solid-state precipitation due to the decreased solubility of Si in nickel at lower temperatures. Unlike the intermetallic phases formed during athermal solidification, which formed interlinked networks, the isolated Ni3Si precipitates would not be expected to have a detrimental effect on joint mechanical strength. 4) Extensive Cr-Mo-Nb-rich boride precipitates were formed in the substrate region due to boron diffusion into the base metal during the brazing process. The formation of these precipitates in the DAZ can affect the local corrosion behavior and aging response of the alloy. 5) Mechanical strength of the joint depends on the microstructure development in the joint region, which in turn is controlled by brazing time. In situations where the brazing time is insufficient to achieve complete isothermal solidification, the fracture occurs via crack propagation through the hard and brittle eutectic type microconstituents in the joint centerline. An inverse relation between width of the ASZ and mechanical properties in terms of shear strength, fracture strain, and fracture energy is established. Completion of isothermal solidification, which resulted in a eutectic-free joint centerline improved the mechanical properties of the bonds. Acknowledgment One of the authors, M. Pouranvari, gratefully acknowledges the support from Prof. H. N. Han during his sabbatical leave in Department of Materials Science & Engineering, Seoul National University. References 1. Rivaux, B., Cao, X., Jahazi, M., Cuddy, J., and Birur, A. 2009. Effect of pre- and post-weld heat treatment on metallurgical and tensile properties of Inconel 718 alloy butt joints welded using 4 kW Nd:YAG laser. J Mater Sci 44: 4557–4571. 2. Yeh, A. C., Lu, K. W., Kuo, C. M., Bor, H. Y., and Wei, C. N. 2011. Effect of serrated grain boundaries on the creep property of Inconel 718 superalloy. Mater. Sci. Eng. A 530: 525–529. 3. Pouranvari, M., Ekrami, A., and Ekrami, A. H. 2008. Microstructure development during transient liquid phase bonding of GTD-111 nickel-based superalloy. J Alloys Comp 461: 641–647. 4. Matthij, J. H. G. 1985. Role of brazing in repair of superalloy components — Advantages and limitations. Mater. Sci. Technol. 1: 608–612. 5. Rabinkin, A. 2004. Brazing with (NiCo Cr)-B-Si amorphous brazing filler metals: Alloys, processing, joint structure, properties, applications. Sci. Technol. Weld. Joining 9: 181–199. 6. Tung, S. K., Lim, L. C., and Lai, M. O. 1996. Solidification phenomena in nickel base brazes containing boron and silicon. Scripta Mater. 34: 125–133. 7. Philips, N. R., Levi, C. G., and Evans A. G. 2008. Mechanisms of microstructure evolution in an austenitic stainless steel bond generated using a quaternary braze alloy. Metall Mater Trans A 39(1): 142–9. 8. Sakamoto, A., Fujiwara, C., Hattori, T., and Sakai, S. 1989. Optimizing processing variables in high-temperature brazing with nickelbased filler metals. Welding Journal 68(3): 63– 71. 9. Arafin, M. A., Medraj, M., Turner, D. P., and Bocher, P. 2007. Transient liquid phase bonding of Inconel 718 and Inconel 625 with BNi-2: Modeling and experimental investigations. Mater. Sci. Eng. A 447: 125–133. 10. Pouranvari, M., Ekrami, A., and Kokabi, A. H. 2008. Microstructure-properties relationship of TLP-bonded GTD-111 nickel-base superalloy. Mater Sci Eng A 490: 229–234. 11. Ojo, O. A., Richards, N. L., and Charturvedi, M. C. 2004. Effect of gap size and process parameters on diffusion brazing of Inconel 738. Sci. Technol. Weld. Joining 9: 209– 220. 12. Duvall, D. S., Owczarski, W. A., and Paulonis, D. F. 1974. TLP Bonding: A new method for joining heat resistant alloys. Welding Journal 53(4): 203–214. 