Formation of TiN-Al2O3-ZrO2 Composite Coatings by Gas Tunnel Type Plasma Spraying

Abstract

Abstract High performance Thermal Barrier Coating (TBC) has been expected for use under extream conditions in advanced industrial fields. A high performance of zirconia (ZrO2) composit coating was achieved by gas tunnel type plasma spraying. The zirconia-alumina (ZrO2-Al2O3) 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 ZrO2-Al2O3 composite coating was clarified to make TiN-Al2O3 -ZrO2 Composite Coatings. The TiN coating was overcoated on the ZrO2-Al2O3 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-Al2O3 -ZrO2 Composite Coatings by Gas Tunnel Type Plasma Spraying. In addition, the performance of TiN thick composite coating was discussed as a heat resistant TBC.