Browsing by Author "KUO, CT"

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A NEW SIMPLE CASTING TECHNIQUE - THE FLYING WHEEL CASTING
(1983)
ABDELREIHIM, M
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KUO, CT
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REIF, W
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交大名義發表
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National Chiao Tung University
ADHESION AND TRIBOLOGICAL PROPERTIES OF DIAMOND FILMS ON VARIOUS SUBSTRATES
(1990-11-01)
KUO, CT
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YEN, TY
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HUANG, TH
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HSU, SE
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機械工程學系
ALUMINA-CHROMIUM CARBIDE COMPOSITE THROUGH AN INTERNAL SYNTHESIS METHODS
(1992-11-01)
CHUANG, SC
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KUO, CT
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LEE, CS
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HO, CT
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LI, AK
In situ formation of chromium carbide parlicles, through a solid state reaction between Cr2O3 and SiC, for strengthening Al2O3 has been studied. Three kinds of chromium compound, Cr3Si, Cr3C2 and Cr7C3 and mullite were formed in the alumina matrix. The reaction behaviour during hot pressing depends on heating parameters such as temperature and atmosphere. In a vacuum environment, the Cr3Si particles formed first and was the dominant dispersed phase below 1550-degrees-C, while the Cr7C3 phase was only dominant above 1600-degrees-C. The Cr3C2 phase emerged briefly then diminished at temperature greater-than-or-equal-to 1500-degrees-C. In an argon environment, however, the Cr3C2 phase was the main product component at temperatures ranging from 1450-1550-degrees-C. The mullite phase formed concurrently through the diffusion Of SiO2 phase into the A12O3 matrix, which is a by-product from the reaction between Cr2O3 and SiC. Incorporating chromium carbide or silicide particles into the Al2O3 matrix induces a strengthening effect. However, only when the content of dispersed phases is low and is mainly of Cr3C2 particles, is the strengthening effect significant. For instance, the composite, containing 5 vol % chromium carbide and hot-pressed at 1500-degrees-C in argon, gives a flexural strength and fracture toughness up to 600 M Pa and 6.1 MPa m1/2, respectively.
DIAMOND FILM GROWTH ON CEMENTED TUNGSTEN CARBIDES STUDIED BY SEM, AES AND XPS
(1992-11-23)
CHEN, JL
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HUANG, TH
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PAN, FM
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KUO, CT
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CHANG, CS
Diamond films were deposited on cemented WC substrates using a hot filament chemical vapor deposition (CVD) system with a mixture of CH4 and H-2 as the source gases. The effect of the surface pretreatments of scratching the surface and etching to remove the surface Co from the substrate on diamond nucleation and growth was studied. The effect of CH4 Concentration on diamond growth was also examined. Scanning electron microscopy, Auger electron, X-ray photoelectron and energy dispersive spectroscopies were used to examine the film morphology, quality and compositions. The results show that a good diamond-crystal quality can be obtained by reducing the surface Co content in the substrate to below 1%. Co in the surface layer of the substrate inhibits both diamond nucleation and growth. Polishing and etching treatments to scratch the surface and to remove the surface Co of the substrates are essential to maintain the surface roughness in an appropriate range to obtain diamond films with a good quality and adhesion. A change in CH4 Concentration in the source gases from 0.5 to 0.15% can change the preferred orientation of the diamond films fro m the {100} to the {111} plane.
EFFECT OF ARC PLASMA-HEATING ON THE AIR POCKET FORMATION DURING THE PLANAR FLOW CASTING
(1991)
WANG, WK
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KUO, CT
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CHIN, TS
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機械工程學系
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Department of Mechanical Engineering
Air pockets have long been an unsatisfactory feature of the planar flow casting (PFC) process, which is a potential method for manufacturing thin strip. In this study, heating the gas on the wheel surface upstream of the puddle by means of an arc plasma was used to improve the puddle stability and inhibit air pocket formation. It was found that in the plasma heating region air pockets were almost invisible microscopically and the polishing tracks on the wheel surface were well-duplicated on the wheel side contact surface of the cast ribbon, while in the unheated regions a conventional air pocket characteristic was observed. This fact confirms that the thermal expansion of the gas in the converging contact angle, which builds up a local high pressure region at the melt/substrate interface, lifts up the melt and enhances the gas entrapment. Arc plasma heating reduces the temperature difference, hence the pressure build-up. The increase in temperature and pressure of the gas at the melt/substrate interface was calculated to confirm its role in air pocket formation. The plasma heating can improve wheel side contact thereby increasing the cooling rate of the ribbon during casting.
EFFECT OF MELT TEMPERATURE ON THE FORMATION OF AIR POCKETS DURING SPLAT QUENCHING
(1992-03-15)
WANG, WK
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KUO, CT
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CHIN, TS
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機械工程學系
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Department of Mechanical Engineering
The effect of melt temperature on the formation of air pockets at the contact surface of the ribbons was studied. An alloy with a melting point slightly higher than room temperature (320 K) was used and was heated to 353, 573 and 773 K, respectively, to investigate the thermal effect of the melt temperature on the gas. Under high casting velocity (20 m s-1) and extremely low melting temperature (353 K), the air pockets were slender and parallel to the casting direction. The liquid melts with a higher casting temperature (773 K) induced coarse air pockets at various casting velocities, and the air pockets were coarser than those induced by the pressure of the gas boundary layer only. The heat flow analysis showed that the local pressure of the entrapped gas, built up by the thermal effect and assuming constant volume, is far greater than the pressure by the gas-boundary layer effect. Thus the thermal effect of the liquid melt should be taken into account in the formation of air pockets during splat quenching.
