METHOD FOR MANUFACTURE OF HIGH TEMPERATURE CYLINDRICAL COMPONENT FOR A GAS TURBINE ENGINE

Abstract

A method for the manufacture of a cylindrical component suited to use in a high temperature environment and incorporating an erosion resistant coating (4) on its outer cylindrical surface (6) is described. The method comprises, in sequential steps; providing a work piece (1) having a cylindrical body including a pair of axially spaced radially extending ribs (3a, 3b) defining an annular trough (2) therebetween. Shot peening the work piece (1). Applying an erosion resistant coating (4) in the annular trough (2) to a depth which sits radially inwardly of the radially outermost ends of the ribs (3a, 3b). Turning the radially outermost ends of the ribs (3a, 3b) whereby to match the depth of the coating (4) and provide an outer cylindrical surface with a consistent diameter across both ribs (3a, 3b) and the coating (4).

Claims

1. A method for the manufacture of a cylindrical component suited to use in a high temperature environment and incorporating an erosion resistant coating on its outer cylindrical surface, the method comprising, in sequential steps; providing a work piece having a cylindrical body including a pair of axially spaced radially extending ribs defining an annular trough therebetween, shot peening the work piece, applying an erosion resistant coating in the annular trough to a depth which sits radially inwardly of the radially outermost ends of the ribs, turning the radially outermost ends of the ribs whereby to match the depth of the coating and provide an outer cylindrical surface with a consistent diameter across both ribs and the coating.

2. A method as claimed in claim 1 wherein, the cylindrical component is configured to serve as a drum of a compressor of a gas turbine engine.

3. A method as claimed in claim 1 wherein the work piece comprises a drum made from a plurality of disc forgings welded together.

4. A method as claimed in claim 3 wherein the trough extends across one or more welded joints.

5. A method as claimed in claim 1 wherein the erosion resistant coating is applied using a thermal spraying process.

6. A method as claimed in claim 1 wherein the work piece comprises a high temperature alloy which is a nickel based alloy or a titanium based alloy.

7. A method as claimed in claim 1 wherein the coating is a multi-layered coating.

8. A method as claimed in claim 7 wherein the coating comprises a first layer of an erosion resistant coating and a top layer of a thermally insulating material.

9. A method as claimed in claim 1 wherein the erosion resistant coating is a self-bonding coating.

10. A method as claimed in claim 1 wherein the erosion resistant coating comprises particles of a mechanically clad, chemically clad or gas atomised combination of Nickel and Aluminium.

11. A method as claimed in claim 10 wherein the Nickel component of the erosion resistant coating comprises 80% or greater.

12. A method as claimed in claim 11 wherein the Nickel component comprises from 90% to 96%.

13. A method as claimed in claim 8 wherein the top layer comprises a ceramic material.

14. A method as claimed in claim 13 wherein the ceramic comprises an Yttria stabilised Zirconia (YSZ).

15. A method as claimed in claim 14 wherein the YSZ comprises 90% or greater of Zircona.

16. A method as claimed in claim 15 wherein the YSZ comprises 91-93% Zirconia and up to 9% Yttria.

17. A method as claimed in claim 8 wherein the top layer is provided from a powder and deposited using a thermal spraying process.

18. A method as claimed in claim 17 wherein the erosion resistant coating comprises particles of a mechanically clad, chemically clad or gas atomised combination of Nickel and Aluminium.

19. A method as claimed in claim 9 wherein the coating comprises a first layer of an erosion resistant coating and a top layer of a thermally insulating material which is provided from a powder and deposited using a thermal spraying process.

20. A method for manufacturing a gas turbine engine including the steps of providing one or more components which are susceptible to erosion by means of the method of claim 1 and assembling these with other components into the gas turbine engine.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0014] An embodiment of the method of the invention is now described with reference to the accompanying drawings in which;

[0015] FIG. 1 shows in cross section, one half of a compressor drum for use in a gas turbine engine as is known from the prior art;

[0016] FIG. 2 shows sequential steps of a prior known method for the manufacture of the compressor drum of FIG. 1;

[0017] FIG. 3 shows sequential steps of a method of manufacture according to an embodiment of the invention;

[0018] FIG. 4 shows a section of a gas turbine engine into which cylindrical components made in accordance with the invention might be incorporated.

