The Influence Of Chemical Nickel Plating On QT-500Substrate To Thermal Shock Resistance Of8YSZ Thermal Barrier Coating

Thermal barrier coatings (TBCs) are widely used to improve the efficiency ofaircraft engines and advanced gas turbines. Thermal barrier coating has beenextensively employed to improve the efficiency of advanced gas turbines. Because oftheir low thermal conductivity and good chemical stability, TBC performs theimportant role in protecting heated parts, such as turbine blades and increasing theoperation temperature. TBC can be used to protect the hot section of Low HeatRejection Engine.In this work， TBC which consisted of a NiCoCrAlY bond coat and aZrO2-8wt.%Y2O3top coat，was fabricated on the QT-500cast iron. Electroless nickelplating，which has excellent physical and chemical properties，is widely used inengineering. The purpose of this study is to investigate the influence of electrolessflating to thermal shock resistance of8YSZ thermal barrier coating on QT-500substrate. In this experiment, the Ni-P interlayer was prepared on QT-500substrate,and several processes, including air plasma spray (APS) and high velocity oxygenfuel spray (HVOF) technologies, were used to deposit the TBC. The properties ofTBC were evaluated by thermal cycling tests. High-temperature anti-oxidationbehavior、element diffusion and thermal cyclic failure in TBC were studied by XRDand SEM equipped with EDS.The research showed that the service life of common TBCs was about1000cycles. The TBC spallation was found at the edge of specimen after1000cycles whilethe TBC with interlayer was intact after1400cycles. An oxidation zone mainlyconsisting of Fe and Si oxide was located at the surface of substrate without interlayer.By contrast, for the TBCs with Ni-P interlayer, double-layer oxide layer was found atthe bond coat/interlayer interface and interlayer/substrate interface after the Ni-Pinterlayer failed. The element inter diffusion phenomena was found occurring on bothsides of the Ni-P interlayer during thermal shock test, which improvs the interfacialbonding strength and thermal shock resistance of the TBC. A dense Ni-P interlayercan prevent further diffusion of oxygen and further oxidation of substrate in theprocess of thermal cycling.Generally speaking, the method of employing the electroless platings as interlayerbetween TBCs and cast iron substrate is a technical solution of improving the thermalshock resistance of TBCs.