Fabrication of ex-situ TiN reinforced IN718 composites using laser powder bed fusion (L-PBF): Experimental characterization and high-fidelity numerical simulations

In this study, IN718 metal matrix composites (MMCs), with TiN content of 0-30 vol %, have been fabricated using laser powder bed fusion (L-PBF). The process has been carried out with varying scanning speeds of 500-800 mm/s, while maintaining constant laser power (100 W), hatch overlap (- 50%) and layer thickness (25 & mu;m). A 2D numerical model has been established using the phase-field (PF) method to understand the role of driving forces (e.g., Marangoni force, thermal buoyancy force and recoil pressure) and deformation of melt pool behavior at different scanning speeds. In addition, the particle tracing model was coupled in the PF model to understand the motion of the reinforced particles. The microstructure of the fusion zone (or melt pool) has been predicted by evaluating the temperature gradient, solidification rate, and cooling rate. The solidification map of IN718 alloys indicated the microstructure of the fusion zone to be columnar dendrites at both the scanning speeds (500 mm/s and 800 mm/s). Depending upon the scanning speed, various defects (keyhole, balling and fusion defects) were observed in the fabricated composites. At 500 mm/s, the fabricated composite exhibited the lowest porosity (- 0.27 vol%). The mechanical properties of MMCs were evaluated in terms of micro-hardness and wear resistance. The micro-hardness of MMCs increased with an increase in the TiN content and decrease in the scanning speed. The wear resistance of IN718 MMCs was found to improve when the TiN content was increased (up to 20% vol. %).