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.
기존에 개발된 TiC 입자강화 Fe 기지 금속복합재료는 TiC 분말과 Fe alloy 분말의 혼합 및 치밀화 공정을 이용하는 분말야금 공정을 통해 제조하고 있다. 하지만, TiC 입자와 Fe alloy 기지 간의 오염을 야기할 수 있으며, 강화입자 크기가 TiC 분말 초기 입자 크기에 제한되는 단점이 있어 강화효과를 극대화하지 못한다. 이에, TiC 강화상을 제조 공정 중에 인시츄 반응으로 형성하여 인시츄 TiC/Fe 금속복합소재를 제조하는 공정이 연구되었다. 기존 공정에 비해 TiC 강화상을 미세화 할 수 있으며, 계면 결합이 우수하다고 보고되었다. 하지만, 기존의 연구는 인시츄 반응으로 형성된TiC의 실제 화학당량을 고려하지 않았으며, 인시츄 TiC의 형성 가능성을 주로 연구하였을 뿐, 기존 공정으로 제조된 소재와의 비교 분석이 수행되지 않았다.
본 연구에서는 TiC와 Fe 기지 간의 계면특성이 우수하고 기계적 특성이 향상된 인시츄 TiC/Fe 금속복합재료의 제조공정을 개발하고 기존의 공정을 통해 제조된 소재와의 미세조직 및 기계적 물성 비교 분석을 수행하였으며, TiC 강화상과 Fe 기지 간의 계면 특성 및 강화 기구를 해석하였다.
