Toward Durable Thermal Barrier Coating with Composite Phases and Low Thermal Conductivity

Abstract

High-efficiency turbine engines highly rely on the further improvement of the novel technologies related to combustion, cooling and thermal barrier coating (TBC) with the increase in inlet temperatures. Thermal barrier coatings with higher thermal stability and lower thermal conductivity (low-k) than current 8YSZ TBC had attracted a lot of academia and industries’ attentions and activities. The present work aimed to focus on exploring a path toward a durable TBC with better thermal durability and low-k capability by overcoming the technical, practical and economic barriers for current low-k TBC development and applications. The concept of composite phase ceramics was proposed for low-k TBC material design, in an effort to combine the desirable attributes of unique phase constitution, low conductivity k, high fracture toughness and good process economy. Further, thermal spray process was optimized for the topcoats of the low-k ceramics by controlling and measuring the effect of key process parameters on porous coating architecture, deposition rate and process efficiency. To evaluate the performance of the low-k TBCs, both an isothermal oxidation test and a thermal cycling test were conducted. The test results of the composite phase ceramics exhibited promising for a durable low-k TBC measured by several desirable property attributes.