INSITU REACTED TIB2-REINFORCED ALUMINA
(1992-11-15)
CHUANG, SC
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KUO, CT
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HO, CT
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LI, AK
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機械工程學系
In situ formation of TiB2 in Al2O3 matrix through the reaction of TiO2, boron and carbon has been studied. In hot-pressed samples, in addition to TiB2, TiC and Al2TiO5, were also found to be dispersed phases in Al2O3 matrix. However, in the case of pressureless-sintered samples, pure Al2O3/TiB2 composite with > 99% relative density can be obtained through a preheating step held at 1300-degrees-C for longer than 30 min and then sintering at a temperature above 1500-degrees-C. Pressureless-sintered composite containing 20 vol % TiB2 gives a flexural strength of 580 MPa and a fracture toughness of 7.2 MPa m1/2.
MICROSTRUCTURE DEVELOPMENT AND MECHANICAL-PROPERTIES OF Y2O3-DOPED TETRAGONAL ZRO2 POLYCRYSTALS AND MULLITE COMPOSITES
(1992-08-15)
CHUANG, SC
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KUO, CT
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LI, AK
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機械工程學系
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Department of Mechanical Engineering
Composites containing Y2O3-doped tetragonal ZrO2 polycrystals (Y-TZP) and mullite were prepared by adding Y-TZP powder to a silicon aluminate sol, which is the precursor of the mullite phase. After filtration and drying, the mixed powder was compacted and sintered at 1500-degrees-C in air for various lengths of time. The mullite particles were uniformly distributed in a Y-TZP matrix; energy-dispersive spectroscopy microanalysis indicated that the chemical composition of these particles ranged from 3Al2O3-2SiO2 to 2Al2O3-SiO2. Incorporating mullite particles in a Y-TZP matrix had two evident effects on the composites: first, the ZrO2 grain size was substantially increased; second, the fracture toughness of the composites showed a 50% increase (from 9 to 13.5 MPa m0.5). This increased toughness was due to the enhanced transformability of the tetragonal ZrO2 (t-ZrO2), which resulted mainly from the enlarged grain size and the increased tetragonality of the t-ZrO2.
THE ROLE OF CEMENTED WC SUBSTRATE MORPHOLOGY ON THE DIAMOND FILM GROWTH AND CRACKING RESISTANCE
(1992-05-01)
HUANG, TH
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KUO, CT
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LIN, TS
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機械工程學系
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Department of Mechanical Engineering
TRIBOLOGICAL BEHAVIOR OF CHEMICAL VAPOR-DEPOSITION DIAMOND FILMS ON VARIOUS CUTTING TOOLS
(1993-01-09)
HUANG, TH
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KUO, CT
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LIN, TS
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機械工程學系
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Department of Mechanical Engineering
Diamond films were deposited using a hot-filament-assisted chemical vapour deposition system on various cutting tool materials (i.e. cemented WC, sintered SiC, Si-Al-O-N, etc.). The friction coefficients of the films, the adhesion strengths of the films on the substrates, and the surface roughnesses of the substrates and the films were measured and their correlations analysed. The results indicate that the cutting performance of the diamond-coated inserts is strongly related to the adhesion strength and the friction coefficient of the film. Furthermore, the adhesion strength is also dependent upon the surface Co content and the surface roughness of the pretreated substrate, and the friction coefficient of the film is a function of the surface roughness and the quality and size of the diamond microcrystals. There exists an appropriate range of the substrate roughness values for an optimum adhesion strength. For the cemented WC substrates, the pretreatments of the substrate to remove the surface Co and to microscratch the surface to obtain an optimum surface roughness are essential to the growth of films with a lower friction coefficient and a better cutting performance. The cutting performance of the films on the cemented WC substrates is better than that of those on the sintered SiC or the Si-Al-O-N substrates. This is because there is a lower friction coefficient and a much higher adhesion strength of the film on the cemented WC substrates.
TRIBOLOGICAL BEHAVIORS OF THE DIAMOND-COATED CEMENTED CARBIDE TOOLS WITH VARIOUS COBALT CONTENTS
(1992-04-15)
HUANG, TH
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KUO, CT
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CHANG, CS
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KAO, CT
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WEN, HY
WEAR BEHAVIOR OF VARIOUS DIAMOND-COATED CUTTING TOOLS UNDER DIFFERENT DEPOSITION CONDITIONS
(1993-04-13)
HUANG, TH
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KUO, CT
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LIN, TS
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CHANG, CS
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材料科學與工程學系
A hot-filament-assisted chemical vapour deposition system was used to deposit diamond films on cemented carbide cutting tools with Co contents ranging from 6% to 22%. The surface roughness and friction coefficient of the films were measured under different deposition conditions. A block-on-ring tribotester and scanning electron microscopy were adopted to characterize the tribological behaviour and the film morphology. The results indicate that the cutting performance of the diamond-coated tools is closely related to the friction coefficient and surface roughness of the film and that the friction coefficient is a function of the surface roughness and film quality. For the 6% Co substrate the film deposited under 0.5% CH4 Concentration shows the best film quality and the lowest friction coefficient and its surface roughness is within the optimum range 0.06-0.25 mum; therefore it shows better cracking resistance and wear resistance.