U.S. patent application number 10/131137 was filed with the patent office on 2003-10-30 for way to manufacture inserts for steam cooled hot gas path components.
Invention is credited to Devine, Robert H., Downs, Justin, Peterson, Lance, Placko, James, Schaeffer, Jon C..
Application Number | 20030201087 10/131137 |
Document ID | / |
Family ID | 29215557 |
Filed Date | 2003-10-30 |
United States Patent
Application |
20030201087 |
Kind Code |
A1 |
Devine, Robert H. ; et
al. |
October 30, 2003 |
Way to manufacture inserts for steam cooled hot gas path
components
Abstract
A method for forming inserts for steam cooled hot gas path
components involves casting the inserts and laser drilling the cast
inserts with the ceramic casting core still in place. Thereafter,
the ceramic core is removed through the use of a leachant. By laser
drilling the holes with the ceramic core still in place, the
ceramic core acts as a backer during the laser drilling which
results in more precise drilling of the inserts and reduced
processing time.
Inventors: |
Devine, Robert H.;
(Schenectady, NY) ; Placko, James; (Schenectady,
NY) ; Downs, Justin; (Schenectady, NY) ;
Schaeffer, Jon C.; (Schenectady, NY) ; Peterson,
Lance; (Schenectady, NY) |
Correspondence
Address: |
NIXON & VANDERHYE P.C.
8th Floor
1100 North Glebe Rd.
Arlington
VA
22201-4714
US
|
Family ID: |
29215557 |
Appl. No.: |
10/131137 |
Filed: |
April 25, 2002 |
Current U.S.
Class: |
164/76.1 ;
164/132 |
Current CPC
Class: |
B22D 29/002 20130101;
B22C 9/04 20130101 |
Class at
Publication: |
164/76.1 ;
164/132 |
International
Class: |
B22D 029/00; B22D
025/00 |
Claims
What is claimed is:
1. A method of forming inserts for steam cooled hot gas path
components in a turbine, said method comprising: casting the
geometrical configuration of the insert; and laser drilling
impingement holes in the cast insert without removing a ceramic
casting core of the cast insert.
2. A method as claimed in claim 1, wherein the ceramic casting core
is removed by leachant.
3. A method as claimed in claim 2, wherein said casting comprises
pressure casting.
4. A method as claimed in claim 2, wherein said casting comprises
centrifugal casting.
5. A method as claimed in claim 2, wherein said casting comprises
squeeze casting.
6. A method as claimed in claim 2, wherein said casting comprises
counter gravity casting.
7. A method as claimed in claim 1, wherein the inserts are made of
a Ni-base superalloy.
8. A method as claimed in claim 2, wherein the inserts are made of
a Ni-base superalloy.
9. A method as claimed in claim 3, wherein the inserts are made of
a Ni-base superalloy.
10. A method as claimed in claim 4, wherein the inserts are made of
a Ni-base superalloy.
11. A method as claimed in claim 5, wherein the inserts are made of
a Ni-base superalloy.
12. A method as claimed in claim 6, wherein the inserts are made of
a Ni-base superalloy.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
[0001] The invention relates to a new way to manufacture inserts
for steam cooled hot gas path components.
[0002] Inserts are required in air and steam cooled nozzles to
provide impingement cooling to airfoil walls and ribs. The prior
art methods of production of inserts use sheet metal forming
operations, including welding and brazing, and electro discharge
machining of the holes. The problem with the prior art methods is
that the large complicated inserts combined with strict dimensional
tolerances result in 3D structures that have a very low yield
relative to design specifications.
[0003] The inventive process casts the inserts to tight tolerance
using any ceramic core casting process such as, for example,
pressure casting, centrifugal casting, squeeze casting or vacuum
casting (also known as counter gravity casting). Counter gravity
casting as employed by Hitchiner Manufacturing Co., Inc. of
Milford, N.H. uses metal dies with a vacuum pour to help fill thin
sections of the casting and eliminate porosity. After casting has
been completed, the core material is then used as a backer during
subsequent drilling operations. Finally, the core is removed by
acid leaching and the cast parts are machined, if necessary, to
finish specifications.
[0004] With the inventive manufacturing method certain commercial
and performance needs are met. For example, the inventive method
facilitates the production of complicated 3D insert geometries in a
Ni-base superalloy with thin walls and tight tolerances. The
inventive method also provides for accurate and precise drilling of
the cast inserts with improved processing times and fixtures.
[0005] The inventive method also solves the problems in the prior
art by using the ceramic core in the insert casting process to act
as a backer for laser drilling. The laser holes then facilitate the
use of leachant to quickly remove the core, speeding the
manufacturing process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 show a cast insert prior to laser drilling of the
insert holes;
[0007] FIG. 2 shows the case insert of FIG. 1 after laser drilling
of the insert holes but with the ceramic core still in place;
and
[0008] FIG. 3 shows the cast and drilled insert immersed in an acid
bath for removal of the ceramic core.
DETAILED DESCRIPTION OF THE INVENTION
[0009] The inventive method uses, for example, Hitchiner's thin
wall casting process to produce the insert geometry from a wax
model. The Hitchiner process substitutes counter gravity casting
for more conventional casting by, for example, gravity pouring.
[0010] In the basic investment casting process, wax replicas of the
desired castings are produced by injection molding. Depending on
the size of the castings, multiple wax replicas may be attached to
a central waxed stick, termed a sprue, to thereby form a casting
assembly. Thereafter, a ceramic shell is formed around the casting
or the casting assembly made up of the multiple wax replicas of the
desired castings. Next, the ceramic is dried and the wax is melted
out creating a negative impression of the casting assembly within
the ceramic shell.
[0011] If using the basic casting process, the casting shell is
filled with molten metal by gravity pouring. Conversely, in the
Hitchiner counter gravity process the ceramic casting shell is
placed within a vacuum and dipped into a hot metal melt which is
then siphoned up around and into the ceramic casting assembly.
After the metal is allowed to solidify on the ceramic casting the
vacuum is released and residual metal flows back in to the melt.
FIG. 1 schematically shows a cast insert 10 with ceramic core 12
shown in place by dotted lines. Also shown is laser drilling
apparatus 14 prior to the drilling process.
[0012] Preferably, the cast inserts are made from IN625 (Ni-base
superalloy). After the insert are cast into the desired geometry,
the ceramic core is not immediately leached out. Instead the
casting is put in a fixture for laser drilling holes with the
ceramic core still in place. The casting tolerances are such that a
fixture can handle a production run without a lot of rework.
[0013] The insert is then laser drilled with the ceramic core as a
backer. The backer stops backwall strikes and will act as a
breakthrough detector. FIG. 2 schematically shows insert 10 after
holes 16 have been drilled by laser drilling apparatus 14.
[0014] After the large number of holes (.about.300 holes/insert)
are drilled with laser precision, the ceramic core is leached out
with suitable caustics. FIG. 3 schematically shows ceramic 12 being
removed by immersing cast insert 10 in acid bath 18.
[0015] Another advantage of the inventive method is the reduction
in the number of heat treatments that the part goes through
relative to current state of the art processing. Reducing heat
treatments reduces the amount of distortion caused by residual
stresses and results in higher quality. The invention will produce
inserts and baffles for hot gas path hardware at a greater level of
performance and yield.
[0016] While the invention has been described in connection with
what is presently considered to be the most practical and preferred
embodiment, it is to be understood that the invention is not to be
limited to the disclosed embodiment, but on the contrary, is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims.
* * * * *