Factors influencing the performance of zirconia based thermal barrier coatings

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Abscheidung kolumnarer Wärmedämmschichten mittels Suspensionsplasmaspritzen (SPS) und Plasma Spray

In dieser Arbeit werden Wärmedämmschichten mittels Suspensionsplasmaspritzverfahren (SPS) und Plasma Spray-Physical Vapor Deposition (PS-PVD) hergestellt, um die Schichtlebensdauer zu verlängern. Zur Erreichung dieses Ziels wird eine oxiddispersionsverstärkte (ODS) Schicht auf den Bondcoat aufgetragen, die den thermischen Ausdehnungskoeffizienten zwischen Bondcoat und Topcoat angleicht und Spannungen reduziert. In einem zweiten Ansatz werden Bondcoats voroxidiert. Die Voroxidation des Bondcoats geht mit der Bildung einer thermisch gewachsenen Oxidschicht einher, die das Schädigungsverhalten der Wärmedämmschicht verändert. Beide Vorgehensweisen verlängern die Lebensdauer der Wärmedämmschicht beim thermischen Zyklieren um ein Vielfaches. Durch Evaluation der Material-, Plasmagas- und Prozessparameter kann die Temperaturwechselbeständigkeit weiter erhöht werden. Die Forschung erfolgte im Rahmen des Sonderforschungsbereichs Transregio 103 "Vom Atom zur Turbinenschaufel".In this work, thermal barrier coatings are produced using Suspension Plasma Spraying (SPS) and Plasma Spray-Physical Vapor Deposition (PS-PVD) processes to extend the coating lifetime. To achieve this goal, an oxide dispersion-strengthened (ODS) layer is applied to the bond coat, aligning the thermal expansion coefficient between the bond coat and top coat and reducing stress. Pre-oxidation of the bond coat accompanies the formation of a thermally grown oxide layer, altering the damage behavior of the thermal barrier coating. Both approaches significantly extend the lifespan of the thermal barrier coating. By evaluating material and process parameters and optimizing plasma gas parameters, the resistance to thermal cycling can be further enhanced. This research was conducted as part of the Collaborative Research Center Transregio 103 "From Atoms to Turbine Blades"

Preparation of Highly Durable Columnar Suspension Plasma Spray (SPS) Coatings by Pre-Oxidation of the CoNiCrAlY Bondcoat

Columnar structured thermal barrier coatings (TBCs) have been intensively investigated due to their potential to enhance the durability and reliability of gas turbine engine components. These coatings consist of vertically aligned columns that provide excellent resistance to thermal cycling. In this study, the lifetime of columnar suspension-plasma-sprayed (SPS) TBCs was evaluated using burner rig tests. The tests were carried out under high-temperature conditions. Significantly, the pre-oxidation of the bondcoat during diffusion bonding treatment was found to have a substantial impact on the performance of the SPS TBCs. The optimized treatment resulted in columnar SPS TBCs demonstrating excellent thermal stability and resistance under the test conditions. The lifetime of the coatings was significantly extended compared to conventional TBCs by pre-oxidation of the CoNiCrAlY bondcoat in argon, which suggests that columnar SPS TBCs have great potential for use in gas turbine engines