Effect of dopant element on the strength and reliability of ni-base superalloy at high tempera tures

In order to assure the reliability of advanced gas turbine systems, it is very important to evaluate the damage of high temperature materials such as Ni-base superalloys under creep and fatigue conditions quantitatively. The mechanism of the directional coarsening (rafting) of the ' phase (Ni 3 Al) of Ni- base superalloys under uni-axial strain at high temperatures was analyzed by molecular dynamics (MD) analysis. The strain-induced anisotropic diffusion of Al atoms perpendicular to the interface between the ' phase and the phase (Ni- matrix) was observed clearly at a Ni(001)/Ni 3 Al(001) interface. The strain-induced anisotropic diffusion was validated by the experiment using the stacked thin film structures with the (001) face-centered cubic (FCC) interface. The reduction of the diffusion of Al atoms perpendicular to the interface is thus, effective for improving the creep and fatigue resistance of the alloy. It was found by MD analysis that palladium was one of the most effective elements that restrain Al atoms from moving around the interface under the applied stress. The presence of the interaction between the different dopant elements was also clarified.