Abstract

The objective of this study was to investigate the effects of thermal spray process selection and corresponding bondcoat surface roughness on thermal barrier coating (TBC) performance. TBC's consisting of a 300 µm (12 mil) thick air plasma sprayed (APS) top coating of ZrO2-8 Wt.% Y2O3 and CoNiCrAlY bondcoats deposited by three different thermal spray processes were produced and their surface roughness characterized. The bondcoats were deposited using low pressure plasma spray (LPPS®), shrouded air plasma spray (SPS) and high velocity oxy-fuel (HVOF) combustion spray. Bondcoat surface profiles were measured by profilometric and interferometric techniques and surface roughness values calculated. TBC performance was evaluated by adhesive bond strength testing, thermal shock and thermal cycling testing, and microstructural analysis. Results showed that the bondcoat deposition process used and corresponding surface roughness had significant effects on the adhesive strength, thermal shock and thermal cycling lifetime, and failure mechanisms.

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