Weld Solidification Cracking in Solid-Solution Strengthened Ni-Base Filler Metals
The weld solidification cracking susceptibility of several solid-solution strengthened Ni-base filler metals was evaluated using the transverse Varestraint test. The alloys tested included Inconel 617, Inconel 625, Hastelloy X, Hastelloy W, and Haynes 230
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The Ohio State University, Columbus, Ohio, USA Brazilian Synchrotron Light Laboratory, Campinas-SP, Brazil
Abstract The weld solidification cracking susceptibility of several solid-solution strengthened Ni-base filler metals was evaluated using the transverse Varestraint test. The alloys tested included Inconel 617, Inconel 625, Hastelloy X, Hastelloy W, and Haynes 230W.* Susceptibility was quantified by determining the solidification cracking temperature range (SCTR) which is a direct measurement of the range over which cracking occurs. This temperature range was then compared to the equilibrium solidification temperature range derived from Calphad-based ThermoCalc™ calculations, Scheil-Gulliver solidification simulations, and in-situ measurements using the single sensor differential thermal analysis (SS-DTA) technique. Good correlation among the simulated and measured solidification temperature ranges, and SCTR values were found for the 617 and 230W filler metals. These two filler metals exhibited the best resistance to weld solidification cracking. Correlation among measured and simulated temperature ranges, and SCTR was poor for Hastelloy alloys X and W. Alloy 625 was found to be the most susceptible to solidification cracking, but this result is in conflict with fabrication experience. This appears to be the result of the inability of the Varestraint test to account for crack “healing” during the final stages of solidification.
Inconel® is a registered trademark of Special Metals Company, a PCC company. Hastelloy® is a registered trademark of Haynes International. In this paper, a shortened version of these alloys will be used that does not include the trademark. *
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J.C. Lippold et al.
Introduction Solid-solution strengthened Ni-base alloys are used in applications where moderate strength and excellent corrosion resistance are required. Nickelbased alloys are widely used in a variety of industries, including pulp and paper, power generation, chemical handling and processing, coal gasification and liquefaction, and turbine engines. In all these industries, the combination of mechanical properties and corrosion resistance of these alloys are required to meet demanding service conditions. In welded fabrication, one problem that is often encountered with these alloys is weld solidification cracking. Since the Ni-base alloys are austenitic, and solidify as a face centered cubic (FCC) gamma phase, they are inherently susceptible to weld solidification cracking. This form of cracking occurs along solidification grain boundaries in the weld metal due to the presence of liquid films at the boundary at the end of solidification. In this investigation, the susceptibility to weld solidification cracking was quantified using the transverse Varestraint test. The solidification behavior was evaluated using a combination of computational and experimental techniques. A comparison between solidification temperature range and cracking susceptibility measured using the Varestraint test was then conducted. The Varestraint
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