BS in Materials Engineering
Materials Engineering Department
Abbott Vascular manufactures medical guide wires that consist of 304 stainless steel wire joined to superelastic nickel titanium (Nitinol) wire by a solid-state resistance butt welding process. The objective of this project was to develop a deeper understanding of the mechanical properties of the welds in the guide wires. The wires tested were manufactured using two different processes and then ground to various diameters in the weld region. Vickers microhardness measurements were collected in the longitudinal direction across the heat-affected zones of the welds, as well as the transverse direction across the diameters of the welds. Micrographs of the welds produced by each of the two processes were generated in order to develop a fuller understanding of the where the indentations were relative to the flow of the welds. Wires with 304 stainless steel - Nitinol (NiTi) joints were tensile tested to determine if process type and grind diameter have affect ultimate tensile strength. Wires welded using Process A and ground to 0.0125" had a mean ultimate tensile strength of 192.11ksi, whereas these wires ground to 0.0055" had a mean ultimate tensile strength of 174.68ksi. Wires welded using Process B and ground to 0.0125" had a mean ultimate tensile strength of 179.79ksi, whereas Process B wires ground to 0.0055" had a mean ultimate tensile strength 158.47ksi. Analysis shows that process type and grind diameter independently affect the mechanical properties of the welded joints in the guide wires.
Available for download on Monday, June 07, 2021