Characterization of Simulated Production Welds in Alloy 908
This study characterized room temperature mechanical properties of Incoloy® alloy 908* welds made from two base metal conditions: mill-annealed or homogenized (1050°C/1hr). An automatic pulsed-gas tungsten arc welder simulated actual conduit welding conditions.
The weld fusion zone showed a typical cellular-dendritic microstructure with the precipitation of secondary phases within the interdendritic zone. Grain boundary liquation phenomenon was observed near the fusion boundaries in the heat affected zone. Complete resolidification of liquated grain boundaries prevented crack formation during welding.
The tensile properties of the welds showed a strong dependence on the selection of the base metal used for welding. When the base metal was homogenized, the welds showed about the same amount of ductility as the homogenized base metal in the as-welded condition. Its strength was also higher than that of the surrounding homogenized base metal. The fracture toughness of welds was measured by the J-integral test technique. Unlike the tensile properties, the fracture toughness of the welds showed no dependence on the condition of the base metal. The fracture toughness of the welds was about 140 MPa√m in the aged condition. The fatigue crack growth rates of aged production welds were comparable to those of the base metal. The fatigue crack growth threshold was measured to be about 3.7 MPa√m for the as-welded production welds with homogenized base metal.
KeywordsFracture Toughness Base Metal Fatigue Crack Growth Fusion Zone Heat Affected Zone
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- 1.D.B. Montgomery, “Preliminary Description of ITER Magnet-Drawing Package,” Trip report to ITER R&D meeting at JET, (1992).Google Scholar
- 2.C.H. Jang, I.S. Hwang, R.G. Ballinger and M.M. Steeves, Adv. Cry. Eng. Mat. 40: 1323 (1994).Google Scholar
- 3.C.H. Jang, Ph.D Thesis, Massachusetts Institute of Technology, (1995).Google Scholar
- 4.D.J. O’lone, M.S. Thesis, Massachusetts Institute of Technology, (1992).Google Scholar
- 5.I.S. Hwang, R.G. Ballinger and C.H. Jang, “Properties of Incoloy 908,” Workshop on structural materials R&D for ITER, Boulder, (1991).Google Scholar
- 6.C.H. Jang, “Alloy 908 Weld Characterization,” U.S. ITER Incoloy 908 workshop, Pacific Grove, (1994).Google Scholar
- 7.M.M. Steeves, private communication (1994).Google Scholar
- 8.J.T. Salkin, “Development of Welding Procedure for Incoloy 908 Superconductor Sheathing”, Job report prepared for Inco Alloys International, Inc., by Arc Application Inc., (1994).Google Scholar
- 9.J.T. Salkin, “Incoloy 908 Test Plates Welded with the Simulated Procedure for Square Sheathing”, Job report prepared for Massachusetts Institute of Technology, by Arc Application Inc., (June 1994).Google Scholar
- 10.J.T. Salkin, “Incoloy 908 Test Plates Welded with the Simulated GTA Procedure for Square Sheathing”, Job Report Prepared for Massachusetts Institute Technology, by Arc Application Inc., (Sept. 1994).Google Scholar
- 11.ASTM Standard E 8–86, “Standard Methods of Tension Testing of Metallic Materials.”Google Scholar
- 12.ASTM Standard E 647–93, “Standard Method for Measurement of Fatigue Crack Growth Rates.”Google Scholar
- 13.W.A. Herman, R.W. Hertzberg, C.H. Newton and R. Jaccard, “Fatigue 87”, R.O. Ritchie and E.A. Starke, Jr. eds., Engineering Materials Advisory Services Ltd., (1987), p. 819.Google Scholar
- 14.R.L. Tobler and I.S. Hwang, Adv. Cry. Eng. Mat. 40: 1315 (1994).Google Scholar
- 15.ASTM Standard E 813–89, “Standard Test Method for JIc, A Measure of Fracture Toughness.”Google Scholar
- 16.ASTM Standard E 1152–87, “Standard Test Method for Determining J-R Curves.”Google Scholar
- 17.S.C. Ernst, W.A. Baeslack III and J.C. Lippold, Welding Journal, p. 418s-430s, (Oct. 1989)Google Scholar
- 19.W.A. Owczarski, “Physical Metallurgy of Metal Joining,” R. Kossowsky and M.E. Glicksman des., The Metallurgical Society of AIME, (1979), p. 166.Google Scholar