Microstructure and fracture behavior of TiC particles reinforced Inconel 625 composites prepared by laser additive manufacturing

Laser additive manufacturing (LAM) is applied to manufacture particles reinforced composites due to its high designability, non-mold and high working flexibility. In this paper, TiC particles reinforced Inconel 625 composites were fabricated by LAM technology. Microstructure and chemical compositions of the composites were detected using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Meanwhile, macroscopic Brinell and micro Vickers hardness and in situ tensile test were applied to explore the hardness and fracture behavior of the composites. Results indicate that the microstructure of the composites consist of randomly distributed and partially melted TiC particle reinforcements, and in situ formed MC (M = Nb, Ti and Mo) precipitates with rod like shape appearing in interdendritic areas with a refined microstructure. A MC (M = Nb, Ti and Mo) transition region is observed at the interface between TiC/gamma matrix. The hardness of composites was 231 Brinell, 56% higher than that of the laser additive manufactured Inconel 625. However, high hardness and brittleness of reinforcements and precipitates cause unwanted cracks generation during deformation of the materials, and which will later propagate into the matrix and lead to final failure of the composites. The transition region at TiC/gamma matrix interface with coherent phase boundary enhanced the bonding strength thus no peeling of particles were observed during the fracture test. (C) 2017 Elsevier B.V. All rights reserved.