Abstract
The effect of hot isostatic pressing (HIP) treatment on high-temperature low cycle fatigue (LCF) behaviour of γ❜ precipitation strengthened nickel-based superalloy MAR-M247 was studied. Microstructural observations revealed coarse-grained dendritic structure with an average grain size of 2.1 mm. Distribution and size of casting defects were assessed on cross sections of both HIP treated and untreated MAR-M247. Shape and size of precipitates are documented. Vickers hardness tests did not reveal differences between both materials. Untreated specimens were cyclically strained under total strain control at 900 °C. Likewise, tests were performed on the HIP treated material at temperatures of 900 and 950 °C. The stress-strain response was recorded. Coffin-Manson and Basquin fatigue life curves were established. HIP treatment leads to an increase of lifetime in comparison with the untreated material. Precipitate depleted zone was observed and crack initiation sites were identified. Dislocation arrangements were studied in TEM. Planar bands containing antiphase boundaries are observed.

Key words
hot isostatic pressing, Ni-based superalloy, high-temperature low cycle fatigue, fatigue life curves, dislocation structures, planar bands

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