Influence of bond coat surface roughness on the structure of axial suspension plasma spray thermal barrier coatings — Thermal and lifetime performance

• Published in: Surface & coatings technology 2015-04, Vol.268 (April), p.15-23
• Main Authors: Curry, Nicholas, Tang, Zhaolin, Markocsan, Nicolaie, Nylén, Per
• Format: Article
• Language: English
• Subjects: Coating; Coatings; Columns (process); Columns (structural); Manufacturing and materials engineering; Plasma spraying; Produktions- och materialteknik; Sprayers; Sprays; Suspension plasma spray; Thermal barrier coatings; Thermal conductivity; Thermal shock; Thermo-cyclic fatigue; Topography
• ISSN: 0257-8972; 1879-3347; 1879-3347
• DOI: 10.1016/j.surfcoat.2014.08.067

Suspension plasma spraying has become a very promising candidate for the production of strain tolerant coatings for the gas turbine industry. Under certain process conditions suspension plasma spraying (SPS) generates column-like structures in the produced coatings. While a mechanism for column formation has been suggested previously based on columns forming on surface asperities, the effect of modification of surface structures on SPS coating properties has not been investigated. In this study, the surface topography of bond coats within a TBC system were modified by the combination of polishing and surface grit blasting. Yttria stabilized zirconia coatings were deposited using an axial feed suspension plasma spray gun. The surface topography of the resultant coatings was characterized using striped light projection. Samples were tested for thermo-cyclic fatigue lifetime at 1100°C during 1hour cycles. Thermal shock performance was evaluated using the burner rig test and thermal conductivity evaluated using the laser flash analysis. The results indicate that columnar SPS coating microstructure is strongly influenced by surface topography. Test results suggest that control of surface topography may be an important factor to improve the performance of SPS coatings. •Production of columnar SPS thermal barrier coatings is demonstrated.•SPS column size is shown to be influenced by surface topography.•SPS TBC coatings are able to be produced on relatively smooth substrates.•Thermal shock performance of SPS coatings is demonstrated to be high.•Results present a possible route for further coating microstructure improvement.