Welding of Single and Polycrystal Nickel Superalloys to Aluminides Based Aero-engine and Power Generation Turbine Materials by New and Emerging Joining Technologies

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Conventional high-temperature superalloys used in aero-engine turbines have reached their upper temperature application limit, and TiAl and Ni3Al based alloys with a higher high temperature capability are being developed. Their use would require them to be welded to fabricate and repair aero-turbine components. These materials would also need to be joined to conventional Ni superalloys. Both, Ni superalloys and Intermetallic alloys are extremely difficult to weld, but joining them together becomes even more challenging due to a significant disparity in their chemistry and microstructure. Therefore, the LONG-TERM objective of the proposed research is to obtain a basic knowledge of the science and technology of joining of current and new generation aluminide based aero-turbine materials using emerging welding processes to develop reliable joining procedures. In the SHORT-TERM the research will investigate the weld cracking issues during welding of polycrystalline IN 738 and single crystal CSMX 486 Ni superalloys to single crystal NI3AL based alloy IC 6, and develop methods to produce crack-free welds. This will be achieved through welding experiments using various filler alloys and pre and post-weld heating during laser welding, laser-arc hybrid welding and linear friction welding using various process parameters. As in the past, the welding experiments will be performed at Standard Aero. Inc. Winnipeg, and NRC Aerospace Manufacturing Technology Centre, Montreal. Weld cracking and microstructures of the welds will be evaluated, by state-of-the-art microstructure characterization facilities available in applicant's laboratory, to determine the role of process parameters and filler alloy composition on quality of welds. Process parameters and filler alloy compositions will then be optimized through numerical modeling, and the developed model will be validated by further experimentation. It is planned to train 2 M.Sc. and 2 PhD students through the proposed research. This research will help develop welding procedures for Ni and Ti aluminide based emerging aero-turbine materials, and help enhance Canadian Aerospace companies' competitive position in the world markets.