Increased Reliability of Gas Turbine Components by Robust Coatings Manufacturing
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Increased Reliability of Gas Turbine Components by Robust Coatings Manufacturing A. Sharma1 • T. Dudykevych1 • D. Sansom1 • R. Subramanian2
Submitted: 13 January 2017 / in revised form: 27 April 2017 Ó ASM International 2017
Abstract The expanding operational windows of the advanced gas turbine components demand increasing performance capability from protective coating systems. This demand has led to the development of novel multi-functional, multi-materials coating system architectures over the last years. In addition, the increasing dependency of components exposed to extreme environment on protective coatings results in more severe penalties, in case of a coating system failure. This emphasizes that reliability and consistency of protective coating systems are equally important to their superior performance. By means of examples, this paper describes the effects of scatter in the material properties resulting from manufacturing variations on coating life predictions. A strong foundation in process-property-performance correlations as well as regular monitoring and control of the coating process is essential for robust and well-controlled coating process. Proprietary and/or commercially available diagnostic tools can help in achieving these goals, but their usage in industrial setting is still limited. Various key contributors to process variability are briefly discussed along with the limitations of existing process and product control methods. Other aspects that are important for product reliability and consistency in serial manufacturing as well as advanced testing methodologies to simplify and enhance product inspection and improve objectivity are briefly described. Keywords advanced testing methodologies gas turbine coatings process control reliability thermal spray coatings & A. Sharma [email protected] 1
Siemens Energy Inc., Charlotte, NC, USA
2
Siemens Energy Inc., Orlando, FL, USA
Introduction The increasing global energy requirements and environmental regulations require increasing power and efficiency of the gas turbine engines and reduced emissions. Increasing efficiency and reducing emissions of gas turbine engines are largely achieved by increasing the firing temperature and reducing cooling air and leakage losses. Even the most advanced metallic systems cannot operate at these temperatures. Therefore, coatings have become an integral part of many IGT materials systems, contributing several key functions such as thermal and oxidation protection, and clearance control. A typical thermal barrier coating (TBC) system consists of a metallic (MCrAlY) bond-coat and ceramic (8YSZ) top coat layer. Increasing temperature capability requirements in GT engines have led to the development of several new TBC systems including new compositions for ceramic top coat and bond-coat and innovative coating architectures. The advancements in ceramic topcoat include use of increased amount of yttria, use of other rare earths (REs), combinations of multiple REs, other dopants/stabilizers,
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