Advanced Joining of Single Crystal Aerospace Materials

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The ever-increasing demand for improved gas turbine engine efficiency has driven operating temperatures higher, leading to the use of heat resistant single crystal (SX) Ni-base superalloys and Ni3Al-base intermetallics to manufacture aero-engine turbine components. Joining is not only essential for the fabrication of complex shaped engine components, but it is also crucial for the repair and refurbishment of service-damaged parts. SX Ni-base superalloys and SX Ni3Al-base intermetallics are, however, extremely difficult to join by conventional fusion welding processes due to their high susceptibility to weld cracking. Alternate advanced techniques such as transient-liquid-phase (TLP) bonding hold potential for joining these materials without the problem of cracking. Unfortunately, the commercial use of TLP bonding is currently limited largely due to the inadequate understanding of microstructural development during the bonding of multi-component base-filler alloy systems. The proposed research is aimed at advancing industrial applications of TLP bonding. The applicant proposes to use electron microscopy and spectroscopy techniques and numerical modeling to systematically study, in detail, new effective ways of reducing the processing time that is required to produce stray-grains-free TLP joint in similar and dissimilar SX materials, with the use of multi-component commercial filler alloys. Furthermore, he and his team will develop post-bond thermal treatment scheme to chemically and microstructurally homogenize TLP bonded materials for improved high-temperature properties. The proposed study will significantly advance the current understanding of TLP bonding mechanisms, and provide valuable knowledge vital to effective modeling and optimization of the joining process. Ultimately, the research will contribute to the development of more efficient and reliable procedures for joining advanced SX aerospace materials, thereby enhancing Canada's competitiveness in pioneering advanced joining technology.