Mueller matrix polarimetry on plasma sprayed thermal barrier coatings for porosity measurement

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Date: Dec. 10, 2017
From: Applied Optics(Vol. 56, Issue 35)
Publisher: Optical Society of America
Document Type: Author abstract; Report
Length: 195 words

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Abstract :

Yttria-stabilized zirconia (YSZ) is the most widely used material for thermal plasma sprayed thermal barrier coatings (TBCs) used to protect gas turbine engine parts in demanding operation environments. The superior material properties of YSZ coatings are related to their internal porosity level. By quantifying the porosity level, tighter control on the spraying process can be achieved to produce reliable coatings. Currently, destructive measurement methods are widely used to measure the porosity level. In this paper, we describe a novel nondestructive approach that is applicable to classify the porosity level of plasma sprayed YSZ TBCs via Mueller matrix polarimetry. A rotating retarder Mueller matrix polarimeter was used to measure the polarization properties of the plasma sprayed YSZ coatings with different porosity levels. From these measurements, it was determined that a sampleAEs measured depolarization ratio is dependent on the sampleAEs surface roughness and porosity level. To this end, we correlate the depolarization ratio with the samplesAE surface roughness, as measured by a contact profilometer, as well as the total porosity level, in percentage measured using a micrograph and stereological analysis. With the use of this technique, a full-field and rapid measurement of porosity level can be achieved.

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Gale Document Number: GALE|A525536217