Low cycle fatigue of alloys in hot section components: progress in life assessment

Hot section components are exposed to high temperature operation and thermal transients during service life. The research of improved performances leads to consider the risk of crack initiation due to isothermal (LCF) or thermal-mechanical (TMF) low cycle fatigue loading in component design. This article gives a short survey of progress in LCF and TMF life estimation procedures due to the description of metallic alloys behavior (superalloys, cast iron, stainless steels). Assessing the lifetime under cyclic loading conditions requires constitutive models accounting for viscoplasticity at service temperatures or during transients. These models can be validated at the laboratory scale using thermal mechanical fatigue tests. Crack initiation life prediction models can be quite simple or need to account for creep-fatigue interactions or environmental effects. Examples illustrate advances in materials studies and models over the years in aero-engine and automotive applications.