Methods and apparatus for coating gas turbine engines

#This invention relates generally to gas turbine engines, and more particularly to methods and apparatus for fabricating a coating for gas turbine engine blades.

#At least some known gas turbine engines include one or more turbine rotors, which include a rotor disk and a plurality of circumferentially-spaced rotor blades, sometimes referred to as blades. Known blades typically include an airfoil, a platform, a shank, and a dovetail. Each dovetail is received within a slot or opening defined in the rotor disk to secure the blades to the rotor disk. The airfoils extend from the disk into the flow of combustion gases within the engine and convert kinetic energy of the gas flow into rotational mechanical energy.

#Fouling and surface degradation generally occur when as the result of burning fuels containing alkali metals that combine with sulfur during the combustion process and deposit low melting salts on the surface of the parts. Additional contaminants may come from air ingested and/or water injected for NOx control or power augmentation.

#FIG. 1 is a cross-sectional schematic illustration of an exemplary gas turbine engine.

#FIG. 2 is a perspective view of an exemplary rotor blade that may be used with a gas turbine engine, for example the gas turbine engine shown in FIG. 1.

#FIG. 3 is a side view of a portion of an exemplary rotor blade including a first coating, a second coating, a third coating, and a fourth coating that may be used with the gas turbine engine shown in FIG. 1.

#FIG. 1 is a schematic illustration of an exemplary gas turbine engine 10. In the exemplary embodiment, gas turbine engine 10 includes a compressor 12, a turbine 14, a turbine 16, and a combustor 18. Compressor 12 and turbine 14 are coupled together by a rotor shaft 20. In the exemplary embodiment, turbine 16 is coupled to an external load, such as, but not limited to, a generator (not shown) or a propeller (not shown) via a shaft 22. In some embodiments, engine 10 is a gas turbine engine commercially available from General Electric Company, Greenville, S.C. In operation, air flows through compressor 12 and compressed air is supplied to combustor 18, wherein the compressed air is mixed with a fuel and ignited to produce combustion gases. Combustion gases channeled from combustor 18 drive turbines 14 and 16, which drive rotation of respective shafts 20 and 22 about a longitudinal axis 24 for respectively powering compressor 12 and the external load.

#FIG. 2 is a perspective view of an exemplary rotor blade 26 that may be used with a gas turbine engine, for example gas turbine engine 10 (shown in FIG. 1). A rotor assembly, for example turbine 14 (shown in FIG. 1), may include a plurality of rotor blades 26, oriented such that each rotor blade 26 is coupled to a rotor disk (not shown in FIG. 2) that is coupled to a rotor shaft, for example shaft 20 (shown in FIG. 1) and such that blades 26 are spaced about a circumference of the rotor disk. Each rotor blade 26 includes an airfoil 28, a platform 30, a shank 32, and a dovetail 34. Airfoil 28, platform 30, shank 32, and dovetail 34 are sometimes collectively referred to as a bucket. In an alternative embodiment, blade 26 includes a tip cap.

#Each airfoil 28 includes opposite sidewalls 36 and 38. Sidewall 36 is convex and defines a suction side of airfoil 28, and sidewall 38 is concave and defines a pressure side of airfoil 28. Sidewalls 36 and 38 are joined together at a leading edge 40 and at an axially-spaced trailing edge 42 of airfoil 28: More specifically, airfoil trailing edge 42 is spaced chord-wise and downstream from airfoil leading edge 40. Sidewalls 36 and 38 each extend longitudinally or radially outward in span from a blade root 44 positioned adjacent platform 30, to an airfoil tip 46.