• Journal of the Korean Ceramic Society
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• v.37 no.9
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• pp.839-846
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• 2000

통전활성 소결법을 이용하여 단상의 세라믹스(PSZ) 및 금속(NiCrAlY)과 PSZ/NiCrAlY 복합체를 각 소결온도에서 제조하였으며, 이에 대한 특성평가는 개량형 소형펀치 시험법을 이용하여 수행하였다. 복합체의 밀도 및 경도에 미치는 소결온도의 영향은 NiCrAlY의 부피분율 증가에 따라 감소되었으며, 중간조성에서의 밀도 및 경도는 연속적인 변화를 나타내었다. 파괴인성의 변화에서는 60vol%-NiCrAlY 이상의 조성에서 급격한 증가를 나타내었으며, 짧은 소결시간 및 빠른 승온속도 등 통전활성 소결법의 장점에 의해 단상의 PSZ에서도 10 MPa.m$^{1}$2/ 의 높은 파괴인성 값을 얻을 수 있었다. PSZ/NiCrAlY 복합체에서의 특성은 소결온도와 NiCrAlY의 부피분율에 의해 지배적으로 영향을 받았으며, 단상의 PSZ은 전형적인 취성거동을 나타내었고 80vol%-NiCrAlY 까지의 복합체에서는 부분적인 취성 및 소성거동을 함께 나타내었다. 각 소결체에서 최고의 특성을 나타내고 소결온도는 단상의 PSZ 경우인 140$0^{\circ}C$에서부터 단상의 NiCrAlY 경우인 120$0^{\circ}C$까지 최대 20$0^{\circ}C$의 차이를 나타내었으며, PSZ과 NiCrAlY의 조성비에 따라서 연속적인 변화를 보였다.

• Korean Journal of Materials Research
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• v.12 no.11
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• pp.845-849
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• 2002

Alloys of $Fe_3$Al, $Fe_3$Al-6Cr, $Fe_3$Al-4Cr-1Mo, $Ni_3$Al, and $Ni_3$Al-2.8Cr were oxidized at $1000^{\circ}C$ in air, and the oxide scales formed were studied using XRD. SEM, EPMA, and TEM. The oxide scales that formed on $Fe_3$Al-based alloys consisted primarily of $\alpha$-$Al_2$$O_3$ containing a small amount of dissolved Fe and Cr ions, whereas those that formed on $Ni_3$Al-based alloys consisted primarily of $\alpha$-$Al_2$$O_3$, together with a small amount of $NiAl_2$$O_4$, NiO and dissolved Cr ions. For the entire alloys tested, nonadherent oxide scales formed, and voids were inevitably existed at the scale-matrix interface.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.421-425
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• 2009

A study has been performed to investigate the thermo-mechanical effects of thermal barrier coating on liquid rocket regenerative cooling chamber using finite element analysis. Two kinds of thermal barrier coatings were studied on the same loading condition: first, NiCrAlY-$ZrO_2$, coating which is currently applied to the developing combustion chamber and second, Ni-Cr coating which might be applied in the future. Analysis results showed that NiCrAlY-$ZrO_2$ coating has better decreasing effect of temperature than the Ni-Cr coating. As a results, temperature and deformation of the cooling channel in the NiCrAlY-$ZrO_2$ coating were also less than those of the Ni-Cr coating. The Ni-Cr coating has no effect on a structural stability of the outer jacket but the NiCrAlY-$ZrO_2$ coating reduced the effective stress of the outer jacket and enhanced the structural stability of the chamber.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2003.10a
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• pp.65-66
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• 2003

• Journal of the Korean institute of surface engineering
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• v.35 no.2
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• pp.101-106
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• 2002

The microstructural changes of $NiCrAlY/ZrO_2$-$Y_2$$O_3$ composite coatings that were manufactured by air-plasma-spraying were investigated using XRD and SEM/EDS. The as-sprayed microstructure consisted of (Ni,Cr)-rich regions, ($ZrO_2$-$Y_2$$O_3$)-rich regions, and $Al_2$$O_3$-rich layers that were formed during spraying owing to the oxidation of Al in NiCrAlY. During oxidation between 900 and $1100^{\circ}C$ in air, Cr in the (Ni,Cr)-rich regions diffused toward the $Al_2$$O_3$-rich layers, and oxidized to be dissolved in $A1_2$$O_3$-rich layers. The oxidation of Ni in the (Ni,Cr)-rich regions was less distinct, except at the outer surface of the coating.

• Journal of the Korean institute of surface engineering
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• v.39 no.3
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• pp.129-136
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• 2006

The high velocity oxy-fuel sprayed coatings of 38Ni-23Co-20Cr-11Al-3Y-5Ta, 25Ni-34Co-20Cr-11Al-3Y-2Re and 32Ni-34.5Co-22Cr-11Al-0.5Ir (in wt%) were oxidized at 1000 and $1100^{\circ}C$ in air in order to find the alloying effect of Ta, Re and Ir on the oxidation properties of the NiCoCrAlY-base coatings. The primary phase of the coatings was $Ni_3Al$. The oxides formed on the coatings consisted primarily of ${\alpha}-Al_2O_3$, together with some $CoCr_2O_4,\;CoAl_2O_4$, and $Al_5Y_3O_{12}$. Tantalum oxidized to $Ta_2O_5$ and $Ta_2O_{22}$. However, no oxides of Re and Ir were detected by XRD owing to their thermodynamic inertness and/or their small amount.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.219-219
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• 2003

