Abstract No.:
5194

 Scheduled at:
Thursday, June 08, 2017, Hall 12 12:20 PM
Aviation & Power Generation Industry II


 Title:
On the formation of dense vertically cracked yttria stabilized zirconia coatings: An investigation to relate the particle and deposition states with stress-microstructure characteristics

 Authors:
Ramachandran Chidambaram Seshadri / State University of New York at Stony Brook, USA
Gopal Dwivedi/ Center for Thermal Spray Research, Stony Brook University, NY
Gregory Smith*/ Stony Brook University, USA
Sanjay Sampath/ Center for Thermal Spray Research, Stony Brook University, NY

 Abstract:
The dense vertically cracked (DVC) thermal barrier coatings (TBC) are highly strain tolerant and favourable for application in hot section components of aircraft as well as stationary gas turbines. The initiation, propagation, spacing and dimensions of vertical cracks during the deposition of Yttria Stabilized Zirconia (YSZ) DVC coatings are influenced mainly by the stresses generated during coating deposition. The particle state parameters (plasma power, gas flow rates, injection angle, spray distance and powder feed rate) and the deposition state parameters (application rate, spray bead over-lap and substrate: material, cooling techniques, surface treatments etc.,) govern the nature of stresses generated in the coating during deposition. In this investigation, a fine grade YSZ powder was deposited on stainless steel substrates using a cascaded arc air plasma spray (APS) torch under different particle and deposition states. The stresses generated (termed evolving stress) during the deposition of the coatings were calculated using the change in curvature of the substrate measured using an in-situ coating property (ICP) sensor. A variety of DVC morphologies namely narrow, wide, isolated, heavily segmented and horizontally branched deposits were obtained under the considered experimental conditions. The mechanisms for formation of such an assortment of DVC TBCs were proposed based on ICP results.

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