• Tribology and Lubricants
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• v.39 no.1
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• pp.13-20
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• 2023

Large drill bits may face high hardness ore and high working pressure when working. To optimize the use effect of large drill bits and prolong the use time, it is necessary to add a layer of pressure-resistant, wear-resistant, and low-friction coating on the surface of the drill bit. In this study, CoCrNiAlTi high-entropy alloy coatings and CoCrNiAlTi (70 wt%)-TiC (30 wt%) composite coatings are successfully prepared on Q235 steel by plasma spraying. The CoCrNiAlTi (70 wt%)-TiC (30 wt%) coating consists of FCC solid solution and a small amount of TiC phase. The effect of TiC on the composition phase, microhardness, and elastic modulus of HEA coating is studied by X-ray diffractometer (XRD) and microhardness tester. The effect of TiC on the friction and wear properties of HEA coatings is investigated using a wear tester. By improving the process parameters, the metallurgical bonding between the coating and the substrate is well combined, and a coating without pores and cracks is obtained. The experimental results confirm that the microhardness, elastic modulus, and wear resistance of CoCrNiAlTi-TiC composite coating are better, and the friction coefficient is lower.

• Journal of the Korean Ceramic Society
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• v.32 no.2
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• pp.257-269
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• 1995

The TiC-Co/Al reaction-sintered products were prepared by the infiltration of various Co/Al metal mixture into the preform, and their microstructure, phases, and mechanical properties were investigated. With increasing the atomic ratio of Co/Al, tiC grain shape was changed from spherical to platelet particles, and the grain size increased. The crystalline phases found in the liquid matrix formed by the infiltration of Co/Al metal mixture were determined to be Al5Co2 and AlCo by EDS and XRD, and the two crystalline phases were located dominantly between TiC grains, when the Co/Al atomic ratio was lower than an unity. There was a tendency that the density, bending strength and fracture toughness increase with Co/Al atomic ratio until the infiltrated metal was 100% Co. The maximum value was achieved by the composition containing 100% Co infiltrated metal. The Vickers hardness decreased as Co/Al atomic ratio increased.

• Journal of Welding and Joining
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• v.18 no.5
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• pp.105-111
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• 2000

The wear behavior of thermal sprayed AlSiMg-40TiC composite coatings were studied as a function of load and sliding velocity under unlubricated conditions. Experiments were performed using a block-on-ring(WC-6wt%/Co, Hv 1500) type. The tests were carried out a various load(30∼ 125.5N) and sliding velocity(0.5∼2.0m/s). Three wear rate regions were observed in the AlSiMg-40TiC composite coatings. The wear rate in region I at low load (less then 8N( were less than 1×{TEX}$10^{-5}${/TEX}㎣/m. Low wear rates in region I resulted from the load-bearing capacity of TiC particles. The transition from region I to II occurred when the applied load exceeded the fracture and pull-out strength of the particles. The TiC fractured particles trapped between the specimen and the counterface acted as third-body abrasive wear. The subsurface layer worn surface in region II was composed of the mechanically mixed layer (MML). The wear rate increase abruptly above a critical load (region III). The high wear rate in region III was induced by frictional temperature and involves massive surface damage.

• Applied Chemistry for Engineering
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• v.7 no.6
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• pp.1192-1203
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• 1996

$Al_2O_3-TiO_2$ composite oxide adsorbents which could be applied in high-temperature water were prepared by hydrolysis of aluminum and titanium alkoxide. The prepared adsorbents were calcined at $600{\sim}1400^{\circ}C$ and in order to investigate the various properties - the transition of crystals, thermal properties, and specific surface area, X-ray diffractometry, thermal analysis, FT-IR, SEM and BET method were employed. And the $Co^{2+}$ adsorption characteristics of these adsorbents in high-temperature water were investigated by batch adsorption experiment in a stirred autoclave. Since the adsorption of $Co^{2+}$ on the $Al_2O_3-TiO_2$ adsorbents was irreversible endothermic in the temperature range of $150{\sim}250^{\circ}C$, the standard enthalpy changes of 26, 43, and 80 mol% of $TiO_2$ on $Al_2O_3$ were in the range of $16.5{\sim}26.0kJ{\cdot}mol^{-1}$. The adsorbent of 26 mol% of $TiO_2$ on $Al_2O_3$ which was calcined at $600^{\circ}C$ for 2 hours showed the adsorption amount of $0.1674meq{\cdot}g^{-1}$ in the high temperature water at $250^{\circ}C$.

• Journal of Korea Foundry Society
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• v.15 no.4
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• pp.368-376
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• 1995

An Al-composite material was fabricated with using the rheocompocasting process and the microstructure of the Al-Cu/SiCp composite material was investigated depending on the stirring times and the amount of Ti additions. The distribution of SiC dispersion shows the good result at the stirring time of 30 min. The degree of microdistribution of the $Al_2Cu$ and SiCp is improved when the amount of Ti addition is increased. At the compositon of 0.3%Ti, the primary solid is the compound of $Al_3Ti$ and no exist of the SiCp and $Al_2Cu$ phase around the primary $Al_3Ti$. In the process of compositization, SiCp is found at the primary and final solid parts and is found at the final solid part after remelting. $Al_2Cu$ and SiCp are distributed around and outside of dendrite or independently after remelting, which is different from the process of compositization.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.7
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• pp.1713-1721
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• 1994

