|JECH David||Brno University of Technology|
|Spoluautoři ČELKO Ladislav, CHRÁSKA Tomáš, KLAKURKOVÁ Lenka, DUBSKÝ Jiří, ŠVEJCAR Jiří|
Eutectic ceramic Al2O3-ZrO2-SiO2 also termed Eucor (as a top coat) and CoNiCrAlY (as bond coat) coatings were sprayed onto the surface of newly developed fine-grained cast polycrystalline nickel-based superalloy Inconel 713 LC by means of water stabilized plasma (WSP) and atmospheric plasma spraying (APS) respectively. One half of as-sprayed samples was annealed at the temperature of 950 °C for 10 hours and followed separately isothermal heat treatment of all samples at 1050 °C for 10, 50, 100, 200 and 500 hours in ambient atmosphere. Influence of shot-time and long-time isothermal exposure on interactions at bond coat/top coat interface were studied. It was found that uniform and continuous oxide layer also termed thermally grown oxide (TGO) formed and grew in thickness across the bond coat/top coat interface in case of all samples with and without heat treatment. Relationship between dwell time, heat treatment and growth in thickness of TGO was also found. Delamination of ceramic top coat in the region near to the top coat/TGO interface was evocated by stresses initiating in Eucor top coat due to its shrinkage during cooling. Microstructural changes at top coat/bond coat interface were investigated by means of scanning electron microscope with an energy dispersive microanalyzer and image analysis techniques.