Spark plasma sintering of WC-Co tool materials prepared with emphasis on WC core-Co shell structure development

Lee, S.,Hong, H.S.,Kim, H.S.,Hong, S.J.,Yoon, J.H. MPR Pub. Services 2015 INTERNATIONAL JOURNAL OF REFRACTORY METALS AND HAR Vol.53 No.1

Quasi-nano-sized WC core-Co shell structure composites were successfully fabricated by the wet chemical reduction method by introducing uniformly dispersed WC powders of 300-nm size into the Co(OH)<SUB>2</SUB>, which was subsequently reduced to Co shell structure by drop-wise titration of H<SUB>3</SUB>PO<SUB>2</SUB>. X-ray diffractometer (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) identified WC core-Co shell phases which were subsequently ball-milled, compacted and finally densified at 1400-1450<SUP>o</SUP>C by spark plasma sintering. WC-Co sintered composites thus prepared were analyzed to examine densification, hardness and fracture behavior: reasonably adequate post-sintering properties are attributable to improved WC core-Co shell structure afforded by the optimized mechanical alloying and SPS sintering processes.

다이아몬드공구에 의한 초경합금의 절삭

김성청,이재우 한국공작기계학회 1997 한국생산제조학회지 Vol.6 No.2

This paper deals with the machinability based on turning of WC-Co alloys with the coated and the sintered diamond tools. The main conclusions obtained are as follows. (1) When machining WC-10%Co alloy, the flank wear of sintered diamond tool increases more largely with the increase of cutting speed in comparison with coated diamond tool. The tool wear decreases with the increase of the grain size and nose radius of sintered diamond tool. (2) When machining WC-20%Co alloy, the tool wear and cutting force decrease with the decrease of rake angle. Their exists a certain cutting speed range to exhibit the smallest tool wear in machining the WC-20%Co alloy, and this critical cutting speed becomes higher by 2 times in the case of coated diamond tool compared with sintered diamond tool. (3) The machinability becomes better with the increase of Co content. The effects of cutting speed and feed rate on the roughness of machined surface become smaller with the increase of Co content.

WC-10Co4Cr으로 초고속 화염용사 코팅된 Cu 합금의 해수내 캐비테이션 손상 거동

한민수(Min-Su Han),김민성(Min-Sung Kim),장석기(Seok-Ki Jang),김성종(Seong-Jong Kim) 한국표면공학회 2012 한국표면공학회지 Vol.45 No.6

Due to the good corrosion resistance and machinability, copper alloy is commonly employed for shipbuilding, hydroelectric power and tidal power industries. The Cu alloy, however, has poor durability, and the seawater application at fast flow condition becomes vulnerable to cavitation damage leading to economic loss and risking safety. The HVOF(High Velocity Oxygen Fuel) thermal spray coating with WC-10Co4Cr were therefore introduced as a replacement for chromium or ceramic to minimize the cavitation damage and secure durablility under high-velocity and high-pressure fluid flow. Cavitation test was conducted in seawater at 15℃ and 25℃ with an amplitude of 30 μm on HVOF WC-10Co4Cr coatings produced by thermal spray. The cavitation at 15℃ and 25℃ exposed the substrate in 12.5 hours and in 10 hours, respectively. Starting from 5 hours of cavitation, the coating layer continued to show damage by higher than 160% over time when the temperature of seawater was elevated from 15℃ to 25℃. Under cavitation environment, although WC-10Co4Cr has good wear resistance and durability, increase in temperature may accelerate the damage rate of the coating layer mainly due to cavitation damage.

초소형 금형소재의 기계적 특성평가

강재훈,이현용,이낙규 한국공작기계학회 2005 한국공작기계학회 춘계학술대회논문집 Vol.2005 No.-

Today's manufacturing industry is facing challenges from advanced difficult-to-machine materials (WC-Co alloys, ceramics, and composites), stringent design requirements (high precision, complex shapes, and high surface quality), and machining costs. Advanced materials play an increasingly important role in modem manufacturing industries, especially, in aircraft, automobile, tool, die and mold making industries. The greatly-improved thermal, chemical, and mechanical properties of the material (such as improved strength, heat resistance, wear resistance, and corrosion resistance), while having yielded enormous economic benefits to manufacturing industries through improved product performance and product design, are making traditional machining processes unable to machine them or unable to machine them economically. In this paper, mechanical characteristic evaluation test of fine powder type WC-Co alloy was accomplished to obtain clear data for miniaturized special die parts machining with high reliability and high quality.

