Mechanical and microstructural assessments of RR1000 to IN718 inertia welds - effects of welding parameters

In the present study inertia friction welded RR1000 to IN718 joints have been investigated. Crack growth tests within 0.3 mm of the weld interface, conducted in air at 500 and 650 degrees C, have shown that there is no difference in crack growth rate due to three different sets of welding parameters applied. The cracks were found to propagate from RR1000 through the weld line into IN718. In RR1000 the cracks pass a zone within 15-30 mu m from the weld interface, allowing higher crack growth rates. Fractographic studies have shown that these higher crack growth rates are caused by a higher tendency to intergranular cracking, most likely due to oxidation damage along grain boundaries. The similar properties of the welds tested can be related to a similar weld process characteristic during the last second of the welding cycle for all three sets of welding parameters applied.