Intermetallic-matrix composites(IMCs) have the potential of combing matrix properties of oxidation resistance and high temperature stability with reinforcement properties of high specific strength and modulus. One of the major limiting factors for successful applications of these composite at high temperatures is the formation of interfacial reactions between matrix and ceramic reinforcement during composite process and during service. The purpose of the present investigation is to develop a better understanding of the nature of creep fracture mechanisms in a $Ni_{3}Al$ composite reinforced with both $TiB_{2}$ and SiC particulates. Emphasis is placed in the roles of the products of the reactions in determining the creep lifetime of the composite. In the present study, creep rupture specimens were tested under constant ranging from 180 to 350 MPa in vacuum at $760^{\cric}C$. The experimental data reveal that the stress exponent for power law creep for the composite is 3.5, a value close to that for unreinforced $Ni_{3}Al$. The microstructural observations reveal that most of the cavities lie on the grain boundaries of the $Ni_{3}Al$ matrix as opposed to the large $TiB_{2}/Ni_{3}Al$ interfaces, suggesting that cavities nucleate at fine carbides that lie in the $Ni_{3}Al$ grain boundaries as a result of the decomposition of the $SiC_{p}$. This observation accounts for the longer rupture times for the monolicthic $Ni_{3}Al$ as compared to those for the $Ni_{3}Al/SiC_{p}/TiB_{2} IMC$. Finally, it is suggested that creep deformation in matrix appears to dominate the rupture process for monolithic $Ni_{3}Al$, whereas growth and coalescence of cavities appears to dominate the rupture process for the composite.

• Journal of Korea Foundry Society
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• v.20 no.4
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• pp.254-259
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• 2000

Metal matrix composites(MMCs) reinforced with hard particles have many potential application in aerospace structures, auto parts, semiconductor package, heat resistant panels, wear resistant materials and so on. In this work, the effect of SiC partioel sizes(50 and 100 ${\mu}m$) and additional elements such as Si, Cu and Ti on the microstructure and the wear property of $Al-5Mg-X(Si,Cu,Ti)/SiC_p$ composites produced by pressureless infiltration method have been investigated using optical microscopy, scanning eletron microcopy(SEM) with EDS(energy dispersive spectrometry), hardness test, X-ray diffractometer(XRD) and wear test. In present study, the sound $Al-5Mg-X(Si,Cu,Ti)/SiC_p$(50 and 100 ${\mu}m$) composites were fabricated by pressureless infiltration method. The $Al-5Mg-0.3Si-O.1Cu-O.1Ti/SiC_p$ composite with $50 {\mu}m$ size of SiC particle has higher hardness and better wear property than any other composite with $100{\mu}m$ size of SiC particle produced by pressureless infiltration method. The hardness and wear property of $Al-5Mg/SiC_p$(50 and 100 ${\mu}m$) composites were enhanced by the addition of Si, Cu and Ti in Al-5%Mg matrix alloy.

• Journal of Powder Materials
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• v.9 no.6
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• pp.455-462
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• 2002

The microstructures and properties of TiC dispersed nickel-base alloy were studied in this work. The alloy prepared by powder metallurgical processing was solution treated, 1st-aged at $880^{\circ}C$ for 16 hours, and then 2nd-aged at $760^{\circ}C$ for 4 hours. Microstucture of sintered specimen showed that TiC particles are uniformly dispersed in Ni base alloy. In the specimen aged at $880^{\circ}C$ for 8 hours, the fine $\gammaNi_3$(Al,Ti) precipitates with round shape are observed and the very fine $\gammaNi_3$(Al,Ti) particles with round shape are precipitated in the specimen aged at $760^{\circ}C$ for 4 hours. The presence of ${\gamma}$precipitates in TiC/Ni base alloy increased the hardness and wear resistance of the specimen. The hardness and wear resistance of the Ni-base with TiC are higher than those of conventional Ni-base superalloy X-750 because of dispersion strengthening of TiC particles. The hardness, transverse rupture strength and resistance of the specimen 2nd-aged at $760^{\circ}C$ for 4 hours are higher than those of 1st-aged specimen due to ultrafine $\gammaNi_3$(Al,Ti) precipitates.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.232-233
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• 2007

We manufactured Liquid Crystal Polymer (LCP) and (1-x)CaTiO3-xLaAlO3 (CT-LA) ceramic composites and investigated dielectric properties to use as embedded capacitor in printed circuit boards and replace LTCC substrate. The dielectric properties of these composites are varied with volume fraction of CT-LA and ratios of CT/LA. Dielectric constants are in the range of 3~15. In addition, we could get low TCC and High Q value that could not achieve in other ceramic-polymer composites. Especially, in composite with x=0.01 and 30 vol% CT-LA, the dieletric constant and Q-value are 10 and 200, respectively. And more TCC is $-28{\sim}300ppm/^{\circ}C$ in the temperature range of $-55{\sim}125^{\circ}C$. We think that this composites can be used high-Q substrate material like LTCC and embedded temperature compensation capacitor in printed circuit boards.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1209-1210
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• 2006

A novel sintering process is proposed for bonding of $BaTiO_3$ and $Al_2O_3$ layers. Common commercial glass was used and infilterated among filler particles. As the kind of commercial glass, the phenomenon of the infilteration is different. Although Sud-1140 glass forms a glass/filler composite, it is not completely infilterated into the filler particles at $900^{\circ}C$. However as the increase of sintering temperature the infilteration of glass was improved. In this study, GA-1 and GA-12 glasses were infilterated the more than Sud-1140 glass. However, they are reacted by $BaTiO_3$ layer. The results of the experiment show that constrained sintering and the co-firing of the different materials were possible for glass infilteration using Sud-1140 glass at $1000^{\circ}C$.