Influence of casting surface on creep behaviour of thin-wall Ni-base superalloy Inconel100

The conventionally cast nickel-base superalloy Inconel100 was investigated with the focus on the influence of the surface condition and the thin-section size on the creep properties. Flat samples with 0.9 mm and 1.3 mm thickness were wire eroded from precision cast ingots. Thin cast specimens with a remaining casting surface were compared with machined specimens which flat surfaces were subsequently ground to the final thicknesses. Microstructures were examined by optical and scanning electron microscopy. Creep tests in air at 980 °C under a constant load of 150 MPa revealed decreasing creep strength with decreasing sample thickness. However, thin cast samples and samples with a machined surface having the same thickness showed similar creep properties.