Study On Preparation And Thermal Shock Performance Of NiCrAlY-ZrO₂ Thermal Barrier Coatings

NiCrAlY-ZrO₂ thermal barrier coatings are widely employed in the thermal protective field of high-temperature components of aircraft engine due to their good insulation, wear and corrosion resistance properties. There are many ways to prepare thermal barrier coatings, while using the combination of elecron spark deposition?ESD? and microarc oxidation is a relatively new method. Good metallurgical bonding can be obtained between the base and coatings by ESD which is easy operation. An in-situ grown ceramic layer is fabricated on the metal surface by micro-arc oxidation process, which combined strongly with the metal. Therefore, this research mainly explores the feasibility of preparing NiCrAlY-ZrO₂ coatings using ESD and microarc oxidation compound technology and the thermal shock properties of the coatings.Firstly, two kinds of NiCrAlY coatings of different Al content were prepared on the surface of GH4169 by ESD method. The best NiCrAlY coating was chosen as bond coat according to deposition law, the microstructures and properties, phase composition and cross-sectional hardness of the deposition layer. Results showed that two deposition layers had similar morphology, uneven. NiCrAlY coating with high Al content reached its deposition limitation of approximately 17 times under the voltage of 100 V. The thickness could be increased by annealing again, but it could not continue to increase after a few cycles. In contrast, the coating with low Al content could sustain thickening and did not reach its limited thickness. The properties of the coating which was prepared under the voltage of 100 V was better than 50 and 150 V.Secondly, Zr coating was deposited on the surface of sample which had coated the optimal NiCrAlY bond coat by EDS, and the deposition law, the morphology were researched. The results showed that the deposition law of Zr coating was that the increased thickness was 31 ?m when unit area weight gain was 0.01 g/cm², and the deposition limitation was approximately 79 times.Then microarc oxidation method was used on the samples which had been deposited Zr coating at constant voltage model, and the influence of oxidation times on ZrO₂ ceramic coating structures was studied, the regulation of oxidation time and thickness variation was revealed. The results showed that the surface roughness was gradually increased and cracks began to appear with the prolonging oxidation time in the constant voltage mode. The thickness of oxide film increased with the increasing oxidation time, while the oxidation rate is contrary.Finally, the thermal shock resistance of completely oxidation samples was tested under 750, 850, 950 ?, and the influence of the thermal shock temperature on thermal shock resistance of ZrO₂ ceramic coatings was researched. The results showed that the thermal shock life of the coating was different at different temperatures. The higher the thermal shock temperature was, the shorter the thermal fatigue life of the coating was. Thermal shock times were 51, 32, 19 times, when the thermal shock temperature were 750, 850, 950 ?, which also proved that the NiCrAlY-ZrO₂ thermal barrier coating using ESD and microarc oxidation process had certain thermal shock resistance.