초소형 금형소재의 기계적 특성평가

강재훈(Jae-hoon KANG),이현용(Hyun-yong LEE),이낙규(Nak-kyu LEE) 한국생산제조학회 2005 한국생산제조시스템학회 학술발표대회 논문집 Vol.2005 No.5

Today's manufacturing industry is facing challenges from advanced difficult-to-machine materials (WC-Co alloys, ceramics, and composites), stringent design requirements (high precision, complex shapes, and high surface quality), and machining costs. Advanced materials play an increasingly important role in modem manufacturing industries, especially, in aircraft, automobile, tool, die and mold making industries. The greatly-improved thermal, chemical, and mechanical properties of the material (such as improved strength, heat resistance, wear resistance, and corrosion resistance), while having yielded enormous economic benefits to manufacturing industries through improved product performance and product design, are making traditional machining processes unable to machine them or unable to machine them economically. In this paper, mechanical characteristic evaluation test of fine powder type WC-Co alloy was accomplished to obtain clear data for miniaturized special die parts machining with high reliability and high quality.

Fabrication of WC-Co Cutting Tool by Powder Injection Molding

Dongguo Lin,Jifu Xu,Zhongde Shan,정석택,박성진 한국정밀공학회 2015 International Journal of Precision Engineering and Vol.16 No.7

In this work, a cutting tool for sand-mold milling was fabricated by powder injection molding (PIM) technology using 90WC-10Co alloy powder for machining sand molds in patternless sand-casting technology. The work included design of cutting tool tip, injection mold and binder system. Also, for the PIM process, mixing, injection molding, debinding and sintering process were investigated experimentally. Finally, the properties for final products were tested, such as micro structures, element composition, wear resistance and so on. The cutting tool fabricated by PIM had a final density of 14.21 g/cm3 (95% of theoretical density) and a dimension accuracy over 98%. Also, in sand-mold machining test, it showed an abrasion loss of 0.16 mm after working for 3 hrs. The results showed that a whole cutting tool was fabricated using PIM technology successfully, and it showed out good mechanical performances.

Growth Inhibition of Nano WC particles in WC-Co Alloys during Liquid-Phase Sintering

강신후 The Japan Inst. of Metals 2003 Materials Transactions Vol.44 No.11

미소박판금형의 고품위 연삭가공

강재훈(Jae-Hoon Kang) 한국생산제조학회 2007 한국생산제조시스템학회 학술발표대회 논문집 Vol.2007 No.5

The establishment of a practical ultra-precision grinding technique using diamond wheels is one of the major key technology to improve production techniques for machine-to-difficult materials such as WC-Co alloy without additional finishing process. But the special efficient dressing technique for ultra-fine grit type grinding wheels to obtain high quality machined surface with the stabilization of the grinding ability was not developed. Recently, electrolytic in-process dressing technique is proposed to ultra-fine grit type metal bonded diamond wheels to protrude abrasives continuously from the tool surface. In this study, various grinding experiments using such advanced dressing method were carried out to obtain high quality ground surface of fine sheet metal forming die. Then, in conclusion, ultra-precision ground die part with burr -free state can be manufactured differently in conventional grinding.

미소박판금형의 고품위 연삭가공

강재훈(Jae-Hoon Kang) 한국생산제조학회 2007 한국공작기계학회 춘계학술대회논문집 Vol.2007 No.-

The establishment of a practical ultra-precision grinding technique using diamond wheels is one of the major key technology to improve production techniques for machine-to-difficult materials such as WC-Co alloy without additional finishing process. But the special efficient dressing technique for ultra-fine grit type grinding wheels to obtain high quality machined surface with the stabilization of the grinding ability was not developed. Recently, electrolytic in-process dressing technique is proposed to ultra-fine grit type metal bonded diamond wheels to protrude abrasives continuously from the tool surface. In this study, various grinding experiments using such advanced dressing method were carried out to obtain high quality ground surface of fine sheet metal forming die. Then, in conclusion, ultra-precision ground die part with burr -free state can be manufactured differently in conventional grinding.

분무 건조된 W-Co 복합염의 열분해 및 분말 특성에 관한 연구

권대환,안인섭,하국현,김병기,김유영,Gwon, Dae-Hwan,An, In-Seop,Ha, Guk-Hyeon,Kim, Byeong-Gi,Kim, Yu-Yeong 한국재료학회 2001 한국재료학회지 Vol.11 No.11

Homogeneous spherical W-Co salt powders were made by spray drying of aqueous solution of ammonium $metatungstate(NH_4)_6(H_2W_{12}O_{40}){\cdot}4H_2O,\; AMT)$ and cobalt nitrate $hexahydrate(Co(NO_3)_2{\cdot}6H_2O)$. The thermal decomposition process of spray dried W-Co salt powders was studied by TG, XRD, SEM, TEM and FT-IR. Spray dried W-Co salt powders were calcined for 1 hour in the temperature from$ 350^{\circ}C$ to $800^{\circ}C$ in atmosphere of air. At the temperatures over $600^{\circ}C$, spherical $CoWO_4/WO_3$ composite oxide powders were obtained. The primary particle size of W/Co composite oxide powders increased with increasing thermal decomposition temperature due to the particle growth. The observed crystallite size by TEM was in the range of 60nm and that of $CoWO_4$ calculated by Scherrer's formula at $800^{\circ}C$ was smaller than 55nm. The crystallite site was identified by XRD and TEM.