Anisotropic mechanical properties of ni-base superalloy compacts by direct laser forming technology

As Ni-based superalloy has poor workability, direct laser forming (DLF) would be a powerful tool for fabricating the complex shaped Ni-based superalloy parts. We focused on the microstructure of the parts produced by DLF, the crystal grains of which grow along the building direction. This anisotropic microstructure is one of the major features of the parts produced by DLF, and which may cause anisotropic mechanical properties. In this work, the optimum laser-forming conditions such as laser power, laser scan speed, and powder feeding rate were determined by evaluating the density of the produced parts. Three types of tensile test pieces and two types of fatigue test pieces were fabricated in different building direction. They had higher ultimate tensile strength than that of JIS standards in wrought materials. However, their elongation was lower than that of JIS standards, and also the dispersion of elongation was large. On the other hand, fatigue limit was a little lower than the standard value. It was confirmed that the mechanical properties of Ni-based superalloy parts produced by DLF were different by a difference in building direction.