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5539 |
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Thursday, June 08, 2017, Hall 28 2:40 PM Equipment / Consumables & Powders, Wires, Suspensions II |
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Design, development and characterization of advanced TBC powders and coatings |
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Andrea Scrivani / H.C. Starck GmbH, Germany Carlo Gualco / Ansaldo Energia, Italy Alessandra Bonadei/ Ansaldo Energia, Italy B. Gallo*/ Ansaldo Energia, Italy |
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For several years the main used material for TBC coatings has been the so-called 8YSZ (a partially stabilized ZrO2 with 7 to 9wt% Y2O3). This material can be deposited by EB-PVD or by plasma spray processes. The requested coating characteristics have changed in the past years in function of the development of the most advanced gas turbines, where higher efficiency is obtained by the increasing of gas inlet temperature. Also the utilization method of the turbine has changed passing from a base load service to a peak service, with a lot of switch on and off, which make also the industrial gas turbines similar in the service to the aeronautical engines. Therefore the development of the TBC coating has regarded the coating characteristics and in particular the porosity, the presence of predetermined vertical cracks and the increasing of the coating thickness. All this development has been applied to material with the standard above mentioned chemical composition. But in the same time the research has looked to new compositions with different yttria content as well as different substances such as the rare earths, in order to reduce the thermal conductivity of the coating and therefore to grant a better insulation to the substrate material. Several OEMs or institutes have developed their own patented material for this purpose. This paper reviews the current status of the TBC coating material development and presents the results related to the development of a new low K TBC material, which has been deposited and fully characterized from the chemical and physical point of view as well as from the service performance point of view with isothermal oxidation, cyclic oxidation and corrosion resistance determination. |