• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.281-286
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• 2001

TiAIN was deposited onto ISO P2O Cutting Insert Tip substrate by FVAS at the substrate temperature of 80$^{\circ}C$. Cutting and wear test have been performed with TiAIN coated and uncoated WC cutting tools, respectively. Uncoated WC cutting tool has been tested under similar cutting condition for comparison. Cutting force and tool wear of coated and uncoated carbide cutting tools were investigated by cutting length. In cutting test, cutting force of the coated insert tip was larger than the uncoated insert tip by tool wear. Configuration and wear of the coated tool were more stable and resistant than the uncoated. In tool life by the tool wear, the coated cutting tool life was rather longer than the uncoated when tested at high speed (V=250 m/min) than low speed (V=200 m/min), Cutting force, tool wear and life were analysised by tool dynamometer amp(3ch) and oscilloscope.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.39-45
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• 2000

This paper describes the fundamental investigations on the in-process monitoring techniques focused on Acoustic Emission(AE) based on analytical method. Experiments were conducted on a CNC lathe using conventional carbide insert tools under various cutting conditions. As the result of this study a suggestion is given about the multi-purpose use of AE-signals detected with a single sensor for the monitoring of tool wear, built-up edge and chatter vibration in turning process.

• IE interfaces
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• v.7 no.3
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• pp.155-168
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• 1994

In computer integrated manufacturing environment, tool management plays an important role in controlling tool performance for machining operations. Knowledge of tool behavior during the cutting process and effective tool-behavior prediction contribute to controlling machine costs by avioding production delays and off-target parts due to tool failure. The purpose of this paper is to review and develop the tool condition monitoring scheme for drilling operation to assure a fast corrective response to minimize the damage if tool failures occur. If one desires to maximize system through-put and product quality as well as tooling resources, within an economic environment, real-time tool sensing system and information processing system can be coupled to provide the necessary information for the effective tool management. The example is demonstrated as to drilling operation when the aluminum composites are drilled with carbide-tipped HSS drill bits. The example above is limited to the situation that the tool failure mode of drill bits is wear.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1102-1103
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• 2006

The pretreatment for substrate was carried out in change of gun pressure of $0.5\sim3.5$ bar using wet blasting. The size of $Al_2O_3$ powder was about $50{\sim}150{\mu}m$. As the results, the surface roughness of cemented carbide substrate was improved with increment of gun pressure of wet blasting. A new surface layer was formed and Co particles were uniformly distributed over the entire surface after pretreatment. The adhesion of the pretreated substrate in same PVD-TiAlN film was improved and in approximately $Ra=90\sim120\;nm$ shown the best adhesion value.

• Journal of the Korean Society for Precision Engineering
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• v.8 no.1
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• pp.84-95
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• 1991

This paper deals with crater wear when the SUS304 steel which forms the saw- toothed chip was cut by carbide tools. When the saw-toothed chip was formed, and optical creater wear measuring technique was used which provides complete information, both qualitatively and quantitatively, on the crater development. In this optical contour mapping technique an profile projector was used, making it possible to draw the depth contours of the crater directly. 98 contour maps of crater wear representing twelve different cutting conditions were presented. Also, the rake angles changed to have ${\alpha}$ =$6^{\circ}$, ${\alpha}$ =$-6^{\circ}$

• Journal of Powder Materials
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• v.24 no.3
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• pp.202-209
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• 2017

A cold-work tool steel powder is used to fabricate 3-dimensional objects by selective laser melting using a high-pressure gas atomization process. The spherical powder particles form continuous carbide networks among the austenite matrix and its decomposition products. The carbides comprise Nb-rich MC and Mo-rich $M_2C$. In the SLM process, the process parameters such as the laser power (90 W), layer thickness ($25{\mu}m$), and hatch spacing ($80{\mu}m$) are kept fixed, while the scan speed is changed from 50 mm/s to 4000 mm/s. At a low scan speed of 50 mm/s, spherical cavities develop due to over melting, while they are substantially reduced on increasing the speed to 2000 mm/s. The carbide network spacing decreases with increasing speed. At an excessively high speed of 4000 mm/s, long and irregularly shaped cavities are developed due to incomplete melting. The influence of the scan pattern is examined, for which $1{\times}1 mm^2$ blocks constituting a processing layer are irradiated in a random sequence. This island-type pattern exhibits the same effect as that of a low scan speed. Post processing of an object using hot isostatic pressing leads to a great reduction in the porosity but causes coarsening of the microstructure.

