Abstract
Creep behaviour and long-term microstructural stability of cast nickel based superalloy IN 792 5A were studied. This investment cast superalloy fully fulfils current requirements of gas turbine designers of turbine blades and other hot parts of gas turbines and turbochargers. The methodology for evaluation creep characteristics and measured creep properties such as creep strength, creep strength to 1 % strain and minimum creep rates are presented. The microstructure analysis of specimens before and after creep testing showed that the initial microstructure is unstable during long-term creep exposure. Coarsening of cuboidal γ‘ precipitates and the development of rafted structure in some equiaxed grains are quantitatively analysed. The alloy fails by growth and coalescence of cavities and cracks formed at the grain boundaries, interfaces between eutectic regions and the γ/γ‘ matrix and within brittle carbide
particles.

Key words
Ni based superalloy, castings, creep properties, microstructure

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