Heat Treatment of IN 718 Produced by Laser Powder Bed Fusion Process: Effect of Thickness on the Microstructural Characteristics

Laser powder bed fusion (L-PBF) is an additive manufacturing technique through which components are built by selectively melting powder layers with a focused laser beam. The as-built microstructures have a great impact on the phase transformation and precipitation behavior during subsequent heat treatment.

This study was directed to understand the effect of component thickness, in the case of complex shape components, on the microstructure, type of precipitates of L-PBF IN 718 in as-built and heat treated conditions. Standard heat treatment cycles per ASTM F3055 and AMS 2774D were investigated.

This work shows that microstructure, grain size, types of precipitates, and formed phases of components produced by L-PBF in the as-built condition and after heat treatment are profoundly different with different components thicknesses. In order to obtain optimal microstructure and mechanical properties, specific heat treatments are necessary due to the complexity of the components produced.