In situ TiC/Inconel 625 nanocomposites fabricated by selective laser melting: Densification behavior, microstructure evolution, and wear properties

An Inconel 625-based nanocomposite reinforced with TiC nanoparticles (TiC/IN625) was successfully prepared by selective laser melting. The effects of laser fluence on the densification, microstructure, crystal structure, microhardness, and wear performance of the prepared nanocomposites were systematically investigated. A low laser fluence induced many defects, such as pores, cavities, and unmelted particles, whereas a high laser fluence resulted in a significantly increased densification. The increase in the laser fluence resulted in the continuous development of the microstructure of TiC/IN625 nanocomposites. A laser fluence of 139 J/mm(3) led to insufficient growth, while a sufficient growth was achieved at the laser fluence of 167 J/mm(3); at 208 J/mm(3), refined columnar/cellular dendrites were formed. Compared to IN625, smaller grains (less than 5 mu m) and a larger proportion of sub-grain boundaries appeared in the TiC/IN625 nanocomposites due to grain refinement. The TiC phases precipitated in situ in the grain boundaries, and a high level of dislocation was introduced into the TiC/IN625 nanocomposites. The maximum microhardness of the TiC/IN625 nanocomposites was 440 HV at the laser fluence of 208 J/mm(3). The lowest coefficient of friction and wear rate were 0.33 and 3.5 x 10(-4) mm(3) N-1 m(-1), respectively.