Metallography of Thermal Spray Coatings
Effects of Metallographic Preparation Technique
Photomicrographs of the same poorly plasma sprayed
alumina / 3% titania coating at about X50 magnifgication. This coating
was poorly sprayed by depositing the coating too thickly per pass
generating lamination faults. The metallographic preparation
precedure for each was slightly different. The two photomicrographs on
the left were prepared using fairly typical metallographic techniques
for ferrous materials, showing the effects of "particle pluck out". The
photomicrograph on the right was prepared using special developed
techniques specifically for plasma sprayed alumina ceramic coatings,
showing clearly the crack edges, unmelted particles and a more
realistic view of density.
Photomicrographs of the same plasma sprayed alumina/3%
titania coating at about X250 magnifgication.