Development and Assessment of Coatings for Future Power Generation Turbines (original) (raw)

Thermo-Mechanical Characterizations of Coatings for HP Turbines

Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education, 1998

Three different coatings were studied in this work : vacuum plasma-sprayed NiCoCrAlYTa, electrolytically deposited NiCoCrAlYTa and Ni-Pt aluminide diffusion coatings. These three coatings were deposited on AM3 single crystal alloy, lit tensile properties of coated single crystal test specimens wae investigated. Ductile to Brittle Transition Temperatures (DM) were determined from tensile tests. All the coatings wae examined before and after testing. All the tested coatings induce a ductile/brittle transition. Strain rate has a great influence on the transition temperature. The comparison between plasma-sprayed deposition aid electrodeposition illustrates the strong influence of coating microstructure. In every case, NiCoCrAlYTa coatings were more ductile, and then less detrimental, than aluminide coatings.

Bonding mechanisms in the application of thermal barrier coatings to turbine blades

2004

Thermal barrier coatings (TBC's) are used to protect gas turbine blades from environmental degradation as well as to increase thermodynamic efficiency. Most TBC systems consist of a ceramic thermal barrier coating such as partially stabilized zirconia adhering to an oxidation resistant bond coat, which in turn is bonded to the turbine blade. This is required since partially stabilised zirconia will not readily bond to superalloys. However, the TBC can fail in service either by bond coat oxidation or thermal expansion mismatch between the bond coat and the TBC. A systematic literature survey has shown that the superalloy substrate material, type of bond coat selected, with the coating application techniques i.e. thermal spray or Electron Beam PVD (EBPVD) plays a fundamental role in determining the failure mechanisms involved. This program of work is concerned with the development of coatings with enhanced temperature capabilities for turbine blade applications by understanding th...

HIGH TEMPERATURE COATINGS FOR INDUSTRIAL GAS TURBINE USERS

High temperature coatings are used for protecting the high temperature turbine components from environmental attack due to oxidation and hot corrosion. These coatings have developed from sim ple aluminide coatings to complex overlay and duplex coatings. Over the past 15 years thermal barr ier coatings, which lower the temperature of the metal, have become increasingly used in industrial gas turbines.

Wear Characteristics of Superalloy and Hardface Coatings in Gas Turbine Applications-A Review

MDPI, 2020

In the gas-turbine research field, superalloys are some of the most widely used materials as they offer excellent strength, particularly at extreme temperatures. Vital components such as combustion liners, transition pieces, blades, and vanes, which are often severely affected by wear, have been identified. These critical components are exposed to very high temperatures (ranging from 570 to 1300 • C) in hot-gas-path systems and are generally subjected to heavy repair processes for maintenance works. Major degradation such as abrasive wear and fretting fatigue wear are predominant mechanisms in combustion liners and transition pieces during start-stop or peaking operation, resulting in high cost if inadequately protected. Another type of wear-like erosion is also prominent in turbine blades and vanes. Nimonic 263, Hastelloy X, and GTD 111 are examples of superalloys used in the gas-turbine industry. This review covers the development of hardface coatings used to protect the surfaces of components from wear and erosion. The application of hardface coatings helps reduce friction and wear, which can increase the lifespan of materials. Moreover, chromium carbide and Stellite 6 hardface coatings are widely used for hot-section components in gas turbines because they offer excellent resistance against wear and erosion. The effectiveness of these coatings to mitigate wear and increase the performance is further investigated. We also discuss in detail the current developments in combining these coating with other hard particles to improve wear resistance. The principles of this coating development can be extended to other high-temperature applications in the power-generation industry.

Thermal Barrier Coatings for Gas-Turbine Engine Applications

Science, 2002

Hundreds of different types of coatings are used to protect a variety of structural engineering materials from corrosion, wear, and erosion, and to provide lubrication and thermal insulation. Of all these, thermal barrier coatings (TBCs) have the most complex structure and must operate in the most demanding high-temperature environment of aircraft and industrial gas-turbine engines. TBCs, which comprise metal and ceramic multilayers, insulate turbine and combustor engine components from the hot gas stream, and improve the durability and energy efficiency of these engines. Improvements in TBCs will require a better understanding of the complex changes in their structure and properties that occur under operating conditions that lead to their failure. The structure, properties, and failure mechanisms of TBCs are herein reviewed, together with a discussion of current limitations and future opportunities.

Processing and Advancements in the Development of Thermal Barrier Coatings: A Review

Coatings

Thermal barrier coating is critical for thermal insulation technology, making the underlying base metal capable of operating at a melting temperature of 1150 °C. By increasing the temperature of incoming gases, engineers can improve the thermal and mechanical performance of gas turbine blades and the piston cylinder arrangement. Recent developments in the field of thermal barrier coatings (TBCs) have made this material suitable for use in a variety of fields, including the aerospace and diesel engine industries. Changes in the turbine blade microstructure brought on by its operating environment determine how long and reliable it will be. In addition, the effectiveness of multi-layer, composite and functionally graded coatings depends heavily on the deposition procedures used to create them. This research aims to clarify the connection between workplace conditions, coating morphology and application methods. This article presents a high-level overview of the many coating processes an...

The Evolution of Thermal Barrier Coatings in Gas Turbine Engine Applications

Journal of Engineering for Gas Turbines and Power, 1994

Thermal barrier coatings (TBCs) have been used for almost three decades to extend the life of combustors and augmentors and, more recently, stationary turbine components. Plasma-sprayed yttria-stabilized zirconia TBC currently is bill-of-material on many commercial jet engine parts. A more durable electron beam-physical vapor deposited (EB-PVD) ceramic coating recently has been developed for more demanding rotating as well as stationary turbine components. This ceramic EB-PVD is bill-of-material on turbine blades and vanes in current high thrust engine models and is being considered for newer developmental engines as well. To take maximum advantage of potential TBC benefits, the thermal effect of the TBC ceramic layer must become an integral element of the hot section component design system. To do this with acceptable reliability requires a suitable analytical life prediction model calibrated to engine experience. The latest efforts in thermal barrier coatings are directed toward c...

Lifetime evaluation of a thick thermal barrier coated superalloy used in turbine blade

Materials Science and Engineering: A, 2010

This paper deals with evaluation of lifetime of a thick thermal barrier coated (TBC), AE-437A Ni base superalloy mostly employed for manufacturing compressor and stationary stator blades in aero turbines from accelerated creep tests. Severe high-temperature oxidation is likely the cause of the reduced lifetime of the bare substrate while accelerated creep experiments are carried out in an oxidizing environment. The bond coat was capable of supporting some load and the apparent equivalence of 800 • C stress rupture properties of thickly and thinly coated AE-437A was not anticipated since the thick TBC coating with its 160 m bond coat represents an ∼20% increase in cross-sectional area for a 3 mm × 4 mm sample; whereas thin TBC with a 100 m bond coat has a ∼12% increase in cross-section for the same initial sample size. Delamination of top coat layer and bond coat from the substrate occurred at very high creep stress, whereas delamination of TBC from the bond coat was evident at intermediate creep stress level. It was found that furnace thermal cycling (10-50, 1-h thermal cycles) on the TBC samples prior to creep loading at 70 MPa/800 • C, drastically reduces the lifetime or rupture life of the TBCs. The damage generated by this micro-cracking is expected to be a primary life-limiting factor.