Solid State and Resistance Joining Technologies for Fusion Energy Systems

75673-The development of fusion power plants requires the design, development and qualification of structural materials for first wall/breeding blanket systems that can withstand long-term exposure to the hostile fusion environment. This environment includes high-energy neutrons, neutral and charged plasma particles, and high surface heat fluxes. Nanocomposite, oxide dispersion strengthened (ODS) ferritic alloys that possess excellent resistance to high temperature thermal aging, neutron irradiation damage, and high-temperature creep are currently being considered as primary structural materials for these first wall/blanket systems. However, the application of these materials requires the development of advanced joining technologies that retain properties (nanostructures) similar to those of base materials. The challenge is to minimize the coarsening of the strengthening dispersoids, because the coarsening can result in reduced in creep strength. Conventional fusion welding processes cannot be used for joining ODS ferritic alloys because they result in distortion, steep residual stress fields, and coarsening of the strengthening dispersoids. Therefore, this project will demonstrate advanced solid-state and resistance joining technologies that will enable the use of nanocomposite ODS ferritic alloys as fusion reactor first wall/blanket structural components. Phase I will demonstrate two joining processes, Friction Stir Welding and ElectroSpark Discharge, using ODS ferritic alloy test specimens; determine the suitability of the joining processes for use in first wall/blanket applications; and prepare a detailed test plan for Phase II demonstrations. Commercial Applications and Other Benefits as described by the awardee: Many existing industries could benefit from the application of solid-state and resistance joining processes to nanocomposite ODS ferritic alloys. Specific applications include petrochemical and chemical plants, gas turbine engineering industries, aircraft and aerospace industries, electrical power plants, large fossil-fired power plants, and nuclear fission plants. In addition, the military sector could use the joining technologies to produce superior welds in the hull structures and power plants of surface ships and submarines.