Abstract
The bond coat plays an important role in the failure of the thermal barrier coating (TBC) system used for gas turbines [1,2]. In this research, the CoNiCrAlY coated Ni-base superalloy specimens were used for developing evaluation method for interfacial damage in the coat. Samples were exposed at 1000°C and 1100°C for up to 1000 hours. The morphology and residual stress in the thermally grown oxide (TGO) layer on the CoNiCrAlY coating were characterized by microscopic observation and luminescence spectroscope, respectively. The microstructure and damage o\n both the coating surfaces and the cross sections were observed by optical microscope and scanning electron microscope. According to the results, the low pressure plasma sprayed CoNiCrAlY coating (LPPS) showed the thinnest TGO layer and lowest residual stress.Residual stress decreased with an increase in exposure time, depending on the morphology of TGO layer. The effects of thermal spraying methods on the oxidation of yttrium in TGO layer and BC layer and its influence on interfacial damage were discussed.
Highlights
Increasing the inlet temperature of gas turbines is the main way to increase their efficiency
We investigated the morphology and the residual stresses of the specimens after thermal exposure to verify the relationship between the oxidation behavior of the thermally grown oxide (TGO) and the interfacial damage of the thermal barrier coating (TBC)
TGO formed on the bond coat after thermal exposure
Summary
Increasing the inlet temperature of gas turbines is the main way to increase their efficiency. The thermal barrier coatings (TBCs) on high temperature alloys can increase the heat resistance for 100-300°C. The thermally grown oxide (TGO) appears between the TC and the BC. We investigated the morphology and the residual stresses of the specimens after thermal exposure to verify the relationship between the oxidation behavior of the TGO and the interfacial damage of the TBC.
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