Influence of Isothermal Exposure on Microstructural Changes Resulting in Delamination of Eutectic Al2O3+ZrO2+SiO2 Thermal Barrier Coating

Influence of Isothermal Exposure on Microstructural Changes Resulting in Delamination of Eutectic Al2O3+ZrO2+SiO2 Thermal Barrier Coating

Paper in proceedings (conference paper)

Eutectic ceramic Al2O3-ZrO2-SiO2 also termed Eucor (as a top coat) and CoNiCrAlY (as a bond coat) coatings were sprayed onto the surface of recently developed fine-grained cast polycrystalline nickel-based superalloy Inconel 713 LC by means of water stabilized plasma (WSP) and atmospheric plasma spraying (APS) techniques, respectively. Specimens were subjected to isothermal oxidation at 1050 °C for 10, 50, 100, 200 and 500 hours in ambient atmosphere, prior to which a half of the as-sprayed specimens was annealed at the temperature of 950 °C for 10 hours. Influence of short-time and long-time isothermal exposure on interactions at the bond-coat/top-coat interface was studied. The uniform and continuous oxide layer, also termed the thermally grown oxide (TGO), was formed and grew at the bond-coat/top-coat interface in all samples, both with and without the heat pre-treatment. Relationship between the dwell time, heat treatment and TGO growth kinetics was quantified. Microstructural changes at top-coat/bond-coat interface were investigated by means of a scanning electron microscope equipped with an energy dispersive microanalyzer and by means of image analysis techniques. Delamination of the ceramic top coat in the region near to the top-coat/TGO interface was evocated by stresses initiated in the Eucor top coat due to its shrinkage during cooling.

Eutectic ceramic Al2O3-ZrO2-SiO2 also termed Eucor (as a top coat) and CoNiCrAlY (as a bond coat) coatings were sprayed onto the surface of recently developed fine-grained cast polycrystalline nickel-based superalloy Inconel 713 LC by means of water stabilized plasma (WSP) and atmospheric plasma spraying (APS) techniques, respectively. Specimens were subjected to isothermal oxidation at 1050 °C for 10, 50, 100, 200 and 500 hours in ambient atmosphere, prior to which a half of the as-sprayed specimens was annealed at the temperature of 950 °C for 10 hours. Influence of short-time and long-time isothermal exposure on interactions at the bond-coat/top-coat interface was studied. The uniform and continuous oxide layer, also termed the thermally grown oxide (TGO), was formed and grew at the bond-coat/top-coat interface in all samples, both with and without the heat pre-treatment. Relationship between the dwell time, heat treatment and TGO growth kinetics was quantified. Microstructural changes at top-coat/bond-coat interface were investigated by means of a scanning electron microscope equipped with an energy dispersive microanalyzer and by means of image analysis techniques. Delamination of the ceramic top coat in the region near to the top-coat/TGO interface was evocated by stresses initiated in the Eucor top coat due to its shrinkage during cooling.

Thermal Barrier Coatings, Thermal Plasma Spraying, Heat Treatment, Electron Microscopy – Scanning, Image Analysis

Thermal Barrier Coatings, Thermal Plasma Spraying, Heat Treatment, Electron Microscopy – Scanning, Image Analysis

JECH, D.; ČELKO, L.; CHRÁSKA, T.; SLÁMEČKA, K.; KLAKURKOVÁ, L.; DUBSKÝ, J.; ŠVEJCAR, J.

2016

23.05.2014

TANGER Ltd.

Ostrava

978-80-87294-54-3

Metal 2014

1

885

890

1981

http://hdl.handle.net/