Electricity: measuring and testing – Magnetic – With means to create magnetic field to test material
Reexamination Certificate
2002-04-15
2004-03-16
Le, N. (Department: 2862)
Electricity: measuring and testing
Magnetic
With means to create magnetic field to test material
C324S238000
Reexamination Certificate
active
06707297
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates generally to in-situ inspection of coated components and, more particularly, to in-situ eddy current inspection of coated components in turbine engines, for example airfoils in gas turbine engines and coated turbo components in locomotive diesel engines.
A gas turbine engine typically includes a compressor that supplies pressurized air to a combustor. The air is mixed with fuel in the combustor and ignited to generate hot combustion gases. The hot gases flow downstream to one or more turbines that extract energy from the hot gases to power the compressor and provide useful work, such as generating power at a power plant or powering an aircraft in flight.
Each turbine stage typically includes a turbine rotor assembly and a stationary turbine nozzle assembly for channeling combustion gases into the turbine rotor assembly disposed downstream therefrom. The turbine rotor assembly
50
commonly includes a number of circumferentially spaced apart rotor blades
20
extending radially outwardly from a rotor disk
30
that rotates about the rotor
10
, as illustrated schematically in FIG.
1
. Rotor blades generally include airfoils (also indicated by reference numeral
20
) and are commonly called “buckets” for land based turbine engines. As used here, the term “blade” encompasses “buckets” as well as blades. The rotor assembly is housed within a case
40
.
The stationary turbine nozzle assembly
60
includes a number of circumferentially spaced apart stationary vanes
21
radially aligned with the rotor blades
20
, as schematically illustrated in FIG.
2
. The stationary vanes are disposed between inner and outer bands
42
,
41
. The stationary vanes include airfoils (indicated by reference numeral
21
in
FIG. 2
) and are configured to direct the hot combustion gases to the downstream turbine rotor assembly, and, more particularly, toward the rotor blades
20
. Vanes are commonly called “nozzles” for land based turbine engines, and as used here the term “vane” encompasses both vanes and nozzles.
An exemplary airfoil
20
is illustrated in
FIG. 3
in cross-sectional view and includes a base metal
24
, for example formed of nickel superalloys, such as GTD111 or IN738. The core can be hollow or solid. The core is coated for protection against erosion and to render the airfoil suitable for use in high temperatures, with exemplary protective coatings
22
being NiCoCrAlY or MCoCrAlY. In addition, the airfoil may also include an outer ceramic coating
23
, to act as a thermal barrier (hereinafter a “thermal barrier coating”).
In response to the stress induced by thermal gradients in the airfoils and other operating conditions in gas turbine engines, cracks can develop in the airfoil coatings. An exemplary crack
52
is indicated in FIG.
3
. Although cracks generally terminate at the diffusion zone between the protective coating and the base metal, cracks do occasionally penetrate into the base metal.
In order to inspect airfoils for cracks, presently airfoils are removed from the rotor assembly and from the nozzle assembly during outage cycles for inspection, refurbishment, and determination of the remaining lives of the airfoils. The outage cycles occur about every 24,000 to 30,000 operational hours. In the current inspection process, the airfoils are first inspected by fluorescent penetrant inspection, to detect cracks in the coatings. When cracks are detected, the cracked airfoil is hand blended using a hand-held grinder to remove the cracks. A final fluorescent penetrant inspection is conducted to confirm that the cracks have been removed.
One drawback to the present airfoil inspection method is that removal of the airfoils from the rotor assembly and from the nozzle assembly and the subsequent fluorescent penetrant inspection of the airfoils are time and labor intensive, contributing to long and expensive gas turbine outages. In addition, the fluorescent penetrant inspection method detects only the presence of a crack and does not determine whether the crack is localized within the coatings
22
,
23
or has penetrated the base metal
24
, nor does the existing inspection method determine the depth of the crack. Moreover, the grinding performed while chasing the cracks progresses to the base metal in many instances, undesirably reducing the wall thickness of the airfoil.
Accordingly, it would be desirable to develop a method for in-situ inspection of gas turbine airfoils to determine the presence of cracks in the airfoils. It would further be desirable for the method to determine the crack depth and whether the crack has penetrated the base metal of the airfoil. In addition, it would be desirable for the method to employ nondestructive inspection techniques.
BRIEF DESCRIPTION OF THE INVENTION
Briefly, in accordance with one embodiment of the present invention, a method for in-situ eddy current inspection of at least one coated component is disclosed. The coated component includes a base metal and a coating disposed on the base metal. The method includes applying a drive pulse at a measurement position on an outer surface of the coated component, while the coated component is installed in an operational environment of the coated component. The method further includes receiving a response signal from the coated component, comparing the response signal with a reference signal to obtain a compared signal, analyzing the compared signal for crack detection, and determining whether a crack near the measurement position has penetrated the base metal, if the presence of the crack in the coating is indicated.
REFERENCES:
patent: 4048558 (1977-09-01), Goodman
patent: 4414508 (1983-11-01), Davis et al.
patent: 4468620 (1984-08-01), Vaerman
patent: 4644274 (1987-02-01), Casarcia
patent: 4929896 (1990-05-01), Lara
patent: 5015950 (1991-05-01), Rose et al.
patent: 5140264 (1992-08-01), Metala et al.
patent: 5152058 (1992-10-01), Legros
patent: 5391988 (1995-02-01), Kitagawa
patent: 5442285 (1995-08-01), Zombo et al.
patent: 5442286 (1995-08-01), Sutton, Jr. et al.
patent: 5781007 (1998-07-01), Partika et al.
patent: 6037768 (2000-03-01), Moulder et al.
patent: 6534975 (2003-03-01), Beeck et al.
Y. A. Plotnikov, S. C. Nath & C. W. Rose, “Defect Characterization in Multi-Layered Conductive Components with Pulsed Eddy Current”, Review of Quantitative Nondestructive Evaluation, vol. 21, 2002 American Institute of Physics, pp. 1976-1977.
H. A. Sabbagh, E. H. Sabbagh, R. Kim Murphy, “Applications of Eddy-Current Inversion”, Victor Technologies, LLC, pp. 149-150.
G. Antonelli, P. Crisafulli, G. Tirone, Qualification of a Frequency Scanning Eddy Current Equipment for Nondestrictive Characterization of New and Serviced High-Temperature Coatings, ASME Turbo EXPO 2001, Jun. 4-7, 2001, New Orleans, Louisiana, USA, pp. 1-2.
Batzinger Thomas James
Herd Kenneth Gordon
Nath Shridhar Champaknath
Plotnikov Yuri Alexeyevich
Rose Curtis Wayne
Aurora Reena
Clarke Penny A.
General Electric Company
Le N.
Patnode Patrick K.
LandOfFree
Method for in-situ eddy current inspection of coated... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for in-situ eddy current inspection of coated..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for in-situ eddy current inspection of coated... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3196333