High temperature fatigue: behaviour of three typical classes of structural materials

Abstract

The goals of this paper are: (i) to review the mechanisms of cyclic deformation, damage accumulation and crack propagation in three types of materials widely used in power generation industries, i.e. Cr–Mo steels, austenitic stainless steels and superalloys used in jet engine turbines (both Ni base and Fe–Ni base) when they are tested at elevated temperature; (ii) to relate these mechanisms to engineering applications; (iii) to review life prediction methodologies including thermomechanical fatigue (TMF); and (iv) to point out current and likely future trends in the development of more fatigue resistant materials and life prediction methods. The emphasis is laid on the creep–fatigue–oxidation behaviour of the two first classes of materials, i.e. 9–12% martensitic Cr steels and austenitic stainless steels. As the major issue for the design of components used in power generation industries is the extrapolation of short term laboratory data to much longer times, only physically based models for life prediction are examined. In Ni base superalloys, the emphasis is laid on the effect of oxidation on fatigue crack growth rate at elevated temperature and on their behaviour in TMF

Keywords:

• High temperature fatigue
• Hold time effect
• Intergranular damage
• Oxidation effect
• Isothermal and thermomechanical fatigue