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The influence of oxidation on mechanical and fracture behaviour of an air plasma-sprayed NiCoCrAlY bondcoat
KTH, Superseded Departments, Materials Science and Engineering.
2004 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 187, no 1, 113-121 p.Article in journal (Refereed) Published
Abstract [en]

The influence of isothermal oxidation on room-temperature mechanical and fracture behaviour of an air plasma-sprayed Ni-23Co-17Cr12Al-0.5Y bondcoat was investigated by the miniaturised disc bending test (MDBT) technique. Disc specimens were extracted from the bondcoat region of both as-received and oxidised thermal barrier coating (1000 degreesC, 1000 h). Microstructure analysis revealed that the nonoxidised bondcoat consisted mainly of gamma-phase (Ni-structure) and beta-NiAl. After 500 h of oxidation no NiAl remained in the bondcoat, an effect due to internal as well as external oxidation of Al. The former resulted in the formation of an extensive oxide network and the latter in the formation of an oxide scale between the topcoat and the bondcoat. The crack propagation behaviour of the bondcoat, both in non-oxidised and oxidised condition can be characterised as intergranular with stable growth. The crack propagation resistance is substantial due to the lamellar gain (splat) orientation and the extensive intergranular oxide network, acting as crack deflection and crack branching mechanisms. As an effect of oxidation, crack propagation resistance of the bondcoat increases but the strain to crack initiation decreases.

Place, publisher, year, edition, pages
2004. Vol. 187, no 1, 113-121 p.
Keyword [en]
thermal barrier coating, NiCoCrAlY, bondcoat, oxidation, fracture toughness, strength
National Category
Materials Chemistry
URN: urn:nbn:se:kth:diva-40529DOI: 10.1016/j.surfcoat.2003.12.021ISI: 000224020500016ScopusID: 2-s2.0-18244407311OAI: diva2:442598
QC 20110922Available from: 2011-09-22 Created: 2011-09-16 Last updated: 2011-09-22Bibliographically approved

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