An engine block cast from aluminum or magnesium-matrix nanocomposites can be much lighter than one cast from aluminum alone. Similarly, a power-plant pressure vessel made from advanced steel that can withstand higher temperature and pressure without deforming could burn more efficiently and produce less pollution. Researchers continue to create new materials with properties that promise to reduce weight, increase performance and save energy in numerous applications. But in many cases, before these advanced materials can be put to use, someone has to figure out how to weld them.
With funding from the National Science Foundation, Professor Sindo Kou (pictured with graduate student Dustin Wagner) and colleagues from Ohio State, Lehigh University and the Colorado School of Mines have formed the Industry/University Collaborative Research Center for Integrative Materials Joining Science for Energy Applications. The center seeks to extend the service lifetime of welds in the existing energy infrastructure, increase the efficiency of advanced welding materials, and create the technologies required to join those materials for use in new infrastructure.
Industry partners such as Hobart Brothers, Cummins and NASA have joined the center to explore options for creating or improving new joining science. Hobart Brothers is working with Kou to develop new welding filler wires that will make welds not only resistant to creep (deformation at high temperatures) but also tough enough to resist cracking when the pressure vessel is cooled down. Cummins is working with Mechanical Engineering Professor Xiaochun Li, the associate center director, on the weldability of cast metal-matrix nanocomposites for engines. Arc welding is routinely used to repair cracks and surface defects of metal castings, but metal-matrix nanocomposites are so new, no one has devised a method to weld them.
NASA seeks to weld metals by traversing a rotating rod along the joint between two plates that are held tight together under thousands of pounds of pressure and softened in the area ahead of the rod by localized heating. The heating prevents the rod from wearing out. The pressure and heat create atomic-level contact between the metals, and they form new bonds, or weld, without melting. The process, called thermal-stir welding (as opposed to friction-stir welding), has been used successfully with titanium alloys. Now, NASA will work with Kou’s team to apply it to energy-related materials.