A Study in the High Temperature Tribological Characteristics of the Plasma Sprayed ZrO2 Coating

Abstract

Abstract The Thermal Barrier Coating (TBC) used to improve the heat barrier and wear resistant property in high temperature of the aircraft engine and the automobile engine, usually has a two layer structure. One is a ceramic top layer for heat insulation and the other is a metal bond layer to facilitate the bond strength between the top ceramic layer and the substrate. But, the coated layers can be peeled off because of the accumulation of the thermal stress by the difference of the thermal expansion coefficient between metal and ceramics in a heat cyclic environment. In this study, the intermediate layer produced by plasma spray process was introduced to reduce the thermal stress. The powders of plasma spray coating were Yttria Stabilized Zirconia (YSZ), Magnesia Stabilized Zirconia (MSZ) and NiCrAIY. The intermediate layer was sprayed with the powders of partially stabilized zirconia with 50wt% NiCrAIY between the ceramics top coat and the bond coat for the purpose of alleviating heat expansion. The high temperature wear and thermal shock test were conducted. The high temperature wear resistance of the YSZ TBC was better than that of the MSZ TBC. The wear resistance decreased with increasing temperature between 400°C to 600°C. The 3 layers TBC with YSZ top coating showed the best thermal shock resistance. This means that the intermediate layer played an important roll to alleviate the difference of the thermal expansion between metallic layer and ceramics layer. SEM and OM were examined. The bond strength, hardness test, and wear test were also studied.