Enhanced mechanical properties and microstructure of TiC reinforced Stellite 6 metal matrix composites (MMCs) via laser cladding additive manufacturing

In the present study, Stellite 6 (Co-Cr-W-C group of superalloy) and Stellite 6-TiC MMCs have been successfully fabricated by process optimization via laser cladding additive manufacturing. Addition of TiC particles resulted in significant grain refinement of the matrix and generation of strains in the vicinity of the particle-matrix interface, which contributed to the indirect strengthening of the composite. Moreover, the columnar to equiaxed transition (CET) of the Stellite 6 grains was also noticed as TiC particles provided numerous heterogeneous nucleation sites ahead of advancing columnar grains of Stellite 6, which were confirmed by utilizing scanning electron microscopy (SEM) and electron back-scattered diffraction (EBSD) techniques. Transmission electron microscopy (TEM) study revealed the formation of secondary carbides of Ti, Cr, and W at the TiC particle-matrix interface, resulting in strong interfacial bonding. Incorporation of 10 vol%, 20 vol% and 30 vol% TiC particles enhanced the hardness of the composites by ∼ 26.7 %, ∼ 33.3 %, and ∼ 44.2 %, respectively. This was further corroborated with improvement in the wear resistance of composites. Stellite 6 with 10 vol% TiC composite exhibited superior sliding wear performance compared to 20 vol% and 30 vol% composites at room temperature. The shift of two-body abrasive wear in 10 vol% TiC composites to three-body abrasive wear in 20 vol% and 30 vol% composites was observed.