Porosity measurement of YSZ ceramic coating deposited with different parameters deposition by different methods of characterization

Ceramic coatings are applied in mechanical components subject to high temperature conditions, normally are deposited by plasma thermal spraying process. In this work, the porosity of YSZ ceramic coatings, deposited with different parameters conditions were analyzed by optical and electron microscopy, ultrasound technique and mercury porosimetry. It was verified that porosity measurement by optical and electron microscopy is very sensitive with respect to metallographic preparation, mainly cutting process, and gray level adjustment. BSE technique showed less scatter results with easier porosity visualization, compared with optical microscopy. The porosity of the coatings was also measured by ultrasound technique and mercury porosimetry, it was observed that the ultrasound velocity increase with porosity reduction. Ultrasound technique showed a good correlation with optical and electronic measurement. However the mercury porosimetry showed a low reliable results because of the low ceramic coating volume, compared to the total sample volume.