This paper evaluates different techniques for measuring bond coat surface roughness, explores the influence of different thermal spray processes on the surface roughness of bond coats, and correlates bond coat surface roughness with spray parameters. The results of an evaluation of various techniques for measuring the surface roughness of the adhesive layer including the influence of the thermal spraying process, the powder size, the travel speed, and the coating thickness on the roughness of the thermal barrier coatings (TBCs) adhesive layers are presented. Light microscopy, a needle-tracking profile stylus, and non-contact interferometry with white light are used to characterize the adhesive layer surfaces. The results show that the measurement technique used had significant effects on some of the measured surface roughness values. Paper includes a German-language 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 ZrO 2 -8 Wt.% Y 2 O 3 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.