Effect of composition and heat treatment cycles on the repair weldability of Alloy 718

Cast and wrought heats of Alloy 718 were produced with three levels of niobium and boron. These heats were then subjected to 0, 5, 20, and 40 heat treatment cycles consisting of both solution and aging treatments. The heat treatments simulated the effect of multiple repair events. Weldability of the materials was assessed by hot ductility and varestraint testing to determine the effect of the composition and heat treatment variations. Among the wrought materials, the low niobium and boron content heat exhibited the best performance in the hot ductility and varestraint tests. The weldability of the cast material was demonstrated to be reduced compared to the wrought material. Increased heat treatment cycles reduced the hot ductility for cast materials having medium and high contents of niobium and boron. The amount of delta phase was noted to increase with the number of heat treatment cycles. Heat treated material was given a final rejuvenation treatment to reduce the amount of delta phase. This treatment resulted in a decrease in weldability based on hot ductility data.