HVOF(High Velocity Oxygen Fuel)법을 사용한 MCrAlY(M=Ni, Co, Fe)계 열차폐 코팅(thermal barrier coating)은 열기관 내부의 극심한 환경 부하에 대해 구조물 표면에 열적, 화학적 장벽을 형성함으로써 구조물의 내구성을 향상시킨다 이와 동시에 열차폐 효과는 구조물의 온도상승 없이 내부 가동 온도를 높일 수 있게 함으로써 열효율을 상승시키고 연료 효율을 높여 가동비용 절감을 이룰 수 있는 동시에 고 연소를 통한 오염원의 배출을 감소시킬 수 있다. 본 연구에서는 $H_2O$$_2$=5:1 분위기 하에서 HVOF법을 사용하여 Hastelloy-X 기판위에 125$\mu\textrm{m}$의 두께로 다음 5종류의 (Ni, Co, Cr)계 MCrAlY 코팅을 용사시켰다. 준비된 (Ni, Co)-Cr-Al-(Y, Ta, Re), (Ni, Co)-Cr-Al-(Y, Re), (Ni, Co)-Cr-Al-(Y, Ta), (Ni, Co)-Cr-Al-Y, (Ni,Co)-Cr-Al-Ir 코팅시편에 대한 산화성질을 조사하기 위해 대기 중 1000, 1100, 120$0^{\circ}C$에서 50, 100, 150, 200시간 등온실험(Isothermal oxidation)을 실시하였고, XRD, SEM/EDS, EPMA를 이용하여 생성된 산화막과 코팅 시편의 조직 변화를 조사하였다. 산화온도와 산화시간이 증가할수록 산화막의 박리가 많이 발생하였으며, 분석 결과 미세하게 분포된 a-Al$_2$O$_3$ 입자, NiCr$_2$O$_4$스피넬 상, 미세한 Cr$_2$O$_3$가 관찰되었고, 코팅 조성 변화에 따라 형성되는 이들 산화물의 존재비가 달라졌으며, 산화온도가 높아질수록 산화속도가 가속화되었다.

• Korean Journal of Materials Research
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• v.28 no.6
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• pp.324-329
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• 2018

Needle-like NiO protecting layers on NiCrAl alloy foam, used as support for hydrogen production, are introduced through electroplated Ni and subsequent microwave annealing. To improve the stability of the NiCrAl alloy foam, oxygen concentration of microwave annealing to form a needle-like NiO layer with good chemical stability and corrosion resistance is controlled in a range of 20 and 50 %. As the oxygen concentration increases to 50 %, needle-like NiO forms a dense coating layer on the NiCrAl alloy foam; this layer formation can be attributed to accelerated growth of the (200) plane. In addition, the increased oxygen concentration causes increased NiO/Ni ratio of the resultant coating layer on NiCrAl alloy foam due to improved rate of the oxidation reaction. As a result, the introduction of dense needle-like NiO layers formed at 50 % oxygen concentration improves the chemical stability of the NiCrAl alloy foam by protecting the direct electrochemical reaction between the electrolyte and the foam. Thus, needle-like NiO can be proposed as a superb protecting layer to improve the chemical stability of NiCrAl alloy form.

• Korean Journal of Materials Research
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• v.14 no.2
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• pp.110-114
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• 2004

High velocity oxy-fuel sprayed NiCoCrAlY coatings were oxidized between 1000 and $1200^{\circ}C$ in air, and the oxide scales were examined by XRD, SEM/EDS, and EPMA. The unoxidized coatings consisted mainly of ${\gamma}$'$-Ni_3$Al, with some ${\gamma}$-Ni. The major oxide formed on the coatings was $\alpha$ $-Al_2$$O_3$. Additionally, (CoCr$_2$$O_4$, $CoAl_2$$O_4$) spinels and $Al_{5}$ $Y_3$$O_{12}$ coexisted. NiO was not found, despite of high amount of Ni in the coating. Below the oxide layer, internally formed $Al_2$$O_3$ existed.

• Korean Journal of Metals and Materials
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• v.48 no.6
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• pp.506-513
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• 2010

The composite coatings of $(ZrO_2-8Y_2O_3)$/(Ni-22Cr-10Al-1Y) were prepared by the air plasma spraying method. They consisted of (Ni,Cr)-rich regions,$(ZrO_2-Y_2O_3)$-rich regions, and $Al_2O_3$-rich regions that were formed by oxidation of Al from (Ni-22Cr-10Al-1Y) during spraying. The coatings corroded at 800 and $900^{\circ}C$ in NaCl-$Na_2SO_4$ molten salts up to 50 hr. Ni, Cr and Al oxidized to NiO, $Cr_2O_3$ and ${\alpha}-Al_2O_3$, respectively. These oxides and $(ZrO_2-Y_2O_3)$ were dissolved off into the molten salts during hot corrosion, which resulted in the ever-lasting corrosion of the composite coatings. Chromium diffused out from the (Ni,Cr)-rich regions and oxidized to $Cr_2O_3$, which was most frequently found as surface scales. Aluminum retained in the (Ni,Cr)-rich regions were similarly diffused out.