Metal glass has excellent functions such as high toughness and corrosion resistance. Therefore it is one of the most attractive materials, and many researchers have conducted various developmental research works. However, the metal glass material is expensive and the composite material is preferred for the industrial application. Thermal spraying method is one of potential candidates to produce those metal glass composites. The gas tunnel type plasma system, which has high energy density and efficiency, is useful for smart plasma processing to obtain high quality ceramic coatings such as alumina (Al 2 O 3 ) and zirconia (ZrO 2 ) coatings. In this study, the Fe-base metal glass coatings were produced by the gas tunnel type plasma spraying, and the microstructure and mechanical property were investigated. The Fe-base metal glass coatings of 100µm in thickness were formed densely with Vickers hardness of Hv =1000 at plasma current of 300A.

A crystalline hydroxyapatite (HA) coating was deposited using gas tunnel type plasma spraying at different spraying distances. In this study, the microstructure, adhesion and microhardness of the resulting coatings were investigated to clarify the effect of the spraying distance on the features of sprayed coatings. The results showed that the spraying distance greatly affects the microhardness, adhesion, and crystallinity of the sprayed HA coatings. Microhardness value was increased as the spraying distance was decreased, mainly due to the formation of dense coating with lower porosity. Adhesion was increased, as the spraying distance was decreased due to a good mechanical bonding between the first apatite layer and the substrate. X-ray diffraction patterns of HA coatings showed the formation of high crystalline apatite coating at short spraying distance.

In this paper, composite thermal barrier coatings (TBCs) of Al 2 O 3 +ZrO 2 are deposited on SS304 stainless steel substrates by gas tunnel type plasma spraying. The resultant coating samples prepared with different Al 2 O 3 +ZrO 2 mixing ratio and thickness are compared in corrosion resistance. A potentiostatic anodic polarization corrosion tester is used to get the corrosion characteristics of coated samples to measure their corrosion resistance. From the polarization curves, corrosion potential and deactivated corrosion current density are obtained and analyzed corresponding to the microstructure of the coatings. The results show that the higher alumina content and thicker coatings, the better the corrosion resistance, which is attributed to the diffusion resistance of coating layers to corrosion reaction. The coating microstructure is characterized using an optical microscope imaging system and measured the coating thickness and porosity. The coating porosity and thickness are believed to be the important factors for the variation on the corrosion behavior of Al 2 O 3 +ZrO 2 coated SS304 stainless steel substrates.

High performance Thermal Barrier Coating (TBC) has been expected for use under extream conditions in advanced industrial fields. A high performance of zirconia (ZrO 2 ) composit coating was achieved by gas tunnel type plasma spraying. The zirconia-alumina (ZrO 2 -Al 2 O 3 ) composite coating has a high hardness layer at the surface side of the coating, which shows the graded functionality of hardness, and is expected to use as a Thermal Barrier Coating (TBC). TiN thick coatings which has excellent properties have also been formed at high deposition rate by means of the gas tunnel type plasma reactive spraying. In this study, the fundamental characteristics of this method were investigated by measuring the properties of the titanium nitride (TiN) coatings formed on traversed stainless steel substrate. Some coating characteristics of TiN which depend on the spraying distance, the environmental gas, traverse number etc. were then clarified. The functionally graded property of the ZrO 2 -Al 2 O 3 composite coating was clarified to make TiN-Al 2 O 3 -ZrO 2 Composite Coatings. The TiN coating was overcoated on the ZrO 2 -Al 2 O 3 coating, in order to enhance the performance of such high hardness composite coating. The Vickers hardness of the TiN layer was increased at the coating surface, which corresponded to the result that the coating surface became dense. The graded functionality of the hardness in the thickness direction was increased remarkably in the TiN-Al 2 O 3 -ZrO 2 Composite Coatings by Gas Tunnel Type Plasma Spraying. In addition, the performance of TiN thick composite coating was discussed as a heat resistant TBC.

The one problem of zirconia (ZrO 2 ) coatings is control of the porosity, because the functionality of wear resistance, corrosion resistance, and so on are required for their application in the extreme environment. In this study, a high hardness and dense ZrO 2 coatings is formed by a gas tunnel type plasma spraying under the condition of a short spraying distance. The properties of this ZrO 2 coating formed are investigated about coating qualities, such as Vickers hardness characteristics, wear characteristic, etc. The graded functionality of this coating is clarified by the coating qualities.

The gas tunnel type plasma spraying enables to produce high quality ceramic coatings. Moreover a high hardness coating was obtained at a short spraying distance in the case of alumina coating. A high hardness zirconia (ZrO 2 ) coating could also be obtained at an atmospheric pressure by using the gas tunnel type plasma spraying. The Vickers hardness of the ZrO 2 coating at a short spraying distance was very high: a high hardness of more than Hv = 1200 was achieved at the surface side of the coating. In this study, the characteristics of these high hardness zirconia coatings produced the gas tunnel type plasma spraying were investigated by the measurement of the Vickers hardness of the coating. The microstructure of the obtained high hardness zirconia coatings were also investigated by the microscopic method and by the X-ray diffraction method.