Thermal cycling damage in pre-oxidized plasma-sprayed MCrAlY plus YSZ thermal barrier coatings: Phenomenon of multiple parallel delamination of the TGO layer.

SLÁMEČKA, K.; JECH, D.; KLAKURKOVÁ, L.; TKACHENKO, S.; REMEŠOVÁ, M.; GEJDOŠ, P.; ČELKO, L. Thermal cycling damage in pre-oxidized plasma-sprayed MCrAlY plus YSZ thermal barrier coatings: Phenomenon of multiple parallel delamination of the TGO layer. Surface and Coatings Technology, 2020, roč. 384, č. 125328, s. 1-13. ISSN: 0257-8972.

Abstract

This paper focuses on thermal cycling failure of pre-oxidized plasma-sprayed thermal barrier coatings (TBCs) with NiCrAlY and NiCoCrAlY bond-coats and yttria-stabilized zirconia (YSZ) top-coats. Pre-oxidation of full NiCrAlY + YSZ and NiCoCrAlY + YSZ TBC systems to the thickness of the thermally grown oxide (TGO) of similar to 3 mu m was carried out mainly to reduce the influence of initial residual stresses related to the plasma spraying process. The NiCoCrAlY coatings were found to be rougher than the NiCrAlY coatings, the arithmetic average roughness S-a being nearly two times higher and the relative surface area R-s being, respectively, similar to 1.8 and similar to 1.5 for the as-sprayed coatings. It was interesting to observe that despite much greater roughness of its bond-coat, the thermal cycling life of NiCoCrAlY + YSZ TBC system was more than a factor of two shorter when cycled at 1050 degrees C and still only comparable when cycled at 1150 degrees C. This resulted from much larger portion of the interface being influenced by repeated delamination of the TGO layer from the bond-coat, which formed multiple parallel alumina fragments of similar thickness. Most likely, the major cause for such behaviour was the higher thermal expansion of the NiCoCrAlY bond-coat and its higher oxidation rate, although the effect of the interfacial geometry certainly cannot be excluded.

@article{BUT164050, author="Karel {Slámečka} and David {Jech} and Lenka {Klakurková} and Serhii {Tkachenko} and Michaela {Remešová} and Pavel {Gejdoš} and Ladislav {Čelko}", title="Thermal cycling damage in pre-oxidized plasma-sprayed MCrAlY plus YSZ thermal barrier coatings: Phenomenon of multiple parallel delamination of the TGO layer", annote="This paper focuses on thermal cycling failure of pre-oxidized plasma-sprayed thermal barrier coatings (TBCs) with NiCrAlY and NiCoCrAlY bond-coats and yttria-stabilized zirconia (YSZ) top-coats. Pre-oxidation of full NiCrAlY + YSZ and NiCoCrAlY + YSZ TBC systems to the thickness of the thermally grown oxide (TGO) of similar to 3 mu m was carried out mainly to reduce the influence of initial residual stresses related to the plasma spraying process. The NiCoCrAlY coatings were found to be rougher than the NiCrAlY coatings, the arithmetic average roughness S-a being nearly two times higher and the relative surface area R-s being, respectively, similar to 1.8 and similar to 1.5 for the as-sprayed coatings. It was interesting to observe that despite much greater roughness of its bond-coat, the thermal cycling life of NiCoCrAlY + YSZ TBC system was more than a factor of two shorter when cycled at 1050 degrees C and still only comparable when cycled at 1150 degrees C. This resulted from much larger portion of the interface being influenced by repeated delamination of the TGO layer from the bond-coat, which formed multiple parallel alumina fragments of similar thickness. Most likely, the major cause for such behaviour was the higher thermal expansion of the NiCoCrAlY bond-coat and its higher oxidation rate, although the effect of the interfacial geometry certainly cannot be excluded.", address="ELSEVIER SCIENCE SA", chapter="164050", doi="10.1016/j.surfcoat.2019.125328", howpublished="online", institution="ELSEVIER SCIENCE SA", number="125328", volume="384", year="2020", month="february", pages="1--13", publisher="ELSEVIER SCIENCE SA", type="journal article in Web of Science" }