• Journal of Ceramic Processing Research
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• 제20권5호
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• pp.499-504
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• 2019

The effect of coating thickness on the contact fatigue and wear of thermal barrier coatings (TBCs) are investigated in this study. The same bondcoat material thickness (250 ㎛) are used for each sample, which allows the effect of the coating thickness of the topcoat to be investigated. TBCs with different coating thicknesses (200, 400, and 600 ㎛) are prepared by changing processing parameters such as the feeding rate of the feedstock, spraying speed, and spraying distance during APS(air plasma spray) coating. The damage size on the surface are strongly affected by the coating thickness effect. Although the damage size from contact fatigue using a spherical indenter diminish at a TBC of 200 ㎛, a high wear resistance such as a low friction coefficient and little mass change are found at a TBC of 600 ㎛. These results indicate that the coating thickness strongly affects the mechanical behavior in TBCs during gas turbine operation.

• The Korean Journal of Ceramics
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• 제4권4호
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• pp.340-344
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• 1998

Failure mechanisms were investigated for the two layer thermal barrier coatings consisting of NiCrAlY bond coat and $ZrO_2$-8wt.% $Y_2O_3$ ceramic coating during cyclic oxidation. $Al_2O_3$ developed at the ceramic coating/bond coat interface first, followed by the Cr/Ni rich oxides such as $NiCr_2O_4$ and $Ni(Al, Cr)_2O_4$ during cyclic oxidation. It was observed that the spalling of ceramic coatings took place primarily within the NiCrAlY bond coat oxidation products or at the interface between the bond coat oxidation products and zirconia based ceramic coating or the bond coat. It was also observed that the fracture within these oxidation products occurred with the formation of $Ni(Cr, Al)_2O_4$ spinel or Cr/Ni rich oxides. It was therefore concluded that the formation of these oxides was a life-limiting event for the thermal barrier coatings.

• 전기학회논문지
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• 제66권11호
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• pp.1647-1650
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• 2017

Bus bars are used in place of cables because they can carry more electrical energy with the same volume of conductors. This paper deals with the electrical properties of ceramic coating material for busbars. A ceramic coated samples were prepared for the electrical properties test. There are two types of samples. One is a sample without degradation, and the other is a sample degraded for 30 days. Four electrical properties tests were carried out in accordance with domestic standards. Four electrical characteristics tests are AC dielectric breakdown, V-t, lighting impulse dielectric breakdown, and discharge arc. Both samples showed excellent electrical properties, and the ceramic coating material is very good insulating materials for bus bar.

• 대한기계학회논문집
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• 제17권12호
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• pp.3083-3093
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• 1993

Friction and wear at ceramic coated surfaces of aluminum alloy were experimentally studied using a Ring-on-Block wear test machine. Ceramic materials coated on aluminum alloy surfaces were WC, CrC, $Al_{2}O_{3}$ by a plasma spray; and $Al_{2}O_{3}$,$Al_{2}SiO_{5}$, $Na_{2}B_{4}O_{7}$,$Na_{4}P_{2}O_{7}$, and $Al_{2}O_{3}-ZrO_{2}$ composite coating by an Anodic Spark Depositon. They were tested under the sliding wet contact and compared with aluminum alloys and steels. Test results showed that ceramic coated surfaces, in general, have better anti-wear property than those of aluminum alloys due to increase in the surface hardness ; however, they also showed higher coefficients of friction and changes in wear mechanisms, resulting in brittle fractures.

• 한국재료학회지
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• 제8권6호
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• pp.505-512
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• 1998

플라즈마 용사법을이용하여 AISI 316 스테인레스 금속모재에 0.1mm 두께의 $NiCrAlCoY_{2}O_{3}$금속 결합층과 0.3mm 두께의 $ZrO_{2}(8wt%Y_{2}O_3$) 세라믹층으로 구성된 이층 단열코팅층을 제조하였다. 코팅층의 미세조직, 금속결합층의 산화를 고찰하였으며, $900^{\circ}C$에서 등은 시험과 열반복시험 후, 접합강도시험을 통하여 코팅층의 단사정 상은 열처리시간이 길어질수록 약간 증가하였다. 또한 비변태성 t'의 c/a는 용사상태에서 1.0099이였으며, 100시간 열처리 후에는 1.0115로 약간 증가하였다. 그리고 용사층의 접합강도는 열처리 시간이 길어질수록 감소하였다. 등온열처리 후에는 1.0115로 약간 증가하였다. 그리고 용사층 의 접합강도는 열처리 시간이 길어질수록 감소하였다. 등온열처리 후, 파괴는 주로 세라믹층에서 일어났으며, 반복 열처리되 시편에서는 10회 이후 대부분 금속결합층/세라믹층의 계면에서 일어났다.

