Surface laser-glazing of plasma-sprayed thermal barrier coatings

Atmospheric plasma-sprayed (APS) ZrO 2–8%WtY 2O 3 thermal barrier coatings (TBCs) were subjected to a CO 2 continuous wave laser-glazing process in order to generate an external dense layer produced by different processing parameters. For that purpose, different beam scanning speeds and track overla...

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Bibliographic Details
Published in:Applied surface science 2005-07, Vol.247 (1), p.313-319
Main Authors: Batista, C., Portinha, A., Ribeiro, R.M., Teixeira, V., Costa, M.F., Oliveira, C.R.
Format: Article
Language:English
Subjects:
Condensed matter: structure, mechanical and thermal properties
Cross-disciplinary physics: materials science
rheology
Exact sciences and technology
Laser-glazing
Materials science
Physics
Plasma spraying
Solid surfaces and solid-solid interfaces
Surface structure and topography
Surface treatments
Surfaces and interfaces
thin films and whiskers (structure and nonelectronic properties)
Thermal barrier coating
Zirconia
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Summary:Atmospheric plasma-sprayed (APS) ZrO 2–8%WtY 2O 3 thermal barrier coatings (TBCs) were subjected to a CO 2 continuous wave laser-glazing process in order to generate an external dense layer produced by different processing parameters. For that purpose, different beam scanning speeds and track overlapping were chosen. Surface roughness has been reduced significantly after laser-glazing. Despite the surface crack network, all laser-glazed specimens presented a fully dense and porous free external layer with a columnar microstructure. Surface cracks along the densified layer were found to have tendency to be oriented in two perpendicular directions, one in the direction of the laser beam travel, the other perpendicular to it. Moreover, the cracks parallel to the beam moving direction are found to be on the overlapping zone, coinciding with the edge of the subsequent track. The cracks along the densified layer are vertical and tend to branch and deviate from the vertical direction within the porous PS coating. The largest overlapping allied to the smallest amount of irradiated energy generated the most uniform layer with the shortest crack branches within the PS coating. For the as-sprayed coating, the XRD results revealed mainly t′ non-transformable tetragonal zirconia with a small percentage of residual monoclinic zirconia. All glazed coatings presented only t′ non-transformable tetragonal zirconia with some variations on preferable crystal orientation.
ISSN:0169-4332
1873-5584
DOI:10.1016/j.apsusc.2005.01.047