Cyclic stress-strain behavior of additively manufactured gamma prime strengthened superalloy at elevated temperatures

The gamma-precipitation hardened nickel-based superalloy IN939 manufactured by laser powder bed fusion (L-PBF) was subjected to cyclic loading to determine the cyclic stress-strain curve by short-cut procedure. The effect of building on loading direction/orientation was investigated. (001) crystallographic texture along the building direction was observed. The cyclic stress-strain curves were measured at 800 degrees C and 900 degrees C and the differences in cyclic plasticity were revealed. The specimens prepared by L-PBF with a building direction parallel to the loading axis exhibited the highest cumulative plastic deformation at both temperatures, while L-PBF with a building direction perpendicular to the loading axis was the lowest. Elastic moduli were determined and the differences were attributed to the crystallographic texture. In addition, conventionally cast IN939 was investigated as the reference material. Minor microstructural changes due to cyclic straining were inspected by transmission electron microscopy.