Effects of Ni content and sintering temperature on the microstructure and mechanical properties of TiC-Ni composites fabricated by selective carburization of Ti-Ni alloys

The effects of Ni content and sintering temperature on the microstructure and mechanical properties of TiC-Ni composites prepared by selective carburization of Ti-Ni alloys were investigated. It was found that coherent boundaries between TiC and Ni were formed after sintering because Ni was attached to TiC in the powdered form. Grain growth by dissolution and precipitation of TiC in Ni was limited during sintering at 1400 °C (below melting point of Ni). As a result, the grain size of TiC did not change with increase in the amount of Ni. However, the grain size of TiC increased with an increase in Ni content at 1500 °C (above melting point of Ni) because the dissolution and precipitation of TiC was promoted in the melted Ni. The fracture toughness (∼18 MPa m^1/2) of TiC-Ni composite fabricated at 1500 °C in this study was higher than that (∼11 MPa m^1/2) of TiC-Ni composite in the previous study (sintered at 1330 °C) because of effect of the enlarged grains. The hardness was also enhanced by decreasing the content of Ni (13 GPa → 13.5 GPa). Consequentially, it was found that the microstructure and mechanical properties of TiC-Ni composites were customized by controlling the Ni content and sintering temperature in the process suggested in this study.