Joining of Zirconium Alloys to Nickel Bearing Alloys for In-Core Components

Zirconium alloys are well-positioned as the material of choice for nuclear in-core structures since they have a low neutron absorption cross section and possess good material properties under elevated neutron flux and high-temperature operating conditions. The Canadian supercritical water-cooled reactor (SCWR) concept pressure tube includes a transition from zirconium-tin alloy (Excel) to a yet to be selected stainless steel to allow it to be seal welded to the inlet plenum. Thus, a method to join zirconium and its alloys to ferrous and nickel-bearing alloys is desired. To this end, a series of experiments were carried out to demonstrate the feasibility of this method. A joint approaching the strength of the parent material was achieved using both rotary friction welding and co-extrusion methods, although the joints exhibited lower ductility than that of the parent material. Microstructural examination of the joint revealed a ∼200 nm to ∼1 μm intermetallic layer at the transition zone, which was the location of failure in the tensile specimen.