• 한국분말재료학회지
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• 제20권6호
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• pp.460-466
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• 2013

4 mol% Yttria-stabilized zirconia (4YSZ) coatings with $200{\mu}m$ thick are fabricated by Electron Beam Physical Vapor Deposition (EB-PVD) for thermal barrier coating (TBC). $150{\mu}m$ of NiCrAlY based bond coat is prepared by conventional APS (Air Plasma Spray) method on the NiCrCoAl alloy substrate before deposition of top coating. 4 mol% YSZ top coating shows typical tetragonal phase and columnar structure due to vapor phase deposition process. The adhesion strength of coating is measured about 40 MPa. There is no delamination or cracking of coatings after thermal cyclic fatigue and shock test at $850^{\circ}C$.

• 한국표면공학회지
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• 제42권2호
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• pp.86-94
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• 2009

Various types of multilayer coatings including Al/$Al_2O_3$ structure have been prepared on Nd-Fe-B permanent magnet to modify the morphology of the coating and to enhance the corrosion resistance of the magnet. Magnetron sputtering has been employed to make the multilayer coatings. $Al_2O_3$sputtering conditions were optimized in reactive sputtering by varying the deposition parameters. The formation of $Al_2O_3$ film was confirmed from the binding energy shift measured by electron spectroscopy for chemical analysis. 3 types of coating structures were designed and prepared by magnetron sputtering. The coating structures consist of (1) single Al coating, (2) modified coatings having oxide or plasma treated layer in the middle of coating structure, and (3) Al/$Al_2O_3$ multilayer coatings. Surface and cross-sectional morphologies showed that Al/$Al_2O_3$ multilayer grew as a layered structure, and that very compact Zone 3 like structure were formed. X-ray diffraction peak showed that the crystal orientations of multilayer coatings were similar to that of the bulk powder pattern. Hardness increased drastically when the Al thickness was around 1im in the Al/$Al_2O_3$ multilayer. From the salt spray test and pressure cooker test, it has been shown that the multilayer coatings showed good corrosion resistance compared to Al single or modified layer coatings.

• 비파괴검사학회지
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• 제29권5호
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• pp.450-457
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• 2009

열차폐 코팅 시편에 대하여 열충격을 주기적으로 가한 후 발생하는 결함을 관찰하였다. 실험에 사용 된 열차폐 코팅 시편은 인코넬-738로 제작된 모재 위에 CoNiCrAlY 본드 코팅층과 $ZrO_2-8wt%Y_2O_3$ 세라믹탑 코팅층이 플라즈마 용사 방법으로 올려진 형태로 되어있다. 열충격 시험은 $1000^{\circ}C$의 고온으로 가열했다가 상온으로 급격하게 냉각시키는 가혹한 조건으로 실행되었고, 사이클 수가 증가함에 따라 열충격의 피로도 또한 증가하였다. 시험후 시편 내부의 미세 조직 변화와 결함을 전자현미경으로 관찰하고, 시편의 기계적인 특성을 측정하여 그 변화 양상을 살펴보았다. 열충격 주기실험후 본드 코팅층과 세라믹 탑 코팅층 사이에 발생하는 TGO 산화물층에 대한 변화 양상과 이에 대한 와전류 신호를 측정하여 TGO층 성장 거동의 비파괴적인 평가를 위한 실험을 진행하였다. 본 연구를 통하여 마이크로 단위의 TGO층에 대한 와전류검사의 적용 가능성을 확인하고 열차폐 코팅의 수명을 예측할 수 있는 가능성을 제시하였다.

• 한국세라믹학회지
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• 제54권6호
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• pp.492-498
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• 2017

A thermal barrier coating (TBC) with self-healing property for cracks was proposed to improve reliability during gas turbine operation, including structural design. Effect of healing agent on crack propagation behavior in TBCs with and without buffer layer was investigated through furnace cyclic test (FCT). Molybdenum disilicide ($MoSi_2$) was used as the healing agent; it was encapsulated using a mixture of tetraethyl orthosilicate and sodium methoxide. Buffer layers with composition ratios of 90 : 10 and 80 : 20 wt%, using yttria stabilized zirconia and $MoSi_2$, respectively, were prepared by air plasma spray process. After generating artificial cracks in TBC samples by using Vickers indentation, FCTs were conducted at $1100^{\circ}C$ for a dwell time of 40 min., followed by natural air cooling for 20 min. at room temperature. The cracks were healed in the buffer layer with the healing agent of $MoSi_2$, and it was found that the thermal reliability of TBC can be enhanced by introducing the buffer layer with healing agent in the top coat.

• 한국표면공학회지
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• 제31권1호
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• pp.12-23
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• 1998

The Thermal Barrier Coating(TBC) has been used to improve the heat barrier and tribological properties of the aircraft engine and the automobile engine in high temperature. Especially, the high temperature tribological propertied of the cylinder haed and the piston crown of diesel engine was emphasized. Therefore, the purpose of this work was to evaluate the microstructure, tribological propeer in high tempearmal shock resistance and bonding strength of five layer functionally gradient TBC for the applications. The five layerwere composed with 100% ceramic insulating later, 75(ceramic):25 (metal) layer, 50:50 layer, 25:75 layer and 100% metal bonding layer to redude the thermal stress. the YSL and MSL poweders were the insulation ceramics powers. The NiCrAly, Inconel625 and SUS powders were the bonding and mixingg powders for plasma spray process. According to the result of high temperature wear test, the wera resistance of YSZ/NiCrAlY siytem was most out standing at 600 and $800^{\circ}C$. At $400^{\circ}C$, the wear resistance of YSZ/Inconel system was better than others. Wear volume at other temperature because of the low temperature degration of zirconia. The thermal shock mechanism of 5 later is the vertical crack gegration in insulating layer. this means that the initial cracks were generated in the top layer, and then developed into the composite layers during thermal shock test. Finally, these cracks werereached to the interface of coating and substrate and also, these vertioal cracks join with the horizontal cracks of the each layers. The bonding strength of YSZ/NiCrAlY and YSZ/Inconel 5 layer system is better than other 5layer systems. The theramal shock resistance of thermal barrier coating s with 5 layer system is better than that of 3 layers and 2 layers.

