Aluminum Nitride and Silicon Nitride for High Temperature Gas Turbine Engines

High temperature applications demand materials that have a variety of properties such as high strength, toughness, creep resistance, fatigue resistance, as well as resistance to degradation by their interaction with the environment. All potential metallic materials are unstable in many high temperatures environments without the presence of a protective coating on the component surface. High temperature alloys derive their resistance to degradation by forming and maintaining a continuous protective oxide surface layer that is slow-growing, very stable, and adherent. In aggressive environments, the superalloy oxidation and corrosion resistance needs to be augmented by coatings. Propulsion materials for Naval shipboard gas turbine engines are subjected to the corrosive environment of the sea to differing degrees. Increasing fuel efficiency and platform capabilities require higher operating temperatures that may lead to new degradation modes of coatings and materials. Fuel contaminants or the lack of contaminants from alternative synthetic fuels may also strongly influence coating and/or materials performance which, in turn, can adversely affect the life in these propulsion or auxiliary gas turbine engines. This paper will dwell on some past results of materials testing and offer some views on future directions into materials research in high temperature materials in aggressive environments that will lead to new advanced propulsion materials for shipboard applications.

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Computational Modeling of High Temperature Deposition in Gas Turbine Engines with Experimental Validation

51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition ◽

10.2514/6.2013-1112 ◽

2013 ◽

Cited By ~ 2

Author(s):

Michael Lawrence ◽

Brian Casaday ◽

Derek Lageman ◽

Jeffrey Bons ◽

Steven Whitaker

Keyword(s):

High Temperature ◽

Computational Modeling ◽

Gas Turbine ◽

Experimental Validation ◽

Turbine Engines ◽

Gas Turbine Engines ◽

Temperature Deposition

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Evaluation of Alternate High Temperature Coatings to Improve Hot Corrosion Resistance in a Shipboard Environment

Volume 4: Cycle Innovations; Industrial and Cogeneration; Manufacturing Materials and Metallurgy; Marine ◽

10.1115/gt2009-59116 ◽

2009 ◽

Author(s):

David A. Shifler ◽

Dennis M. Russom ◽

Bruce E. Rodman

Keyword(s):

High Temperature ◽

Gas Turbine ◽

Corrosion Fatigue ◽

Hot Corrosion ◽

Turbine Engines ◽

Type I ◽

Gas Turbine Engines ◽

Type Ii ◽

Turbine Engine ◽

Type Ii Hot Corrosion

501-K34 marine gas turbine engines serve as auxiliary power sources for the U.S. Navy’s DDG-51 Class. It is desired that 501-K34 marine gas turbine engines have a mean time between removal of 20K hours. While some engines have approached this goal, others have fallen significantly short. A primary reason for this shortfall is hot corrosion (Type I and Type II) damage in the turbine area (more specifically the first row turbine hardware) due to both intrusion of salts from the marine air and from sulfur in the gas turbine combustion fuel. The Navy’s technical community recognizes that engine corrosion problems are complex in nature and are often tied to the design of the overall system. For this reason, two working groups were formed. One group focuses on the overall ship system design and operation, including the inlet and fuel systems. The second, the corrosion issues working group, will review the design and performance of the turbine itself and develop sound, practical, economical, and executable changes to engine design that will make it more robust and durable in the shipboard operating environment. Metallographic examination of unfailed blades removed from a marine gas turbine engine with 18000 operating hours showed that the coating thickness under the platform and in the curved area of transition between the platform to the blade stem was either very thin, or in a few cases, non-existent on each unfailed blade. Type II hot corrosion was evident at these locations under the platform. It was also observed that this corrosion under the platform led to corrosion fatigue cracking of first stage turbine blades due to poor coating quality (high porosity and variable thickness). Corrosion fatigue cracks initiated at several hot corrosion sites and had advanced through the stems to varying degrees. Cracking in a few blades had advanced to the point that would have led to premature blade failure. Low velocity, atmospheric-pressure burner-rig (LVBR) tests were conducted for 1000 hours to evaluate several alternative high-temperature coatings in both Type I and Type II hot corrosion environments. The objectives of this paper are to: (1) report the results of the hot corrosion performance of alternative high temperature coating systems for under the platform of the 1st stage blade of 501-K34 gas turbine engine, (2) compare the performance of these alternative coating systems to the current baseline 1st stage blade coating, and (3) down select the best performing coating systems (in terms of their LVBR hot corrosion and thermal cycling resistance) to implement on future 501-K34 first stage blades for the Fleet.

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