Influence of plasma spray parameters on mechanical properties of yttria stabilized zirconia coatings. II: Acoustic emission response

Yttria (8 wt.%) stabilized zirconia (YSZ) with a NiCrAlY bond coat was atmo spherically plasma sprayed on mild steel substrates using various processin g parameters including YSZ coating thickness, bond coat thickness, stand of f distance, and substrate temperature. The cracking behavior of these coati ngs under four point bending load was examined using an acoustic emission ( AE) recorder. The numbers of AE events exhibited during the elastic and pla stic deformation of coatings were analyzed. Using multi-linear regression a nalysis, the number of AE events was correlated to the spray parameters. Th is analysis revealed that coatings with thicker YSZ top coat and NiCrYAl bo nd coat sprayed on a heated substrate at shorter stand off distance exhibit ed more AE activity and released higher AE energy under the bending. The gr eater emission activity and higher AE energy were evidence of severe cracki ng. (C) 2000 Elsevier Science S.A. All rights reserved.