• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.898-901
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• 2000

It is known that Si3N4 ceramic insert has less hardness than Al2O3 ceramic insert. But Si3N4 ceramic insert has not only high toughness and strength but also low thermal expansion coefficient, which makes it has longer tool life under thermal stress condition. In this study, commercial Si3N4 ceramic insert and home-made SiC-Si3N4 ceramic insert which has different sintering time and chemical composition is tested under various cutting conditions. The experimental result is compared in terms of tool life and cutting force. Generally, As the cutting speed and the feed rate increased, the cutting force and the flank wear increased too. The performance of SiC-Si3N4 ceramic insert shows the possibility to be a new ceramic tool.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.12
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• pp.1944-1949
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• 2001

Four SiC-Si$_3$N$_4$ceramic cutting tools with different composition have been fabricated by hot-pressing. Correlations among the annealing time, the corresponding microstructure and the mechanical properties of resulting ceramics have been investigated. The fracture toughness and the grain size of both SiC and Si$_3$N$_4$in SiC-Si$_3$N$_4$composites increased with the annealing time. 1\`he hardness of SiC-Si$_3$N$_4$composites was relatively independent of the grain size and the sintered density. These ceramic cutting tools were tested under various cutting conditions and compared with the commercial Si$_3$N$_4$ceramic cutting tools. The experimental results were compared in terms of tool life and cutting force. The performance of SiC-Si$_3$N$_4$ceramic cutting tool shows the possibility to be a new ceramic tool.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.04a
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• pp.321-326
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• 2001

In the present study, $Si_3N_4-SiC$ ceramic composites that contained up to 20 wt% of dispersed SiC particles were fabricated via hot-pressing with an oxynitride glass. The microstructure, the mechanical properties, and the cutting performance of resulting ceramic composites were investigated. By fixing the composition as $Si_3N_4-20$ wt% SiC, the effect of sintering time on the microstructure, the mechanical properties, and the cutting performance were also investigated. For machining of gray cast i개n, the tool life increases with increasing the amount of SiC content in the composites; The tool life also increased with increasing the sintering time. The tool life of the home-made cutting tools was very close to that of commercial $Si_3N_4$ cutting tool. The superior cutting performance of $Si_3N_4-SiC$ ceramic cutting tools suggests the possibility to be a new ceramic tool material.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.386-391
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• 2000

It is known that Si$_3$N$_4$ceramic insert has less hardness than A1$_2$O$_3$ceramic insert. But Si$_3$N$_4$ceramic insert has not only high toughness and strength but also low thermal expansion coefficient, which makes it has longer tool life under thermal stress condition. In this study, commercial Si$_3$N$_4$ ceramic insert and home-made SiC-Si$_3$N$_4$ceramic insert which has different sintering time and chemical composition is tested under various cutting conditions. The experimental result is compared in terms of tool life and cutting force. Generally, As the cutting speed and the feed rate increased, the cutting force and the flank wear increased too. The performance of SiC-Si$_3$N$_4$ceramic insert shows the possibility to be a new ceramic tool.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.6
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• pp.78-84
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• 2001

In the present study, SiCSi-$Si_3 N_4$-SiC ceramic composites that contained up to 30 wt% of dispersed SiC particles were fabricat-ed cia hot-pressing with an oxynitride glass. The microstructure, the mechanical properties and the cutting performance of resulting ceramic composites were investigated. By fixing the composition as $Si_3 N_4$-20wf%SiC, the effect of sintering time on the microstructure, the mechanical properties and the cutting performance were also investigated. The longer sir-tering time is, the bigger the grain size of SiC is. The fracture toughness(-$K_k$) of the $Si_3 N_4$-SiC ceramic composites increased with the increase of gain size, while the flexural strengthh($\sigma$) decreased. For machining SCM440, the insert with 20wt%r SiC sintered for 8 hours showed the longest tool life while the insert with 20wt% SiC sintered for 12 hours showed the longest tool life for machining gray cast iron.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.655-659
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• 2002

This study is performed to develop the Si$_3$N$_4$ based ceramic inserts. Si$_3$N$_4$with addition of SiC and A1$_2$O$_3$ is investigated to determine the possibility to be a new tool. The tool life of Si$_3$N$_4$ insert with more than 20wt% SiC is shorter than commercial Si$_3$N$_4$ insert during machining both heat treated SCM440 and gray cast iron. Even though SiC has higher hardness than Si$_3$N$_4$, its chemical affinity to the iron on high temperature may causes deteriorat ion of tool life. To the contrary, Si$_3$N$_4$insert with A1$_2$O$_3$ shows increase of tool life up to 300% compared to the commercial Si$_3$N$_4$insert. It may attribute to the high temperature stability of A1$_2$O$_3$. Further study will be focused on the optimization of ceramic inserts with the composition of Si$_3$N$_4$and A1$_2$O$_3$.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.9
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• pp.89-95
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• 2001

Ceramic tool has to equip with not only high toughness and strength but also low thermal expansion and good thermal conductivity which leads to the high thermal shock resistance. These characteristics make it have longer tool life under thermal stress condition. In this study, commercial Si$_3$N$_4$ceramic cutting tool and home-made SiC based ceramic cutting tools which have different sintering time and chemical composition are tested under various cutting speed and the feed rate increase, the cutting force and the flank wear growth ratio increase, too. The performance of home-made SiC based ceramic cutting tool shows the possibility to be a new ceramic tool.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.4
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• pp.23-29
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• 2004

In this study, four kinds of $Si_3N_4$-based ceramic cutting tools with different sintering time were fabricated to investigate the relation among mechanical properties, grain size and tool life. They were used to turn gray cast iron at a cutting speed of 330m/min and depth of cut of 0.5mm and 1mm in dry, continuos cutting conditions. Multiple linear regression model was used to determine the relations among the mechanical property, grain size and the density. It was found that the combination of hardness and fracture toughness showed a good relation with tool life. It was also shown that hardness was the most important single element for the tool life.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.59-65
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• 2003

Four kinds of $Si_3N_4$-based ceramic cutting tools with different sintering time were fabricated to investigante the effect of sintering time on the microstructure, mechanical properties, grain sizes and the cutting performance. An endeavor was also made to determine the relation among mechanical property, Brain size and tool life. $Si_3N_4$ home made cutting tool sintered for 1 hour under $1760^{\circ}$ temperature and 25MPa pressure showed the best cutting performance among selected ceramic tools during machining both Bray cast iron and heat treated SCM440. Multiple linear regression model was used to estimate the tool lift from mechanical property, grain size and showed good result. It was also shown that hardness imposed the biggest offect on tool life.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.1
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• pp.111-116
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• 1998

Silicon nitride is hard and tough ceramic material. Hereby, mechanical machinability is very poor. It has also high electrical resistance. Silicon nitride of extremely high electrical resistivity becomes conductive ceramic composite by adding 30 wt% TiN. Ceramics with high electrical conductivity can be electrical discharge machined. Using by the Electrical Discharge Machining (EDM) technique. $Si_3N_4-TiN$ ceramic composite with high electrical conductivity is utilized to make metal working tool. These tool materials have severe wear problem as well as oxidation. Post HIP processing after sintering $Si_3N_4-TiN$ ceramic composites was performed. The tribological property of $Si_3N_4-TiN$ composite as a function of content of TiN was investigated in air, at room temperature. The hardness, fracture toughness, and flexural strength were compared with the wear volume. SEM observation of wear tracks can make an explanation of wear mode of $Si_3N_4-TiN$ composite.