Effect of TiC and TiB2 Reinforcement Phase Addition on Mechanical and Tribological Properties of NiAl-TiC-TiB2 Composite Produced Through Combustion Synthesis Process

In this research, NiAl-TiC-TiB2 composites with different contents of TiC-TiB2 were produced via the self-propagating high-temperature synthesis (SHS) process using the exothermic reactions in compressed mixtures of Ni, Al, Ti, and B4C. The synthesis of composites was performed using induction assisted heating, and the formation of phases and the morphology of reinforcing particles were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques, respectively. Results indicate that the TiC-TiB2 ceramic phases were successfully synthesized and dispersed throughout a NiAl matrix. By increasing the TiC-TiB2 content, the porosity in the structure gets a rising trend due to the enhancement of reaction kinetics and intensity of the reaction, and reaches from 24 Vol.% in the sample without reinforcement phases to 39% in the sample with 15% of ceramic reinforcements. Evaluation of mechanical and tribological properties of the fabricated ceramic samples shows that - although the addition of TiC-TiB2 increases the volume fraction of voids which cause destructive effects - a desirable distribution of ceramic particles within the NiAl matrix leads to improved properties for the composite. The distribution of TiC-TiB2 particles throughout the matrix results in a remarkable decrease in sample weight loss in the pin-on-disk wear test. Also, the microhardness mean values increase from 497 HV for the unreinforced NiAl sample to values up to 1015 HV for the composite sample containing 15% of reinforcing particles.