• Journal of the Korean Society for Heat Treatment
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• v.28 no.5
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• pp.239-249
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• 2015

Various amount of NbC carbide was intentionally formed in a matrix-type cold-work tool steel by controlled amount of Nb and C addition. And the effect of NbC addition on the mechanical properties was investigated. Four alloys with different Nb and C contents were cast by vacuum induction melting, then hot forging and spheroidizing annealing were conducted. The machinability of the annealed specimens was examined with 3 different cutting tools. And tensile tests at room temperature were conducted. After quenching and tempering, hardness and impact toughness were measured, while wear resistance was evaluated by disk-on-plate type wear test. The increasing amount of NbC addition resulted in degraded machinability with increased strength, whereas the absence of NbC also led to poor machinability due to high toughness. After quenching and tempering, the additional NbC improved wear resistance with increasing hardness, whereas it deteriorated impact toughness. Therefore, it could be found that a moderate addition of NbC was desirable for the balanced combination of mechanical properties.

• Journal of the Korean Society for Heat Treatment
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• v.28 no.4
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• pp.181-189
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• 2015

Two types of advanced cold-work tool steels were characterized and compared. A higher-alloyed ledeburitic steel with primary carbides (denoted as 9Cr) and a lower-alloyed steel without primary carbides (5Cr) were fabricated by vacuum induction melting and subsequent hot forging. They were spheroidizing-annealed at $870^{\circ}C$, quenched at $1030^{\circ}C$ and tempered at 180 or $520^{\circ}C$. Their machinability after annealing and hardness, impact toughness, wear resistance after tempering were compared and interpreted in association with their characteristic microstructures. After annealing, 5Cr showed higher resistance to machining due to higher ductility and toughness in spite of lower strength and smaller carbide volume. Owing to smaller carbide volume fraction and the absence of coarse primary carbides, 5Cr showed even better impact toughness although the hardness was lower. The improved toughness of 5Cr resulted in excellent wear resistance, while smaller volume fraction of retained austenite also contributed to it.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.33-38
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• 1995

In this study, unsistered, pre-sintered and sintered low purity alumina ceramics were machined with various tools to clarify the machniability, the optimum tool materials and the optimum tool materials and the optimum cutting conditions. The maon conclusions obtained were as follows. (1) Machined withalloy steel tool, the machinabilty of te pre-sintered ceramics becomes better with the decrease of pre-sintering temperature, but that of unsintered ceramics(white body) was extremely poor. (2) In the case of carbide tool K01, the tool life in machining white body was the longest, and the machinabilty of pre-sintered ceramics becomes poorer with the increase of the pre-sintering temperature. (3) In the case of ceramic tool, the 10000-1100 .deg. C pre-sintered ceramics showed te best machinability within a certain cutting speed range. So far as dry machining, the above combination and conditions showed the highest productivity. (4) When the pre-sintered ceramics were wet machined withsintered diamond tool, the tool life becomes extremelylong, and higher cutting speed can be can be used than in the case offull-sintered ceramics. The productivity of wet cutting is much higher than that ofdry cutting.

• Journal of the Korean Society for Heat Treatment
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• v.31 no.6
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• pp.290-299
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• 2018

The microstructure of a newly developed alloy tool steel (KV1) for casting cold-work press dies was analyzed using advanced scanning electron microscopy. Its mechanical properties and durability in use as piercing inserts were tested. It contained a continuous network structure which originated from the micro-segregation during solidification and was composed of retained austenite and primary carbides. However, after quenching and tempering, its continuity was destroyed due to the decomposition of austenite. The discontinuous spatial distribution and the smaller amount of primary carbide in the network presented KV1 enhanced ductility compared to the common alloy (HK700). The reduced C and Cr, the addition of V resulted in a small amount of primary carbides which primarily consisted of MC, as well as fine and uniform dispersion of precipitates. Owing to these features, KV1 exhibited delayed initiation of chipping when used for piercing inserts.