Weldability study in dissimilar microwelding of nickel-titanium alloys

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Welding and joining of dissimilar materials, such as Nickel-Titanium (NiTi) alloys to other alloys, remains as one of the main challenges in manufacturing medical devices. The main issue is the formation of intermetallic compounds (IMCs) that is normally detrimental to the joint properties and performance. The current proposal seeks, in collaboration with Baylis Medical, a systematic study of laser dissimilar microwelding of NiTi alloys to Ti alloys or stainless steel for catheter guidewire and other medical device applications aiming to improve understanding of the effects of base metal chemistry and conditions, and laser welding process parameters and configurations on the IMC formation and its influence on mechanical properties. It is especially planned to investigate and develop the use of interlayers to limit IMC formation. While this project will study primarily laser welding, other welding processes such as resistance microwelding will be explored as alternatives to form solid-state welds so IMCs might be completely eliminated. The proposed work would strengthen Canada's position in the fields of design and fabrication of medical devices and other microsystems in general, and advanced materials joining in particular. Specifically, the knowledge and engineering know-how developed in this proposed work will make significant contributions (in terms of journal and conference publications) to the science and technology of dissimilar materials joining. It will also provide engineering guidelines to optimize the process conditions and to increase flexibility for design and fabrication of medical devices. This work will also foster development of welding and joining expertise at different levels (undergraduate and graduate students, and post-doctoral fellows), as needed by manufacturing industries.