Initiation and growth of delamination cracks in vacuum plasma sprayed thermal barrier coatings
2004 (English)In: Surface Engineering 2004: Proceedings of the 3rd International Surface Engineering Congress (ASM International), 2004, 284-290 p.Conference paper (Refereed)
Thermal barrier coatings are widely used in air-borne and land-based gas turbines. In these applications they serve as thermal insulators in hot components (burner cans/liners, turbine vanes and turbine blades). The present paper is aimed to describe the failure mechanism of a vacuum plasma sprayed thin thermal barrier coating system. Also the coating degradation mechanism (delamination followed by spallation) in terms of interfacial crack growth data is investigated and presented. In the present paper a 200 µm thick NiCrAlY bond coat was chosen together with a 350µm thick 7wt% yttria stabilised zirconia top coat. The coating system was exposed to thermal cyclic fatigue with a thermal cycle ranging from 100 °C to 1100 °C and a cycle time of 70 minutes. After thermal cyclic testing all specimen were subjected to standard sample preparation routines and inspected by optical microscopy and scanning electron microscopy. In order to describe interfacial crack growth an interface damage measure is used. For the present coating system under current thermal load conditions a mainly black interface fracture is discovered. The top coat exhibit microcrack formation after thermal fatigue, but these cracks do not contribute to the final fracture appearance. Crack growth rates are compared to local stress intensity levels at the top coat / bond coat interface. From crack length measurements are crack growth data da/dN = f(ΔKeff) calculated.
Place, publisher, year, edition, pages
2004. 284-290 p.
thermal barrier coating, crack growth, delamination, interface, NiCrAlY
Engineering and Technology
IdentifiersURN: urn:nbn:se:liu:diva-22779Local ID: 2110ISBN: 0871708191ISBN: 978-0871708199OAI: oai:DiVA.org:liu-22779DiVA: diva2:243092
3rd International Surface Engineering Conference, Orlando FL, August 2-4 2004