Creep-fatigue-oxidation interactions in a 9Cr-1Mo martensitic steel. Part II: Effect of compressive holding period on fatigue lifetime

摘要

Cyclic tests with compressive holding periods were carried out in air at 823 K on a modified 9Cr-1Mo martensitic steel. In accordance with other results published in the literature, compressive holding periods were found more deleterious than tensile ones, i.e. fatigue lifetimes were more severely reduced under compressive holding periods than under tensile holds. For all tested samples a strong influence of oxidation was observed, and a tensile mean stress was measured due to compressive holding periods. To understand the difference between compressive and tensile holding periods, a detailed study of the oxide layers mechanical behavior was carried out. Based on an extensive literature survey, focussed on the fracture behavior of oxide layers, and on Finite Element (FE) calculations, a general scheme for modelling creep-fatigue-oxidation interactions is proposed and discussed.