Title

Phase Distribution In, And Origin Of, Interfacial Protrusions In Ni-Cr-Al-Y/Zro2 Thermal Barrier Coatings

Keywords

Interfaces; Microstructure; Oxidation; Thermal barrier coatings (TBCs); Thermal cycling; Transmission electron microscopy (TEM)

Abstract

Interfacial morphology and reaction products in thermal barrier coating systems were investigated by scanning and transmission electron microscopy (SEM and TEM). The samples consist of yttria-stabilized zirconia (YSZ; 6-8 wt.% yttria) deposited by air plasma spraying onto either of two types of bond coats: a layer consisting of Ni-15.9Cr-5.3Al-0.6Y with 5 wt.% of alumina particulate added, or one that was only the base Ni-Cr-Al-Y composition. In samples thermally cycled to failure in a burner rig, numerous interfacial protrusions of several microns or more in size are observed. These have a complex microstructure and contain elemental Ni intermixed with Ni(Al,Cr)2O4 spinel, (Al,Cr)2O3, and other oxides. Unlike some prior studies, nickel oxide (NiO) was not detected. Protrusion microstructures were similar for the two bond coat systems, but interfacial protrusions for the case of the base composition (i.e. no added alumina particulate) did not contain any spinel phase. Comparison of cross-sectional samples before and after oxidation indicates that the protrusions arise from the encapsulation of isolated segments of the bond coat. The intermixing of metallic Ni grains with oxides in the reaction zone may contribute to failure by affecting local stresses during thermal cycling. © 2002 Elsevier Science B.V. All rights reserved.

Publication Date

9-1-2002

Publication Title

Materials Science and Engineering A

Volume

334

Issue

1-2

Number of Pages

65-72

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1016/S0921-5093(01)01795-6

Socpus ID

0036721005 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/0036721005

This document is currently not available here.

Share

COinS