Abstract
Suspension plasma spraying (SPS) has become an interesting method for the production of thermal barrier coatings for gas turbine components. The development of the SPS process has led to structures with segmented vertical cracks or column-like structures that can imitate strain-tolerant air plasma spraying (APS) or electron beam physical vapor deposition (EB-PVD) coatings. Additionally, SPS coatings can have lower thermal conductivity than EB-PVD coatings, while also being easier to produce. The combination of similar or improved properties with a potential for lower production costs makes SPS of great interest to the gas turbine industry. This study compares a number of SPS thermal barrier coatings (TBCs) with vertical cracks or column-like structures with the reference of segmented APS coatings. The primary focus has been on lifetime testing of these new coating systems. Samples were tested in thermo-cyclic fatigue at temperatures of 1100 °C for 1 h cycles. Additional testing was performed to assess thermal shock performance and erosion resistance. Thermal conductivity was also assessed for samples in their as-sprayed state, and the microstructures were investigated using SEM.
Highlights
The development of the gas turbine for propulsion and power generation is pushing the evolution of new materials and processes to allow for greater performance and efficiency [1]
Example microstructures for Type 1 and 2 coatings are displayed for HVOF and air plasma spraying (APS) bond coats in Figures 2 and 3, respectively
The microstructure of the coating a Type 3 (A3) suggests it to be the most porous of the Suspension plasma spraying (SPS) coatings investigated here; it is feasible that a denser SPS coating could have an erosion rate on par with a dense vertically cracked (DVC) coating
Summary
The development of the gas turbine for propulsion and power generation is pushing the evolution of new materials and processes to allow for greater performance and efficiency [1]. APS has the advantage of lower overall cost, higher process flexibility, lower as-sprayed thermal conductivity and long lifetimes [5,6]. APS coatings are highly susceptible to sintering, which degrades the mechanical and thermal properties of the coatings [7,8,9]. The EB-PVD process can produce columnar structures that can tolerate larger amounts of expansion and contraction [10], but these coatings tend to be more thermally conductive than APS coatings. EB-PVD coatings are preferred for smaller critical components in the turbine section that experiences centrifugal loading and the highest levels of thermal shock; while, because of the superior thermal insulation properties, APS is commonly used to coat combustor liners
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
