Additive manufacturing of complex-shaped graded TiC/steel composites

Complex-shaped TiC_x ceramic preforms with a gradient of carbon content in the titanium carbide phase (x changes from 0.7 to 0.98) were fabricated for the first time by Binder jet 3D printing technology. The complex-shaped preforms were infiltrated with molten carbon steel (0.7 wt.% C). Thermodynamic considerations showed that carbon could be transferred from titanium carbide to steel and vice versa according to the initial concentration of carbon (activity) in both phases. After infiltration, solidification and slow cooling, a microstructural gradient was obtained throughout the steel matrix from ferrite, in the region where the steel was in contact with titanium carbide of low carbon content (x = 0.7), to pearlite, in the region where the steel underwent interactions with stoichiometric titanium carbide (x = 0.98). After annealing at 900 °C and quenching in oil, a structural gradient in the steel matrix from ferrite to martensite was obtained, resulting in a hardness gradient of 700–1600 HV. The suggested processing approach allows for fabrication of complex-shaped graded composites with the desired property gradient suitable for a wide range of practical applications.