Papers by Author: In Shup Ahn

Abstract: In this study, the FeS2 fine compound powders for active material were made by mechanical alloying using the Spex mixer mill. As the total milling time increased to 15hrs, the size of FeS2 powder decreased to 0.98um. Meanwhile, the treatment of nickel coating for FeS2 powder were also prepared by mechanical alloying using the ball milling machine, which has attracted much attention from the standpoints of improving the cycle life property and good columbic efficiency.

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: Metal sulfide (MeS) is well known and widely used an additive for enhancing machinability, but the problems is extremely sensitive to reaction with moisture and thermal decomposition during sintering. In this study, micron or nano size compound powders of FeS were produced by mechano-chemical process. The machinability was also evaluated at the metal sulfide added sintered steel. Compared with the MnS additive, addition of the FeS powders to the iron resulted the formation of the sintering materials containing a spherical shape of pore, partly remained FeS rich-phase in iron matrix. Relative machinability behavior of sintering materials was investigated by the lathe manufacturing. Mechanical properties of sintering material with 1.2%FeS powders were improved rather than its using MnS powders.