Ultrasonic technique for measuring porosity of plasma-sprayed alumina coatings |
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Authors: | S Parthasarathi B R Tittmann E J Onesto |
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Affiliation: | (1) Concurrent Technologies Corporation, 15904 Johnstown, PA, USA;(2) Present address: Western Digital Corporation, 95054 Santa Clara, CA, USA;(3) Pennsylvania State University, 16802 University Park, PA, USA |
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Abstract: | Porosity is an important factor in plasma-sprayed coatings, especially ceramic coatings. Excessive poros-ity can adversely
affect the performance of the coated component in various ways. An ultrasonic nonde-structive measurement technique has been
developed to measure porosity in plasma-sprayed alumina coatings. The technique is generic and can be extended to other ceramic
coating systems. To test the tech-nique, freestanding alumina coatings with varying levels of porosity were fabricated via
plasma spray. Samples with varying porosity, obtained through innovative fabrication techniques, were used to gener-ate a
calibration curve. The ultrasonic velocity in the low-frequency range was found to be dependent on the density of freestanding
coatings (measured via Archimedian techniques). This dependence is the basis of the development of a technique to measure
the density of coatings. |
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Keywords: | alumina nondestructive testing porosity ultrasonic velocity |
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