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Instrumented tensile adhesion tests on plasma sprayed thermal barrier coatings

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Journal of Materials Engineering

Abstract

Tensile adhesion tests (TATs) which are normally utilized for industrial quality control procedures have been used for research purposes to examine failure mechanisms of plasma sprayed coatings. This work is applied to two layer coatings (NiCrAlY or NiCrAlZr bond coat with a yttria stabilized zirconia ceramic overlay) which are tested in tension perpendicular to the surface. The mechanical behavior of the bond coat and ceramic overlay were not measured separately. However, the specific component of the coating which sustains the major deformation is related to the failure locus and enables an empirical determination of the bond coat and ceramic overlay deformations to be postulated.

It has been determined that adhesive failure within the bond coat exhibits greater failure strain than cohesive failure of the ceramic overlay. This view lends support to the commonly accepted understanding of these intermediate coatings being highly compliant. The absolute extension exhibited by failures which occur only through the ceramic coating (i.e., cohesive failure) is greater than that of adhesive failure because the ceramic coating is much thicker than the bond coat.

The stress vs. extension data can be expressed in terms of stress vs. strain, and hence the modulus of the coating components approximated to be about 100 MPa. This value is several orders in magnitude lower than that previously reported in the literature and the technical reasons for this discrepency are discussed.

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Authors and Affiliations

  1. Department of Materials Engineering, Monash University, 3168, Clayton, Victoria, Australia

    Christopher C. Berndt

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  1. Christopher C. Berndt
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Berndt, C.C. Instrumented tensile adhesion tests on plasma sprayed thermal barrier coatings. J. Mater Eng. 11, 275–282 (1989). https://doi.org/10.1007/BF02834137

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