Axial suspension plasma spraying: Microstructure effect on coatings performance

Conference Dates

June 24-29, 2018


Axial Suspension Plasma Spraying (ASPS) is a relatively new thermal spaying technique to produce advanced thermal barrier coatings (TBCs). ASPS has shown to be a very promising technique to produce coatings with lower thermal conductivity as well as higher lifetime than the state-of-art TBCs used today. In addition, ASPS has also shown to have a very wide process window which enables the production of variety of microstructures such as highly dense, highly porous, segmented or columnar. However, tailoring the microstructure of these TBCs for enhanced durability is challenging due to their inherently wide pore size distribution (ranging from few nanometers up to few tens of micrometers).

This work aims to study the effect of feedstock and plasma spray conditions on the various microstructural features and thereby to study the effect of microstructure on coatings functional performance. Various thermo-mechanical properties including thermal conductivity, hardness, E-modulus and toughness along with TBCs lifetime including both the thermal shock as well as thermal cyclic fatigue and sintering behavior is investigated. The effect of various pore sizes at different length scale on various coating properties as well as performance was of specific interest. Based on the detailed experimental investigation conducted in this work, various factors needed for designing an optimized columnar TBC for gas turbine application are discussed. This study reveals that along with the suspension viscosity and surface tension, ceramic top coat total porosity and pore-size distribution at different length scale was found to play varying roles in influencing the TBC performance and were found to be crucial in designing the optimized TBC.

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