The effect of minor elements on the hot-workability of nickel-based superalloys

Source abstract

Abstract We have investigated the effect of five minor elements, S, Ca, Mg, Y and Zr, on the hotworkability of three solid solution strengthened nickel-based superalloys, Inconel 600, Hastelloy-X and a Ni-Cr-W type prospective alloy (NSC-1) for heat exchanger pipes in high temperature gas reactors. The hot-workability was evaluated from the reduction in area of hot tensile specimens by using a Gleeble testing machine. Round bar specimens were prepared from the near-surface portion of the alloy ingots, melted and cast by vacuum induction melting, vacuum arc remelting or electro-slag remelting. When the S content increases, a ductility dip appears between 1050 and 1150 °C on each alloy; the greater the S content, the deeper the dip. At the same time, the fracture appearance becomes more and more intergranular. By adding a small amount of Ca, Mg, Y or Zr, the hot-workability of the alloys changed drastically, and it was found that a controlled addition of these minor elements gave a superior hot ductility