Fabrication processes and properties of In-situ and Ex-situ TiC particles reinforced Fe matrix composites

Abstract

Titanium carbide (TiC) is an attractive reinforcement system for metal matrix composites because of its high melting temperature, excellent hardness, modulus and thermodynamic stability. On the other hand, Fe alloys with low price have great strength, toughness and high machinability. Thus, TiC reinforced Fe alloy matrix composites have been applied as various areas requiring high strength and wear resistance. However, TiC/Fe alloy composites by addition of TiC particles in Fe alloy matrix could have poor interfacial properties between the reinforcement and matrix due to contamination by impurities during fabrication processes. In this research, powder metallurgical process with the in-situ reaction has been developed to fabricate the in-situ TiC/Fe alloy composites. The reactant ratios to form the in-situ TiC particles in Fe alloy matrix are designed to optimize the in-situ reactive sintering process. Also, the mechanical properties of the in-situ TiC/Fe alloy composites has been compared with those of the ex-situ TiC/Fe alloy fabricated by addition of TiC particles. In addition, interfacial properties of the in-situ TiC and ex-situ TiC/Fe alloy composites are characterized. In comparison with mechanical properties with the ex-situ TiC/Fe alloy composites, the in-situ TiC/Fe alloy composites showed enhanced hardness and strength. Also, impact resistance of the in-situ TiC/Fe alloy composites was improved to 122% compared than that of the ex-situ TiC/Fe alloy composites. The improvement of impact resistance is attributed to different interfacial bonding between TiC phase and Fe alloy matrix. In addition, the in-situ TiC/Fe alloy composite exhibited increased wear resistance by 2 times higher than that of the ex-situ TiC/Fe alloy composite. The major wear mechanisms were demonstrated as debonding of TiC particles at worn surface which could be reduced in the in-situ TiC/Fe alloy composites due to improved coherency and interfacial bond strength between TiC phase and Fe alloy matrix.