Solidification and weldability of Nb-bearing superalloys
- Lehigh Univ., Bethlehem, PA (United States)
- Sandia National Labs., Albuquerque, NM (United States)
The solidification and weldability of experimental superalloys containing systematic variations in Fe, Nb, Si and C were studied using differential thermal analysis (DTA), microstructural characterization techniques and Varestraint testing. Microstructural evolution during solidification of DTA samples and gas tungsten arc welds generally occurred by a three-step solidification process. Solidification initiated by a primary L {yields} {gamma} reaction, which enriches the interdendritic liquid in Nb and C until a eutectic-type L {yields} ({gamma} + NbC) reaction occurs over a rather broad temperature range. Solidification terminated by a second eutectic-type reaction, L {yields} ({gamma} + Lave), which occurred over a narrow temperature range. Carbon additions increased the start temperature of the L {yields} ({gamma} + NbC) reaction and induced a concomitant decrease in the temperature interval of the primary L {yields} {gamma} stage of solidification. As a result, carbon additions often promoted a significant improvement in solidification cracking resistance. The results from solidification studies are combined with detailed examinations of microstructural morphologies in fusion zone solidification cracks to propose a microstructure morphology classification scheme.
- Research Organization:
- Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 655470
- Journal Information:
- Welding Journal, Vol. 77, Issue 10; Other Information: PBD: Oct 1998
- Country of Publication:
- United States
- Language:
- English
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