Affiliation:
1. Center for Engineering Research, Research Institute, King Fahd University of Petroleum and Minerals, P.O. Box 1639, Dhahran 31261, Saudi Arabia
Abstract
Current technology of thermal barrier coating systems used in gas turbine blade applications relies on the use of a metallic bond coat, which has a twofold function: (i) it develops a thin layer of aluminum oxide enhancing the adhesion of the ceramic top coat and (ii) it provides an additional resistance to oxidation. It was the objective of this study to develop an understanding of the role of platinum in bond coats of the diffusion-type deposited on a nickel-based superalloy. Two Pt-containing bond coats were included in the study: (i) a platinum-aluminide and (ii) a bond coat formed by interdiffusion between an electroplated layer of platinum and the superalloy substrate. In both cases, the top ceramic coat was yttria-stabilized zirconia. For reference purposes, a simple aluminide bond coat free of Pt was also included in the study. Thermal exposure tests at 1150°C with a 24 h cycling period at room temperature were used to compare the coating performance. Microstructural features were characterized by various electron-optical techniques. Experimental results indicated that Pt acts as a “cleanser” of the oxide-bond coat interface by decelerating the kinetics of interdiffusion between the bond coat and superalloy substrate. This was found to promote selective oxidation of Al resulting in a purer Al2O3 scale of a slower growth rate increasing its effectiveness as “glue” holding the ceramic top coat to the underlying metallic substrate. However, the exact effect of Pt was found to be a function of the state of its presence within the outermost coating layer. Of the two bond coats studied, a surface layer of Pt-rich gamma prime phase (L12 superlattice) was found to provide longer coating life in comparison with a mixture of PtAl2 and beta phase. This could be related to the effectiveness of gamma prime phase as a sink for titanium minimizing its detrimental effect on the adherence of aluminum oxide.
Subject
Mechanical Engineering,Energy Engineering and Power Technology,Aerospace Engineering,Fuel Technology,Nuclear Energy and Engineering
Reference27 articles.
1. Non-Metallic Materials for Gas Turbine Engines: Are they Real;Sims;Advanced Materials and Processes
2. Physical Vapor Deposition Coatings for Aircraft Turbine Blades;Lammermann;Advanced Materials and Processes
3. Mechanisms Controlling the Durability of Thermal Barrier Coatings;Evans;Prog. Mater. Sci.
4. The Effect of Pre-Oxidation Treatment on the Cyclic Life of EB-PVD Thermal Barrier Coatings With Platinum-Aluminide Bond Coats;Tolpygo;Surf. Coat. Technol.
5. Effect of Pt on the Oxide-to-Metal Adhesion in Thermal Barrier Coating Systems;Tawancy;J. Mater. Sci.
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