• 한국재료학회지
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• 제27권10호
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• pp.563-568
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• 2017

In this study, the coating of an Al-Cr layer on the surface of a Zircaloy-4 alloy was carried out through plasma pretreatment coating and a laser surface melting process. Two different conditions for laser treatment, severe or minimal surface melting of the Zr alloy substrate, were applied to form the final coating. When there was significant surface melting of the Zr alloy, the solidification microstructure of the newly formed coating layer was mainly composed of needle-shaped $Al_3Zr$, Al(Cr) and $Al_7Cr$ phases. On the other hand, the solidification microstructure of the coating layer was mainly composed of Al(Cr) and $Al_7Cr$ phases when there was minimal surface melting of Zr base in the laser process. However, when the coating was maintained at $1100^{\circ}C$ for 2 hours, significant inter-diffusion occurred between the phases in the coating. As a result, the upper part of the coating layer was observed to mainly consist of $Al_3Zr$ and $Al_8Cr_5$ phases, regardless of the laser treatment conditions.

• 열처리공학회지
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• 제19권2호
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• pp.103-108
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• 2006

Microstructural evolution of Pt-aluminide coated Ni-based superalloy has been investigated with ductilization heat treatment. The Pt coat was prepared on the superalloy and then aluminide coating was conducted using a pack cementation process. Samples were heat-treated at $1050^{\circ}C$ for 2 hrs and the microstructure and element analysis were preformed. A various precipitated compounds were observed within the coating layer and the diffusion region in the Pt-aluminide coating and heat treatment, indicating that the bi-phase compounds of $PtAl_2$ and NiAl were performed during the Pt-aluminide coating, whereas $M_{23}C_6$, MC, $Ni_3Al$ and ${\sigma}$ phases were precipitated in the inter-diffusion region. The bi-phase compounds of $PtAl_2$ and NiAl were transformed into the single phase compound of $PtAl_2$ with the heat treatment, increasing the amount of carbide and ${\sigma}$ phase.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.200.1-200.1
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• 2016

Tungsten coatings on the graphite (CX-2320) were successfully deposited using the vacuum plasma spraying (VPS) method. An optimum coating procedure was developed and coating thicknesses of $409{\mu}m$ (without an interlayer) and $378{\mu}m$ (with an interlayer) were obtained with no cracks and no signs of delamination. The mechanical characteristics and microstructure of the tungsten coating layers were investigated using a Vickers hardness tester, FE-SEM, EDS, and XRD. The effect of a titanium interlayer on the properties of the tungsten coating was investigated. It was shown that the titanium interlayer prevented the diffusion of carbon to the tungsten layer, thereby suppressing the formation of tungsten carbide. Vickers hardness data yielded values that were 62.5 ~ 80.46% of those for bulk tungsten, indicating that tungsten coatings on graphite can be utilized as a plasma-facing material. High heat flux tests were performed by using thermal plasma with a maximum flux of $10MW/^2$. Vickers hardness after the heat flux test is performed to see a change in the mechanical properties. The formationof a tungsten carbide and the effect of the titanium interlayer for the diffusion barrier are investigated by using energy dispersion spectroscopy (EDS).

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 추계학술발표대회 개요집
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• pp.262-264
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• 2005

$Bi_{2}Sr_{2}CaCu_{2}O_{x}$(Bi-2212) and $Bi_{2}Sr_{2}Ca_{2}Cu_{3}O_{y}$(Bi-2223) high-$T_{c}$ superconductor(HTS) coating have been prepared by plasma spraying and heaat treatment. The Bi-2212 HTS coating later is synthesized through the peritectic reaction between Sr-Ca-Cu oxide coating layer and Bi-Cu oxide coating later, and $Bi_{2}Sr_{2}CaCu_{2}O_{y}$(Bi-2212) superconducting phase grow by partial melting process. The superconducting characteristic depends strongly on the conditions of the partial melting process. the Bi-2212 HTS layer consists of the whiskers grown in the diffusion direction. Above the 2212 layer, Bi-2223 phase and secondary phase was observed. The secondary phase is distributed uniformly over the whole surface. This is caused to the microcrack on the coatings surface. Despite everything, the film shows superconducting with an onset $T_{c}$ of about 115K. There are two changes steps. One changes (1step) at 115K is due to the diamagnetism of the Bi-2223 phase and the other changes (2step) at 78K is due to the diamagnetism of the Bi-2212 phase.

