Nanocrystalline TiC reinforced Ti matrix bulk-form nanocomposites by Selective Laser Melting (SLM): Densification, growth mechanism and wear behavior

Selective Laser Melting (SLM) Additive Manufacturing (AM) process was used to produce nanocrystalline TiC reinforced Ti matrix bulk-form nanocomposites. The influence of “volumetric energy density” (ε) on densification activity, microstructural feature, nanohardness, and wear behavior of SLM-processed parts was studied. The densification levels of TiC/Ti parts remained above 97% as ε ⩾ 120 J/mm3. A further decrease in ε lowered the densification rate, due to the occurrence of balling effect. The TiC reinforcement experienced an interesting morphological change from the coarsened dendritic TiC (360 J/mm3) to the accumulated whisker-structured TiC (180 J/mm3) and to the uniformly dispersed nanoscale lamellar TiC (⩽120 J/mm3). As ε of 120 J/mm3 was properly settled, the dynamic nanohardness (90.9 GPa) and elastic modulus (256 GPa) of SLM-processed TiC/Ti nanocomposites showed respectively ∼22.7-fold and ∼2.4-fold increase upon that of the unreinforced Ti. A uniform distribution of friction coefficient with a low average value <0.2 was obtained, leading to a considerably reduced wear rate of 1.8 × 10−7 mm3/(Nm). A disappearance of nanostructured TiC reinforcement at an elevated ε of 360 J/mm3 lowered the mechanical properties of TiC/Ti part consisting of the coarsened dendritic TiC.