• 대한기계학회논문집A
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• 제21권10호
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• pp.1674-1682
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• 1997

Fatigue tests were performed to investigate the effect of ceramic coatings as in TiN and TiCN on fatigue crack growth properties of ceramic coated 1Cr-1Mo-0.25V steel with different coating thickness in laboratory air conditions. The experimental results are described with respect to a Paris equation, da/dN=C(.DELTA.K)$^{m}$ , where the crack growth rate of coated specimens provided as similar growth rate as that of the uncoated specimen regardless of coating thickness. Furthermore, it was observed that the type of coating layer had virtually no effect on crack growth rate in the full region of stress intensity factor range. And it was also appeared that the final crack length of TiCN coated specimens was short compared to that of TiN coated, and the substrate specimens, in which it was inferred due to lowering the toughness of coated material from high hardness of TiCN coating layer itself.

• 한국세라믹학회지
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• 제49권1호
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• pp.95-99
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• 2012

Silicon carbide ceramics are used for oxidation resistive coating films due to their excellent properties like high strength, good oxidation resistance, and good abrasion resistance, but they have poor formability and are prepared by vapor process which is complicated, costly, and sometimes hazardous. In this study, preparation of silicon carbide coating film by liquid process using polymer precursor was attempted. Coating film was prepared by dip coating on substrate followed by heat treatment in argon at $1200^{\circ}C$. By changing the dipping speed, the thickness was controlled. The effects of plasticizer, binder, or fiber addition on suppression of crack generation in the polymer and ceramic films were examined. It was found that fiber additives was effective for suppressing crack generation.

• 한국해양공학회지
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• 제15권3호
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• pp.69-74
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• 2001

This paper was to investigate of a adhesiveness for the plasma sprayed coating materials did salt spray by acoustic emission method in tensile loadings. The powders used for the coating were nickel aluminum composite powder Ni-4.5wt.%Al and titanium dioxide powder $TiO_2$. These powders were coated on a carbon steel S45C by plasma spray method. The result solution was a 5% NaCl and the slat spray times were 2, 5 and 10 hours respectively. The salt solution penetrated into the surface of the substrate through pore of the coating layer built in the process of plasma spay. Corrosion productions formed on the surface of substrate. The adhesiveness between the substrate and the coating layer is weaken by corrosion and the exfoliation initiated chiefly at the corrosion surface of the substrate. The AE events and energy of the corroded coating specimens decreased as the salt spray times increased.

• 동력기계공학회지
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• 제2권3호
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• pp.49-54
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• 1998

This paper is investigated of hardness and adhesiveness of plasma sprayed coating steels by AE(Acoustic Emission) testing when loading a tensile. AE Parameters used are Event, Count, Energy and Amplitude. Test specimens are carbon steel(S45C) with sprayed coating layers of Ni-4.5wt.%Al(bond coating) and $TiO_2$(top coating), and carry out heat treatment at $800^{\circ}C\;and\;1000^{\circ}C$, respectively. The micro-hardness of the heat treatment specimen have been improved more than that of non-heat treatment. On the tensile test, the process and occurence of the exfoliation of the sprayed coating layer can be estimated by AE Characteristics of AE parameters, such as event, count, amplitude and energy, on the layer exfoliation are shown the similar aspects. The exfoliation of bond coating occure at about 20% of strain and top coating is about 5% of strain.

• 한국세라믹학회지
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• 제36권6호
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• pp.571-576
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• 1999

This paper describes both electromagnetic properties and electromagnetic-wave absorbind (EMA) characteristics of the radar absorbing coating materials in the microwave frequencies. The coating materials are prepared by mixing ferrite powder with epoxy resin polymers. The electromagnetic property and the EMA characteristics of the coating materials are measured in the frequency ranges between 0.2 GHz and 15GHz using the S-parameter method. The results show that the typical coating material has ({{{{ {μ }`_{r } ^{' } }} of about 2 and ({{{{ { ε}`_{r } ^{' } }} of about 4. And the coating materials have a little EMA characteristics in the frequency from 4 to 6 GHz and more improved EMA characteristics around 12 GHz And it is desirable for improvement of the EMA characteristics of the coating materials to properly select electromagnetic properties of constitutional materials inthe interesting frequency ranges.