Creep deformation and fracture of superalloy IN939 produced by L-PBF method

Inconel 939 is a high-temperature nickel superalloy exhibiting an excellent combination of fatigue and creep properties with high oxidation and corrosion resistance. Therefore, it is often used for high-temperature applications, mainly in cast form. Laser powder bed fusion (L-PBF) technology has become a promising manufacturing method for producing power components with complex geometries that would be difficult to manufacture with other conventional technologies. However, the microstructure of the printed superalloy is completely different from the conventional as-cast state due to the high-temperature gradients and solidification rate during the L-PBF process. The article is focused on the creep behaviour and fracture mechanisms of the nickel superalloy IN939 produced by the L-PBF method at three temperatures 700, 800, and 900°C, in the wide range of applied uniaxial tensile stresses. The creep results show that the creep deformation of the INC939 alloy prepared by the L-PBF method is in the region of power-law dislocation creep. The values of the determined stress exponents of the minimum creep rate and time to fracture indicate that the controlling creep deformation mechanism and the fracture mechanism are identical. The power-law creep regime is explained by a dislocation climb-controlled mechanism. Creep strain, however, arises mainly through the glide of mobile dislocations.