• 치위생과학회지
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• 제9권2호
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• pp.153-160
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• 2009

본 연구는 금속-도재 수복물 제작에 사용되는 Ni-Cr alloy와 Co-Cr alloy, 그리고 티타늄에 gold bonding agent를 도포하여 Au coating 층을 형성하였다. 각 시편의 절단면을 전자현미경으로 Au coating 층과 porcelain bonder, 그리고 불투명 도재간의 결합을 관찰하였고, 각 계면의 상태를 SEM/EDS 방법으로 조사하였다. 실험에서 사용된 재료와 방법의 범위 내에서 다음과 같은 결론을 얻었다. 1. Gold bonding agent를 사용하여 형성한 Au coating 층은 미세다공성을 가진 구조로 판단되었다. 2. Au coating 층과 porcelain bonder 그리고 불투명 도재간의 결합은 잘 일어나 보였다. 3. Au coating 층은 도재 소성과정에서 발생하는 산화층의 확산을 제한하는 것으로 관찰되었다.

• 한국표면공학회지
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• 제20권2호
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• pp.60-73
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• 1987

For the purpose of improving the cyclic oxidation resistance of Ni-base superalloy, Inconel 600, aluminide coating methods are studied. The formation rate of aluminide coating layers is measured as a function of time and pack composition to find out the optimum coating condition. The evaluation of cyclic oxidation is established by the change in weight, the microphotography and EPMA of cross sectional area during $200^{\circ}C\;{\leftrightarrow}\;950^{\circ}C\;and\;200^{\circ}C\;{\leftrightarrow}\;1100^{\circ}C$, respectively. The thickness of coating layer and weight gains are parabolic behavior in propotion to time and Al contents. In pack of low aluminum contents, 2 wt%, however, weight gain is decreased when activator, $NH_4Cl$ is higher than 2 wt%. The cyclic oxidation resistance of the coating carried out at 1100$^{\circ}C$ are superior to those of the coating diffusion-treated after pack cementation at 800$^{\circ}C$. Aluminide oxide, which is formed in external scale, is barrier to the cyclic oxidation.

• 한국세라믹학회지
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• 제34권5호
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• pp.512-518
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• 1997

The high temperature oxidation behaviors of titanium nitride films prepared by PACVD technique were studied in the temperature range of from 50$0^{\circ}C$ to 80$0^{\circ}C$ under air atmosphere. Ti0.88Al0.12N film, which showed the excellent microhardness from the previous work, was investigated on its oxidation resistance compared with pure TiN film. Ti-Al-N film showed superior oxidation resistance up to $700^{\circ}C$, whereas TiN film was fast oxidized into rutile TiO2 crystallites from at 50$0^{\circ}C$. It was found that an amorphous layer having AlxTiyOz formula was formed on the surface region due to outward diffusion of Al ions at the initial stage of oxidation. The amorphous oxide layer played a role as a barrier against oxygen diffusion, protected the remained nitride layer from further oxidation, and thus, resulted in the high oxidation resistive characteristics of Ti-Al-N film.

• 한국분말재료학회지
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• 제28권5호
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• pp.396-402
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• 2021

Stainless steel, a type of steel used for high-temperature parts, may cause damage when exposed to high temperatures, requiring additional coatings. In particular, the Cr₂O₃ product layer is unstable at 1000℃ and higher temperatures; therefore, it is necessary to improve the oxidation resistance. In this study, an aluminide (Fe₂Al₅ and FeAl₃) coating layer was formed on the surface of STS 630 specimens through Al diffusion coatings from 500℃ to 700℃ for up to 25 h. Because the coating layers of Fe₂Al₅ and FeAl₃ could not withstand temperatures above 1200℃, an Al₂O₃ coating layer is deposited on the surface through static oxidation treatment at 500℃ for 10 h. To confirm the ablation resistance of the resulting coating layer, dynamic flame exposure tests were conducted at 1350℃ for 5-15 min. Excellent oxidation resistance is observed in the coated base material beneath the aluminide layer. The conditions of the flame tests and coating are discussed in terms of microstructural variations.

• 한국표면공학회지
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• 제46권5호
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• pp.181-186
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• 2013

We performed plasma spraying for 2001 (Bi:Cu = 2:1), 0212 (Sr:Ca:Cu = 2:1:2) oxide powders. $Bi_2Sr_2CaCu_2Ox$ (2212) superconductor has been prepared by PMP-AT (partial melting process-annealing treatment). The 2212 phase is synthesized between Sr-Ca-Cu oxide coating layer (0212) and Bi-Cu oxide coating layer (2001) by movement of partial melted Bi on 2001 layer and the diffusion reaction (Cu, Sr, Ca) after PMP-AT. There are two different coating layers on joining process. The one is ABAB coating layers and the other is BAAB coating layers by arrangement of 2001 (A), 0212 (B) layers. We performed heat treatment these two different coating layers processes under same PMP-AT conditions. We obtained Bi-2212 superconducting layers at each experimental condition, and the result of MPMS, the critical temperature was showed about 78 K. But the microstructure images and result of EDS as each experimental variable were showed about the qualitatively different Bi-2212 superconducting phases. We also deduced the generation mechanism of Bi-2212 superconducting layer as a result of these experimental data, microstruc ture images, EDS data and phase diagram.

• 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.