Premium
Microstructure and Heat Transfer Phenomena in Ceramic Thermal Barrier Coatings
Author(s) -
Scardi Paolo,
Leoni Matteo,
Cernuschi Federico,
Figari Angelamaria
Publication year - 2001
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2001.tb00748.x
Subject(s) - materials science , microstructure , thermal diffusivity , composite material , porosity , thermal barrier coating , texture (cosmology) , physical vapor deposition , lamellar structure , ceramic , grain size , deposition (geology) , grain growth , coating , thermodynamics , paleontology , sediment , biology , computer science , physics , image (mathematics) , artificial intelligence
Comparably thick Y 2 O 3 ‐partially‐stabilized ZrO 2 thermal barrier coatings were deposited by two different techniques, air plasma spray (APS) and electron beam physical vapor deposition (EB‐PVD), on the same type of substrate. Microstructure and grain texture, as studied by SEM and XRD, were markedly different. The complex microstructure of the APS coatings, made of curled lamellar grains, was replaced in EB‐PVD coatings by long columnar grains, aligned along the growth axis, with strong grain texture. Average porosity and other average or intrinsic properties, such as density and specific heat, were nearly the same for all studied coatings; phase composition ranged between 0 and 6 wt% of the m phase in a prevalent t ′‐phase matrix. The main difference was in the shape and orientation of porosity with respect to the thermal flux direction, which was responsible for the different thermal diffusivity that was three times higher in EB‐PVD than in APS coatings. An appropriate modeling of the heat diffusion process, including open and closed porosity with orientation and shape factors, could explain the observed diffusivity values.