• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2012.05a
• /
• pp.346-346
• /
• 2012

탄소 탄소 복합재료(C/C Composites)는 모재의 성분이 탄소로 구성되어 있어 약 $500^{\circ}C$이상의 산화분위기에서는 쉽게 산화되는 결점을 가지고 있다. 본 연구에서는 내산화성을 향상시키기 위한 방법으로서 Plasma Spray 코팅방법을 사용하여 다층 코팅막을 형성시킨 후 $1500^{\circ}C$에서 10시간동안 산화시험을 하였다.

• Journal of the Korean institute of surface engineering
• /
• v.50 no.5
• /
• pp.366-372
• /
• 2017

Plasma electrolytic oxidation(PEO) has attracted attention as a surface treatment which has high wear resistance and corrosion resistance. PEO is generally considered as cost-effective, environmentally friendly and superior in terms of coating performance. Most of studies about the PEO processes have been applied to light metals such as Al and Mg. Because the strength of Al and Mg is weaker than that of steel, there is a limit to the application. In this study, PEO process was used to form oxide coatings on Hot dipped aluminized(HDA) steel and the characteristics of the coating film according to the PEO current density were studied. The morphology was observed by SEM and component was analyzed by using EDS. The corrosion behaviors of PEO coating films were estimated by exposing salt spray test at 5 wt.% NaCl solution and measuring polarization curves in deaerated 3 wt.% NaCl solution. With the increase of PEO process current density, the pore size of the coating surface and the thickness of coating increased. It was confirmed that no Fe component was present on the coating surface. PEO coating films obviously showed good corrosion resistance compared with HDA. It is considered that the PEO coating acts as a barrier to protect the base material from external factors causing corrosion.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2007.11a
• /
• pp.15.2-15.2
• /
• 2007

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2005.11a
• /
• pp.181-182
• /
• 2005

• Journal of the Korean institute of surface engineering
• /
• v.49 no.6
• /
• pp.595-603
• /
• 2016

Rare-earth zirconates, including lanthanum zirconate and gadolinium zirconate, have been investigated as ones of the most promising candidates for next-generation thermal barrier coating (TBC) materials due to their excellent properties such as low thermal conductivity, chemical stability at high temperature and so on. In this study, TBCs with three compositions, in the $La_2O_3-Gd_2O_3-ZrO_2$ system with reduced rare-earth contents from $RE_2Zr_2O_7$ compositions, were fabricated by using suspension plasma spray with different suspension preparation methods. The phase formation, microstructure, and thermal properties of TBCs were examined. In particular, each coating exhibited single fluorite phase and a dense, vertically-separated microstructure. The potential of coatings with rare-earth zirconates for TBC applications was also discussed.

• Korean Journal of Metals and Materials
• /
• v.46 no.6
• /
• pp.363-369
• /
• 2008

Effects of top coat morphology and thickness on thermal fatigue behavior of thermal barrier coatings (TBC) were investigated in this study. Thermal fatigue tests were conducted on three coating specimens with different top coat morphology and thickness, and then the test data were compared via microstructures, cycles to failure, and fracture surfaces. In the air plasma spray specimens (APS1, APS2), top coat were 200 and $300{\mu}m$ respectively. The thickness of top coat was about $700{\mu}m$ in the perpendicular cracked specimen (PCS). Under thermal fatigue condition at $1,100^{\circ}C$, the cycles to top coat failure of APS1, APS2, and PCS were 350, 560 and 480 cycles, respectively. The cracks were initiated at the interface of top coat and thermally grown oxide (TGO) and propagated into TGO or top coat as the number of thermal fatigue cycles increased. For the PCS specimen, additive cracks were initiated and propagated at the starting points of perpendicular cracks in the top coat. Also, the thickness of TGO and the decrease of aluminium concentration in bond coat do not affect the cycles to failure.