13. Thambury, R., Wallace, W., and Goldak, J. A. 1983. Post weld heat treatment cracking in superalloys. Int. Met. Rev. 28: 1–22. 14. Richards, N. L., Huang X., and Chaturvedi, M. C. 1992. Heat affected zone cracking in cast Inconel 718. Mater Charact 28: 179–87. 15. Radhakrishna, C. H., and Rao, K. P. 1997. The formation and control of Laves phase in superalloy 718 welds. J Mater. Sci. 32 (8): 1977–1984. 16. Ram, G. D. J., Reddy, A. V., Rao, K. P., and Reddy, G. M. 2004. Control of Laves phase in Inconel 718 GTA welds with current pulsing. Sci. Technol.Weld. Joining 9: 390–398. 17. Pouranvari, M., Ekrami, A., and Kokabi, A. H. 2009. Effect of bonding temperature on microstructure development during TLP bonding of a nickel base superalloy. J Alloys Comp 469: 270–275. 18. Gale, W. F., and Butts, D. A. 2004. Transient liquid phase bonding. Sci. Technol. Weld. Joining 9: 283–300. 19. Idowu, O. A., Ojo, O. A., and Chaturvedi, M. C. 2006. Microstructural study of transient liquid phase bonded cast Inconel 738LC superalloy. Metall. Matter. Trans A 37: 2787–96. 20. Idowu, O. A., Richards, N. L., and Chaturvedi, M. C. 2005. Effect of bonding temperature on isothermal solidification rate during transient liquid phase bonding of Inconel 738LC superalloy. Mater. Sci. Eng. A 397: 98– 112. 21. Pouranvari, M., Ekrami, A., and Kokabi A. H. 2008. Microstructure-properties relationship of TLP-bonded GTD-111 nickel-base superalloy. Materials Science and Engineering A 490: 229–234. 22. Butts, D. A. 2005. Transient liquid phase bonding of a third generation gamma-titanimum aluminium alloy-Gamma Met PX. PhD thesis. Auburn University, Auburn, Ala. 23. Cieslak, M. J., Stephens, J. J., and Carr, M. J. 1988. A study of the weldability and weld related microstructure of Cabot Alloy 214. Metall. Matter. Trans A 19A: 657–667. 24. Ojo, O. A., Richards, N. L., and Chaturvedi, M. C. 2004. Microstructural study of weld fusion zone of TIG welded IN 738LC nickel-based superalloy. Scripta Mater 51: 683–688. 25. Cieslak, M. J., Headley, T. J., Knorovsky, G. A., Romig, A. D., and Kollie, T. 1990. A comparison of the solidification behavior of Incoloy 909 and Inconel 718. Metall Mater Trans A 21: 479–88. 26. Knorovsky, G. A., Cieslak, M. J., Headley, T. J., Roming, A. D. Jr., and Hammetter, W. E. 1989. Inconel 718 A solidification diagram. Metall Mater Trans A 20: 2149–2158. 27. Nakao, Y., and Shinozaki, K. 1990. Proceedings of International Conference on High Temperature Materials, Belgium, p. 24. 28. Massalski, T. B. (ed.). 1986. Binary alloy phase diagrams. Metals Park, Ohio: ASM International. 29. Gale, W. F., and Wallach, E. R. 1991. Microstructural development in transient liquidphase bonding. Metall. Trans. A 22: 2451–2457. 30. Alam, T., Chaturvedi, M., Ringer, S. P., and Cairney, J. M. 2010. Precipitation and clustering in the early stages of ageing in Inconel 718. Mater Sci Eng A 527: 7770–7774. 31. Pouranvari, M., Ekrami, A., and Kokabi, A. H. 2013. Solidification and solid state phenomena during TLP bonding of IN718 using ternary Ni-Si-B filler alloy. Journal of Alloys and Compounds 563: 143–149. 32. Pouranvari, M., Ekrami, A., and Kokabi, A. H. 2013. Phase transformation during diffusion brazing of IN718/Ni-Cr-B/IN718. Materials Science and Technology 29: 980–984. 33. Pouranvari, M., Ekrami, A., and Kokabi, A. H. 2013. Transient liquid phase bonding of wrought IN718 nickel based superalloy using standard heat treatment cycles: Microstructure and mechanical properties. Materials and Design 50: 694–701. FEBRUARY 2014, VOL. 93 68-s WELDING RESEARCH
Welding Journal | February 2014
To see the actual publication please follow the link above