Creep properties and deformation mechanisms of single-crystalline <i>γ</i>′-strengthened superalloys in dependence of the Co/Ni ratio

Co-base superalloys are considered as promising high temperature materials besides the well-established Ni-base superalloys. However, Ni appears to be an indispensable alloying element also in To address influence of base elements on deformation behaviour, high-temperature compressive creep experiments were performed a single crystal alloy series that was designed exhibit varying Co/Ni ratio and constant Al, W Cr content. Creep tests at 900 °C 250 MPa resulting microstructures defect configurations characterised via electron microscopy. The minimum rates differ by more than one order magnitude with changing ratio. An intermediate CoNi-base exhibits overall highest strength. Several strengthening contributions like solid solution γ phase, effective diffusion coefficients or stacking fault energies quantified. Precipitate shearing mechanisms significantly when content is varied. While Ni-rich SISF SESF shearing, Co-rich alloys develop extended APBs γ′ phase cut. This mainly attributed difference planar energies, caused segregation behaviour. As result, it assumed resistivity occurring crucial for properties investigated series.