• Proceedings of the KWS Conference
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• 2003.05a
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• pp.111-113
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• 2003

The existing heating unit is indirect-heating method that make use or the nichrome wire or halogen lamp. The indirect-heating method has the demerits of long warming time, high power consumption and many organization parts. In this study, the heating unit of direct-heating method manufactured as being the thermal spray coating of conductive heating material on the surface of heating unit in order to improve the demerits of indirect-heating method. And YSZ added Ni-20Cr that had moderate electrical resistivity was chosen of the conductive heating material.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.11a
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• pp.57-59
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• 2001

• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.396-403
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• 2011

In this study, we investigated the mechanical behaviors of layered thermal barrier coatings by indentations. Various single and double-layered thermal barrier coatings were deposited by air plasma spray process using different type of commercialized YSZ (Yttria stabilized zirconia) starting powders. Indentation stress-strain curve, load-displacement curve and hardness of the single and the double-layered thermal barrier coatings were obtained experimentally and analyzed. The indentation damages at the same loads were compared, and thus, the results depend on the structure of each coating. The result indicates improvement in damage resistances from tailoring of layered structures in the component of gas turbine system is expected.

• Journal of the Korean Ceramic Society
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• v.54 no.6
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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.

• Journal of the Korean Ceramic Society
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• v.55 no.2
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• pp.178-184
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• 2018

In the present study, $TiB_2-Co$ composite coatings were thermally sprayed onto the surface of a 304 stainless steel substrate using an atmospheric plasma spray (APS). The phase analysis of the powders and plasma-sprayed coatings was performed using X-ray diffractometry analysis. The microstructures of the coatings were studied by a scanning electron microscope (SEM). The average particle size and flowability of the feedstocks were also measured. Both $TiB_2-32Co$ and $TiB_2-45Co$ (wt.%) coatings possessed typical dense lamellar structures and high-quality adhesion to the substrate. The oxidation behaviors of the coatings were studied at $900^{\circ}C$ in an atmospheric environment. In addition, the cross-sectional images of the oxidized coatings were analyzed by SEM. A thin and well-adhered layer was formed on the surface of both $TiB_2-Co$ coatings, confirming satisfactory high-temperature oxidation resistance. The kinetic curves corresponding to the isothermal oxidation of the coatings illustrated a short transient stage from rapid to slow oxidation during the early portion of the oxidation experiment.

• Journal of the Korean institute of surface engineering
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• v.31 no.1
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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.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.694-696
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• 2011

The high enthalpy plasma research center in Chonbuk national university is under construction for four types of plasma equipments. The equipments are 1set of 0.4 MW class enhanced Huels type plasma equipment, 1 set of 2.4 MW class enhanced Huels type plasma quipment, 1 set of 60 kW RF plasma equipment and 1 set of 200 kW RF plasma equipment. 60kW RF plasma system is R&D and pilot scale production equipment of nano powder synthesis and plasma spray coating. 200kW RF plasma system is mass production equipment with high power capacity of nano powder synthesis. 0.4MW plasma system can be applied to the ground test facility for material testing under re-entry conditions for space vehicles.

• Journal of Welding and Joining
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• v.18 no.5
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• pp.112-116
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• 2000

The development of new spraying processes has increased the demand for high quality protective coatings. Many thermal spraying processes have been developed to obtain coatings for a wide spectrum of materials and substrates. The plasma spray process was used to deposit coatings of WC-12%Co powders on mild steel substrate, and the characteristics of as-sprayed and vacuum heat treated coatings have been investigated. The variations of microhardness and bond strength in WC-12%Co coatings after heat treatment under vacuum circumstance have been investigated. The effects of phases and morphologies of WC-12%Co coatings have been investigated by utilizing X-ray diffraction and scanning electron microscopy, respectively. The microhardness and bond strength of the coatings were increased with increasing the temperature in the temperature range of $700^{circ}C~1000^{\circ}C$. The bond strength was obtained 49 MPa after vacuum heat treatment at $1000^{\circ}C$.

• Tribology and Lubricants
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• v.18 no.4
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• pp.305-311
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• 2002

Three different kinds of brake discs including two coated brake discs and one steel disc were tested under the same experimental conditions on a reduced scale braking test bench. A braking test bench was specially designed to analyse thermo-mechanical and frictional behaviors of two types of brake with different sizes in stop and hold braking modes. Plasma spray coating technique was also used to coat the discs with ceramic powder. During the test four commercial brake pads were coupled with discs. Ceramic coated discs showed good stability in friction coefficient at high speed and high energy braking conditions. But they caused large wear loss of pad mass compared with the steel disc. It was shown that thermal barrier effect in ceramic coated discs adjusted the thermal partition between pad and disc. For a steel disc. it showed fluctuating friction coefficient at high speed but small wear loss of pad mass compared with ceramic coated discs.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.429-430
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• 2002

In this study, three kinds of brake: discs including two coated brake discs and one steel disc were tested under the same experimental conditions on a reduced scale braking test bench. Plasma spray coating technique was used to coat ceramic powder on the discs. In the test, four commercial sintered brake pads were coupled with discs. Ceramic coated discs have shown good stability in friction coefficient at high speed and high energy braking conditions. However, ceramic coated discs caused more wear loss of pad mass than the steel disc. It was shown that thermal barrier effect in ceramic coated discs adjusted the thermal partition between pad and disc. Steel disc showed fluctuating friction coefficient at high speed but less wear loss of pad mass than ceramic coated discs.