Study On In-situ Synthesis Of TiC-TiB₂/Ni Composite By Induction Heating

Exothermic Dispersion is a kind of effective in-situ synthesis technology, which is also easy to control. In this paper Ti, Ni and B4C powders were used as raw materials and the milling time was 2h,8h and the volume fraction was 0%,5%,10%,15%,20% and 30%. TiC-TiB₂/Ni composites were prepared by electromagnetic induction heating. The reaction mechanism and the law of the kinetics about the growth of TiC and TiB₂ were discussed from the aspects of thermodynamics and kinetics by using DSC, XRD and SEM and so on. The compressive strength and antioxygenic property of the materials were tested and the mechanism of the material was analyzed by SEM.The study of the reaction mechanism showed that TiC and TiB₂ in the Ni-Ti-B4C system under the condition of DSC was revealed:TiC and TiB₂ were formed by dissolution reaction precipitation mechanism. The Ni-B and Ni-Ti liquid phase formed first and then mixed and formed to Ni-Ti-B-C liquid phase. In the end, the B, C and Ti atoms in the liquid phase precipitate TiC and TiB₂. The reaction activation energy increased with the increase of the volume fraction from 10% to 30%, and the activation energy decreased with the increase of the volume fraction. The reaction activation energy, whose milling time was 2h and volume fraction was 20% and 30%, was respectively 113.59kJ/mol and 182.34kJ/mol. When the milling time was 8h, the reaction activation was respectively 63.99kJ/mol and 100.01kJ/mol.Researches on the performance test show that Reinforcement volume fraction increased and the yield strength of the material increased. The compressive strength is the maximum when the volume fraction of reinforcement is 10%, which is 920MPa. Fracture mode of material gradually transformed from ductile fracture into quasi cleavage fracture.Oxidation resistance research show that:Oxidation activation energy of the pure nickel and volume fraction of 5%、10%、15%、20% of TiC-TiB₂/Ni composite are 6.5kJ/mol、15.24 kJ/mol、37.21 kJ/mol、39.24 kJ/molå’Œ 44.96 kJ/mol. With the increase of the volume fraction, the antioxidant properties of materials also increases. There are two oxide film formation, one is the oxide film first formed on the surface of nickel substrate. The other is formed by two layers, interactive stacking acicular oxide layer and spherical oxide layer, which is coated by nickel oxide.