Metal fusion bonding – Process – Plural filler applying
Reexamination Certificate
2000-09-20
2001-08-21
Jones, Deborah (Department: 1775)
Metal fusion bonding
Process
Plural filler applying
C228S226000, C228S248100, C228S248500, C029S889100, C416S09700R, C416S09700R
Reexamination Certificate
active
06276597
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a brazing method for closing holes and, more particularly, to a brazing method and alloy for closing high pressure turbine blade tip cap holes to maximize filling of the holes, minimize porosity, improve oxidation resistance, and improve reliability.
During the manufacture of high pressure turbine blades of the type as shown in U.S. Pat. No. 5,232,343, tip cap holes are formed to locate casting cores. It is important to securely close such holes because otherwise cooling air leaks out of the tip rather than being directed over airfoil surfaces. The tip cap holes have a diameter on the order of 0.04 to 0.05 inch (about 0.1 cm to 0.13 cm). Heretofore such holes have been filled by injection with a 50% dense slurry of a fill alloy consisting of a relatively high melting point (“high melt”) component (H
1
) (about 45 wt %) intermixed with a relatively low melting point (“low melt”) component (L
1
) (about 55 wt %). The compositions of high melt and low melt components employed in prior practice are as follows:
High Melt Comp. (H1)
Low Melt Comp. (L1)
C
0.15-0.19 wt %
C
0.05 max wt %
Cr
13.7-14.3
Cr
14.8-15.8
Co
9.0-10.0
Co
9.5-11.0
Ti
4.8-5.2
Ta
3.0-3.8
Al
2.8-3.2
Al
3.2-3.7
W
3.7-4.3
B
2.1-2.5
Mo
3.7-4.3
Ni
Balance
W + Mo
7.7 min
Plus incidental
Ni
Balance
impurities
Plus incidental impurities
During brazing the low melt component particles melt to a liquid and, upon solidification, densify and bond the high melt component particles in the tip cap hole. A disadvantage of this approach has been that the cooled filling has a high internal porosity level which results in susceptibility to oxidation in service, and that a lack of fill condition exists due to a meniscus-type void that has formed upon cooling.
BRIEF SUMMARY OF THE INVENTION
Briefly, in accordance with this invention, a tip cap hole is loaded with a first composition comprising particles of a first alloy having a solidus temperature above the brazing temperature. The first composition is covered with a second composition comprising particles of a second alloy having a liquidus temperature below the brazing temperature. The second composition is heated to the brazing temperature to cause particles of the second alloy to melt to form a liquid of the second alloy which is carried into spaces between the particles of the first alloy by capillarity. The liquid of the second alloy is cooled to form a solid securely bonding the particles of the first alloy.
Other features of the present invention will be in part apparent and in part pointed out hereinafter.
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STN Search results for AMS 4782, Mar. 15, 2000.
Statement concerning B93, Mar. 2000.
Budinger David E.
Clarke Jonathan P.
Galley Ronald L.
Wustman Roger D.
General Electric Compnay
Gressel Gerry S.
Hess Andrew C.
Jones Deborah
Savage Jason
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