral thesis, Massachusetts Institute of Technology (1995).
G. Sachs and G. Espey, A new method for determination of stress distribution in thin-walled tubing, Trans. AIME, 147: 348–360 (1942).
J.S. Smith, Controlling elevated temperature oxygen-assisted embrittlement of INCOLOY alloy 908 for Nb3Sn C-I-C sheathing applications, Proceedings U.S. ITER INCOLOY alloy 908 Workshop, 11–3–1 to 11–3–16(1994).
J.H. Schultz, Deoxidation of internal conduit helium during heat treatment, TPX no. 1314–950418-MIT-J Schultz-01, presented at TPX Conduit Material Manufacturing Risk Assessment at PPPL (April 1995).
M.M. Steeves, T.A. Painter, M. Takayasu, R.N. Randall, J.E. Tracey, I.S. Hwang, and M.O. Hoenig, The US demonstration poloidal coil, IEEE Trans. Mag., 27: 2369–2372 (March 1991).
L.S. Toma, I.S. Hwang, M.M. Steeves, and R.N. Randall, Thermomechanical process effects on hardness and grain size in INCOLOY alloy 908, “Advances in Cryogenic Engineering,” 40B: 1307–1314 (1994).
Author information
Authors and Affiliations
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 1996 Springer Science+Business Media New York
About this chapter
Cite this chapter
Smith, J.S., Weber, J.H., Sizek, H.W. (1996). Control of Stress-Accelerated Oxygen-Assisted Cracking of INCOLOY® Alloy 908 Sheath for Nb3Sn Cable-in-Conduit. In: Summers, L.T. (eds) Advances in Cryogenic Engineering Materials . Advances in Cryogenic Engineering Materials , vol 42. Springer, Boston, MA. https://doi.org/10.1007/978-1-4757-9059-7_54
Download citation
DOI: https://doi.org/10.1007/978-1-4757-9059-7_54
Publisher Name: Springer, Boston, MA
Print ISBN: 978-1-4757-9061-0
Online ISBN: 978-1-4757-9059-7
eBook Packages: Springer Book Archive