| Abstract Scope |
Creep governs the service lives of critical high temperature components like single crystal Ni-base superalloy (SX) first stage blades in gas turbines for aero engines and power plants. Creep shows a strong stress and temperature dependence and one must understand the elementary processes which govern creep in order to safely design and operate high temperature systems. Creep is generally subdivided into periods of primary, secondary and tertiary creep, where creep rates decrease, reach one creep rate minimum and then increase towards final rupture. However, in the low temperature and high stress creep regime of SX (for SX: temperature < 800°C, stress > 600 MPa) two creep rate minima can be distinguished, a first after about 0.5% and a second after 5% strain. High resolution miniature specimen creep testing, analytical transmission electron microscopy and 2D discrete dislocation modelling are combined to identify the elementary processes which govern double minimum creep. |