[0019] FIGS. 1 and 2 have been described above. Novel aspects of the method of the invention can be understood by referencing FIG. 3 with FIG. 2.

DETAILED DESCRIPTION OF DRAWINGS AND SOME EMBODIMENTS

[0020] In step a) of FIG. 3 the drum 1 is formed from two disc forgings welded at weld 5 (though the drum need be welded from two components). The welded drum has a circumferentially outer surface 6 and circumferentially inner surface 7. Ribs 3a and 3b which may be machined from the welded forgings define the trough 2. In step b) the drum is shot peened on all surfaces to generate compressive stresses in the outer surface to discourage the propagation of cracks from within the forging or weld. In step c) an erosion resistant coating is applied in the trough, for example using a plasma spraying technique. The coating is applied to a depth which is a depth d less than the radially outermost surfaces of the ribs 3a, 3b. In step d), with the coating in place, the protruding depth d of the ribs 3a, 3b is removed in a turning operation by a lathe tool 8.

[0021] It will be appreciated that in the method of the invention, the coating is not succumbed to a shot peening operation. This permits the use of coatings which might be damaged by a shot peening operation. For example, the method allows for a range of top coats to be provided, for example to provide thermal barrier or chemical corrosion protection to the erosion resistant coating. Such coatings (which are often ceramic and brittle) can be easily damaged by shot peening. More generally, the method may reduce the number of machining operations needed to finish the component. Since turning is commonly used to machine features such as spigots around the circumference, the levelling of the ribs with the coating can be achieved as a continuation of the turning operation removing the need for a separate grinding operation. Consumable costs for the manufacture can thereby be reduced. Improved dimensional control is also achievable with a turning versus a grinding operation when the turning operation is performed in a single step with the machining of engine datums such as the spigot of the component.

[0022] Whilst the embodiment describes a drum for a compressor, the method also has application in the manufacture of other turbine engine components, for example in gear boxes and pumps.

[0023] FIG. 4 shows a gas turbine engine into which components made in accordance with the invention might be incorporated.

[0024] With reference to FIG. 4, a gas turbine engine is generally indicated at 40, having a principal and rotational axis 41. The engine 40 comprises, in axial flow series, an air intake 42, a propulsive fan 43, a high-pressure compressor 44, combustion equipment 45, a high-pressure turbine 46, a low-pressure turbine 47 and an exhaust nozzle 48. A nacelle 50 generally surrounds the engine 40 and defines the intake 42.

[0025] The gas turbine engine 40 works in the conventional manner so that air entering the intake 42 is accelerated by the fan 43 to produce two air flows: a first air flow into the high-pressure compressor 44 and a second air flow which passes through a bypass duct 51 to provide propulsive thrust. The high-pressure compressor 44 compresses the air flow directed into it before delivering that air to the combustion equipment 45.

[0026] In the combustion equipment 45 the air flow is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive the high and low-pressure turbines 46, 47 before being exhausted through the nozzle 48 to provide additional propulsive thrust. The high 46 and low 47 pressure turbines drive respectively the high pressure compressor 44 and the fan 43, each by suitable interconnecting shaft.

[0027] For example, the drum of compressor 44 may be manufactured in accordance with the method of the invention.

[0028] Other gas turbine engines to which the present disclosure may be applied may have alternative configurations. By way of example such engines may have an alternative number of interconnecting shafts (e.g. three) and/or an alternative number of compressors and/or turbines. Further the engine may comprise a gearbox provided in the drive train from a turbine to a compressor and/or fan.

[0029] It will be understood that the invention is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the scope of the invention as described in the appended claims. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.