Augmented Heating of Dissimilar Metals to Improve Joinability of Friction Welds

All solid-state welding methods employ some variation of heat and deformation to accomplish bonding. Heat and deformation are key to bringing working surfaces into intimate contact, displacing surface oxide-based contaminants, and allowing solid state bonding of the substrates. Friction welding methods accomplish this through relative motion of the materials under force. Implicit in traditional friction welding technology are large variations in shear loads particularly during the initial stages of the process. This load variation is a major consideration for machine robustness, tooling design, process set-up, part design, material selection, and overall cost. As an innovation to reduce these initial process loads, the use of pre-heating has been investigated. The approach enables raising workpiece temperatures to plasticization temperatures in very short times (100’s of milliseconds) and offers a uniform through thickness heating profile. Our Phase I proposal addressed our use of the pre-heat augmented process, and our approach at investigating the capability of modeling the ”Low Force” technology for bonding dissimilar Titanium alloys to be used in blisk production. The goal of Phase II would be to progress to advanced development the Low Force Linear Friction Welding of these dissimilar titanium materials while utilizing process modeling capability. Success will provide the future path for the welding process with other existing and new alloys. The anticipated results of Phase II would include a selection of final process parameters for the materials of study as well as a validated process model which can more accurately predict heat distribution during welding. This ability provides a route for Air Force OEM IBD, engine, and critical flight component manufacturers to bring new and existing components to manufacturability more quickly, with greater accuracy, and at a lower cost than traditional methods. Additional potential benefits may include increases in the strength and durability of the component joint and subsequently the component assembly. Critical to the Phase II plan will be a weld study of comparing traditional linear friction welded coupons to Low Force welded coupons and how a reduction of required process friction power and energy translates to a smaller machine footprint or extended part family machine capability for OEM’s implementing this technology.