Effect of the building direction on the high-temperature mechanical properties of an IN738LC superalloy processed by laser-powder bed fusion

The building direction of a laser powder bed fused (L-PBF) material is critical since the existing temperature gradient is one of the main factors that influence the formation of the microstructure and thus, influences the mechanical properties of the material. In this contribution, the mechanical properties at high temperatures of a precipitation strengthened L-PBFed IN738LC nickel-based superalloy have been studied. The microstructure of the alloy has been characterized and statistically studied to synthesize representative volume elements (RVE) for performing crystal plasticity (CP) simulations. The results of this investigation evinced the effect of the building direction on the mechanical properties of the materials. Specimens loaded perpendicular to the building direction (BD) showed superior elastic properties. The plastic behavior of the alloy was found, however, not to be substantially affected by the BD. A CP-FEM model was modified to incorporate Kear-Wilsdorf (K-W) locks to model plastic deformation at elevated temperatures. The simulations substantiated that this mechanism influences significantly the material's deformation behavior in the moderate temperature range. At high temperature, the prediction was less accurate owing to a change in the operating mechanisms for plastic deformation, where degradation of the material was found to strongly influence the behavior. In turn, the degradation was associated to the oxidation along grain boundaries and intergranular crack propagation.