• 열처리공학회지
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• 제30권6호
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• pp.264-270
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• 2017

본 연구에서는 다이아몬드의 기계적 화학적 연마(MCP) 에 주목하여 기존에 알려진 다이아몬드 가공연마판을 주물 또는 파우더 소결 방식이 아닌 플라즈마 열분사 기법을 통하여 경제성이 높게 제작하고 이를 상용화 하고자 하였다. 저렴한 주철 모재에 연성이 높고 밀착성이 우수한 Al을 중간 코팅층으로 코팅하고, 상부 코팅층으로 다이아몬드와 화학반응을 하게 되는 Fe-Cr-Ni 및 Ti 코팅층을 플라즈마로 코팅하여 다이아몬드 연마판을 제작하였다. 또한, 물리적인 코팅방법인 플라즈마 열분사 코팅층의 밀착력을 개선 하기 위하여 $550^{\circ}C$ 6시간 동안 열처리를 수행하고 모재와 Al 코팅층 사이에 약 $5{\mu}m$ 정도의 확산층을 형성하여 밀착력을 개선할 수 있었다.

• 한국재료학회지
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• 제28권3호
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• pp.135-141
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• 2018

Stainless steel is being used in various industries such as automobile and aerospace for its cheap manufacturing cost and excellent mechanical properties. However, stainless steel failed to stably protect a specimen with a $Cr_2O_3$ protective layer at temperatures above $1000^{\circ}C$. Thus, improving the high temperature flame resistance of the specimen through additional surface coating was needed. In this study, multilayer coatings of YSZ and $Al_2O_3$ were performed on SUS 304 specimens using pack cementation coatings and thermal plasma spray. The multilayer coated specimen showed enhanced thermal properties due to the coated layers. The microstructures and phase stability are discussed together with flame conditions at $1350^{\circ}C$.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.603-607
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• 2009

액체로켓엔진 연소기의 내벽에 사용하기 위한 니켈/크롬 도금 공정 개발을 수행하였다. 열충격 시험을 통해 니켈 도금 조건을 선별하였고 니켈/크롬 도금이 수행된 축소형 연소기의 연소시험을 통해 도금 층의 내구성 검증을 수행하였다. 시험결과 도금 층의 균열 및 박리는 발견되지 않았고, 이 결과로부터 현재 사용중인 대기 플라즈마 용사된 세라믹 코팅의 대안으로 니켈/크롬 도금을 액체로켓엔진 연소기에 사용할 수 있으리라 사료된다.

• Journal of Periodontal and Implant Science
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• 제25권2호
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• pp.418-437
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• 1995

The effect of the hydroxyapatite coatings on Titanium implants has been the subject of recent investigations. So far, the use of HA coating remains substantially controversial.This study was aimed to evaluate histologically the bone healing patterns around titanium plasm sprayed(TPS) amd HA-coated implant after implantation into the femur neck of ten adult dogs. After implantation, animals were sacrificed at the intervals of 2,4,6,8 and 12 weeks.The fluorescent dyes were injected on the postoperative 4th and 12th week into the animals supposed to be killed at the 12th week. The morphology and direction of new bone formation was similar in both TPS and HA-coated implants.There was a tendency toward more bone formation in the cortical bone area than in the cancellous bone area. Histologically,in the interface of the HA-coated implants, bone response and bone maturation was faster, compared to the TPS implants in the 2nd and 4th week. By fluorescent microscopy, new bone formation was active in the 4th week around both implants and was directed from the periosteum overlying cortical bone to the cancellous bone. These results suggest that the bone formation and maturation is faster during the early healing stage in the interface of the HA-coated implant and where the cortical bone quality is poor, HA coated implant is superior to the TPS implant in the early phase of new bone formation.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.190-190
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• 2012

전북대학교 고온 플라즈마 응용 연구 센터는 교육과학기술부 기초연구사업 중 고가연구장비 구축사업의 일환으로 소재공정용 다목적 100 kW 플라즈마 발생장치를 구축하고 있다. 100kW급 ICP (RF)형 플라즈마 발생장치는 RF 전력 인출이 이중으로 되어있어 한쪽에서는 수~수십 um 크기의 금속, 세라믹 등 고융점 원료분말을 순간적으로 용해, 기화 및 분해시키고 이들 기화 또는 분해된 증기를 급랭시키는 과정에서 초미분(<1 um)을 합성하는 플라즈마 합성법 연구가 가능하도록 RF 플라즈마 분말 합성 시스템이 연결되어 있고 다른 한쪽으로는 진공 챔버 내에서 고온 고속의 RF 플라즈마 불꽃을 형성 한 후 RF 플라즈마의 축 방향으로 반응성 가스 및 코팅 대상 물질을 주입하여 코팅 할 수 있는 열플라즈마 용사코팅 시스템이 연결되어 있는 다목적 연구 장치이다. 본 장치는 100 kW급 RF 전원 공급기와 유도결합형 플라즈마 토치, 플라즈마 분말 합성 부, 플라즈마 코팅 및 반응성 증착부, 가스 공급부, 냉각수 공급부, 전기 계장/제어부로 구성되어 있다.