• Korean Journal of Materials Research
• /
• v.24 no.2
• /
• pp.116-122
• /
• 2014

$Bi_2Sr_2CaCu_2O_x$(Bi-2212) and $Bi_2Sr_2Ca_2Cu_3O_y$(Bi-2223) high-Tc superconductors(HTS) have been manufactured by plasma spraying, partial melt process(PMP) and annealing treatment(AT). A Bi-2212/2223 HTS coating layer was synthesized through the peritectic reaction between a 0212 oxide coating layer and 2001 oxide coating layer by the PMP-AT process. The 2212 HTS layer consists of whiskers grown in the diffusion direction. The Bi-2223 phase and secondary phase in the Bi-2212 layer were observed. The secondary phase was distributed uniformly over the whole layer. As annealing time goes on, the Bi-2212 phase decreases with mis-orientation and irregular shape, but the Bi-2223 phase increases because a new Bi-2223 phase is formed inside the pre-existing Bi-2212 crystals, and because of the nucleation of a Bi-2223 phase at the edge of Bi-2212 crystals by diffusion of Ca and Cu-O bilayers. In this study the spray coated layer showed superconducting transitions with an onset Tc of about both 115 K, and 50 K. There were two steps. Step 1 at 115 K is due to the diamagnetism of the Bi-2223 phase and step 2 at 50 K is due to the diamagnetism of the Bi-2212 phase.

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.11a
• /
• pp.187-190
• /
• 2009

$LaCrO_3$ series are the most common candidate materials for a ceramic interconnect for SOFC and the thermal expansion coefficient of these matches very well with that of YSZ electrolyte. In this study, characteristics of the coated films on the anode-support, which were formed by using $La_{0.8}Ca_{0.2}CrO_3$, $La_{0.8}Sr_{0.2}CrO_3$, $La_{0.8}Ca_{0.2}Co_{0.1}Cr_{0.9}O_3$ for ceramic interconnet for SOFC, were investigated. All powders showed single perovskite phase and the precursors had spherical shapes of $2{\mu}m{\sim}30{\mu}m$. According to SEM analysis, coated film of LCC on pretreated anode-support was more thicker, whereas the coated film on untreated anode-support was densely formed. As the results of electrical conductivity of anode-support coated with the ceramic interconnects, LCCC exhibited the most excellent electrical conductivity of 0.15S/cm at $750^{\circ}C$.

• Composites Research
• /
• v.30 no.2
• /
• pp.84-93
• /
• 2017

This study investigates thermal and mechanical characterization of environmental barrier coating on the $SiC_f-SiC$ composites. The spherical environmental barrier coating (EBC) powders are prepared using a spray drying process for flowing easily during coating process. The powders consisting of mullite and 12 wt% of Ytterbium silicate are air plasma sprayed on the Si bondcoat on the LSI SiC fiber reinforced SiC composite substrate for protecting the composites from oxidation and water vapor reaction. We vary the process parameter of spray distance during air plasma spray of powders, 100, 120 and 140 mm. After that, we performed the thermal durability tests by thermal annealing test at $1100^{\circ}C$ for 100hr and thermal shock test from $1200^{\circ}C$ for 3000 cycles. As a result, the interface delamination of EBC never occur during thermal durability tests while stable cracks are prominent on the coating layer. The crack density and crack length depend on the spray distance during coating. The post indentation test indicates thermal tests influence on the indentation load-displacement mechanical behavior.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.20 no.10
• /
• pp.3234-3242
• /
• 1996

This paper describes experimental results of modified small punch( MSP) test conducted to evaluate the fracure characteristics and mechanical properties of plasma sparayed zirconia ($ZrO_2$ stabilized with 8wt. % $Y_20_3$ : YSZ) NiCrAlY composite. The mixing ratios of YSZ/NiCrAlY were 0/100, 25/75, 50/50, 100/0 v.%. Test temperatures ranged from 293K to 1473K. This study is directed at development of thermal barrrier coating(TBC) system with superior heat resistance and mechanical properties. The microstructure and fracture process of the composite were examined by SEM and AE method. The mechanical properties of 100% YSZ were nearly independent of the temperatures tested in this study. In contrast, the NiCrAlY-containing composites showed a significant decrease of the mechanical properties above 1273K, showing a ductile- brittle transition behavior up to the temperature. Furthermore, it can seen that 25% YSZ/75% NiCrAlY composite gave the highest fracure strength and fracture energy among the mixing ratio tested over the temperature range.