Hot ductility behavior of AD730™ nickel-base superalloy
Résumé
Hot ductility of the newly developed AD730™ nickel-base superalloy was investigated in the temperature interval 1050–1240 °C. The nil strength and nil ductility temperatures were determined by hot tensile testing using the Gleeble™ 3800 weld thermal simulation method. The influence of heating rate, representing the weld thermal cycle, on hot ductility behavior of the alloy was also investigated. The microstructure and the fracture mode of samples were examined by optical and scanning electron microscopy. The influence of heating rate on the extent of grain boundary liquation and void formation was determined and it is shown that the significant ductility loss near the NDT point could be related to the reduction of surface tension at the grain boundary-matrix interface. In addition, the contribution of hard precipitates, such as grain boundary MC carbides, voids, and cavities as other damage mechanisms responsible for ductility loss at high temperature, are discussed.