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A comparative study of microstructure and lifetime of Thermal Barrier Coatings obtained by Suspension Plasma Spray and Plasma Spray - Physical Vapor Deposition
University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
2020 (English)Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesisAlternative title
En jämförande studie av mikrostrukur och livslängd för termiska barriärbeläggningar producerade genom Suspension Plasma Spray och Plasma Sprayed Physical Vapor Deposition (Swedish)
Abstract [en]

Thermal barrier coatings (TBCs) play a crucial role in modern gas turbine engines used in aero-engines, and power generation to protect the underlying metal substrate from high working temperatures by facilitating a temperature gradient. TBC is a bilayer material system consisting of a ceramic topcoat layer and a metallic bondcoat layer. The ceramic topcoat is transparent to oxygen as well as exhaust gas at high temperatures, as a result, a slow growing aluminium oxide film known as the thermally grown oxide layer is formed from an alumina enriched composition of bondcoat. The two most widely used methods to deposit ceramic topcoats are atmospheric plasma spray (APS) and electron beam-physical vapor deposition (EB-PVD). Topcoats deposited by the APS typically have a lamellar structure with the presence of globular pores, on the other hand, the topcoat in EB-PVD processed TBCs have a strain tolerant columnar structure. EB-PVD processed columnar microstructured TBCs exhibit high in-plane strain tolerance because of which they are of much interest. However, the EB-PVD process is very expensive. Suspension plasma spray (SPS) and Plasma spray- physical vapor deposition (PS-PVD) are the emerging processes that are relatively cheaper and also, are able produce strain resistant columnar microstructure. It is important to note that many factors determine the survival of thermal barrier coatings in harsh working environments. This study aims to understand how different micro-structural features of the topcoat and different bondcoat spray processes can affect the per-formance of the thermal barrier coatings. The bondcoats were sprayed using high velocity air fuel and vacuum plasma spray processes. Thermal barrier coatings with various topcoats, dense and porous, sprayed using atmospheric plasma spray, suspension plasma spray and plasma spray- physical vapor deposition were analysed. Plasma spray- physical vapor deposition was found the have highest thermal cyclic lifetime among all the thermal barrier coatings studied in this work. High velocity air fuel processed bondcoat exhibited better oxidation resistance than vacuum plasma spray processed bondcoats resulting in a uniform passivating thermally grown oxide layer.

Place, publisher, year, edition, pages
2020. , p. 27
Keywords [en]
Suspension Plasma Spraying; Plasma Spray- Physical Vapor Deposition; Thermal Barrier Coatings; Bondcoat Topography; Thermal Cyclic Fatigue (TCF)
National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:hv:diva-15900Local ID: EXM902OAI: oai:DiVA.org:hv-15900DiVA, id: diva2:1470979
Subject / course
Mechanical engineering
Educational program
Masterprogram i tillverkningsteknik
Supervisors
Examiners
Available from: 2020-10-19 Created: 2020-09-27 Last updated: 2020-10-19Bibliographically approved

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