Papers by Author: Ho Jung Cho

Abstract: TiC-based cermets attract much attention because of their excellent wear-resistance, high hardness at high temperature, good chemical stability, superior thermal deformation resistance. Therefore, titanium carbide is mainly used for cutting tools, grinding wheels, coated cutting tips and coated steel tools. In this research, Fe-TiC composite materials were fabricated by spark plasma sintering (SPS) after mechanical alloying. TiH2 and graphite powders were used to synthesize TiC phase. In order to compare the properties of sintered materials using mixture powder (D’AE+TiH2+graphite), commercial TiC powder was mixed with Distaloy AE (D’AE) powder as a same mechanical alloying method. Then, the shape of each mixture powder (D’AE+TiH2+graphite, D’AE+TiC (commercial)) and sintering properties were compared. TiC phase was synthesized by self-propagating high-temperature synthesis (SHS) reaction during spark plasma sintering. It was confirmed by using X-ray diffraction (XRD). Energy dispersive spectrometry (EDS) and Scanning electron microscopy (SEM) were used to observe shape of mixture powders and also sintering properties were examined such as hardness, relative density. In case of sintered material for 10min holding time at 1373K after mechanical alloying for 1 hour with D’AE, TiH2 and graphite, it indicated higher hardness value 49HR-C than a case using D’AE and TiC powder.

Abstract: TiC cermet is widely used for working dies with a high hardness and tool materials. In this research, we attempted to produce submicron sized TiC powders from the ball milled TiH2 and carbon black mixture by thermal treatment. The titanium hydride and carbon composite powders were milled under argon atmosphere for 7 hours at various ball to powder ratios. At the initial stage, an increase in particle size was observed, and graphite phase disappered. The TiC phase of 300nm mean particle size was obtained by milling for 5 hours. As a result, its morphologies were excessively agglomerated. At the heat treating temperature of 500°C, TiH2 phase transformed to Ti completely and the complete TiC of lattice parameter 0.431 nm was formed when the temperature reached 1000°C. Metal matrix composites(MMCs) based on the Fe-TiC system can be synthesized by spark plasma sintering. Specimen formed sintering Fe-TiC powders display a microstructure of uniformly dispersed TiC grain in a continuous metal matrix.

Abstract: TiC particulate reinforced Fe matrix composite compacts with controlled interfacial reaction was processed by spark plasma sintering after mechanical alloying. Milled powders were fabricated for 1-5 hours by spex shaker mill with the ball to powder ratio of 25:2. Metal matrix composites (MMCs) based on the Fe-40%TiC system can be synthesized by spark plasma sintering of the D’AE powders with TiH2-graphite powders under vacuum in the temperature range 1273-1473K for 5-20 min. TiC phase was formed by self combustion reaction with temperature increase. The specimen that was formed by sintering Fe-TiC powders displayed a microstructure of uniformly dispersed TiC grain in a continuous metal matrix. The densifications of the TiC-Fe materials were increased as the heat-treatment holding time increasing. In the same time, relative density and hardness of TiC-Fe sintering materials was increased.