Information
-
Patent Grant
-
6660110
-
Patent Number
6,660,110
-
Date Filed
Monday, April 8, 200222 years ago
-
Date Issued
Tuesday, December 9, 200320 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 266 44
- 266 258
- 266 260
- 266 249
- 419 29
- 148 902
- 148 674
- 148 675
- 148 677
-
International Classifications
-
Abstract
A heat treatment assembly and heat treatment methods are disclosed for producing different microstructures in the bore and rim portions of nickel-based superalloy disks, particularly suited for gas turbine applications. The heat treatment assembly is capable of being removed from the furnace and disassembled to allow rapid fan or oil quenching of the disk. For solutioning heat treatments of the disk, temperatures higher than that of this solvus temperature of the disk are used to produce coarse grains in the rim of each disk so as to give maximum creep and dwell crack resistance at the rim service temperature. At the same time, solution temperature lower than the solvus temperature of the disk are provided to produce fine grain in the bore of the disk so as to give maximum strength and low cycle fatigue resistance.
Description
ORIGIN OF THE INVENTION
The invention described herein was made in the performance of work under a NASA contract and is subject to the provisions of Section 305 of the National Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat.435;42 U.S.C.2457).
FIELD OF THE INVENTION
The invention relates to an apparatus and method of operation thereof for heat treating a disk so as to produce a dual microstructure superalloy disk particularly suited for gas turbine applications.
BACKGROUND OF THE INVENTION
There are numerous incidents where operating conditions experienced by an article, or a component of a machine, place different material property requirements on different portions of the article or component. Examples include a crank shaft in an internal combustion engine, a piston rod in a hydraulic cylinder, planatary gears for an automotive transmission, and a turbine disk for a gas turbine engine. Gas turbine disks are often made from nickel-base superalloys, because these disks need to withstand the temperature and stresses involved in the gas turbine cycle. In the bore portion of the disk where the operating temperature is somewhat lower, the limiting material properties are often tensile strength and low-cycle fatigue resistance. In the rim portion of the disk, where the operating temperatures are higher than those of the bore, because of the proximity to the combustion gases, resistance to creep and cracking are the limiting properties.
Advanced nickel-base, gamma prime strengthened superalloys have been introduced to the field that allow improved engine performance through higher disk temperatures as compared to current engines. This is achieved by using high levels of gamma prime and refractory elements. However, there is a long term need for disks with higher rim temperature capabilities of 1400° F. or more. This increased temperature capability would allow higher compressor exit temperatures of a gas turbine and allow the full utilization of advanced combustion and airfoil concepts for aerodynamic applications. These disks require high creep resistance and dwell crack growth resistance of coarse grain microstructures in the rim region near 1400° F., while still maintaining the high strength and low cycle fatigue resistance of fine grain microstructures in the bore region near 800-1200° F.
The chief determinant of achieving grain size in powder metallurgy superalloy disks is the temperature at which the alloy is solution heat treated. As is known in the art, solution heat treatment is concerned with the solvus temperature; i.e., the temperature at which all of the gamma prime strengthening precipitate of the superalloy goes into solution. To perform the desired solution heat treatment in this invention, it is necessary to solution heat treat the disk in a way whereby the rim is heated to a higher solution heat treatment temperature than the bore. Furthermore, it would be necessary at the same time, as known in the art, to be able to directly quench the disk after the solution heat treatment to achieve high tensile strength and low cycle fatigue resistance in the bore and high creep resistance in the rim.
For most gas turbine applications, disks are currently heat treated at uniform solution temperature either below the gamma prime solvus temperature (subsolvus heat treatments), or above the solvus temperature (supersolvus heat treatments). Several recent approaches have been established which differ from the traditional subsolvus or supersolvus heat treatment. One approach, more fully described in U.S. Pat. No. 5,312,497, uses induction heating to preferentially heat the rim of a disk, while a pressurized gas is run through the bore of the disk to keep the bore and web cooler. Another approach, more fully described in U.S. Pat. Nos. 5,527,020 and 5,527,402, uses simpler top and bottom thermal caps placed over the bore of the disk to blow pressurized air through the center of a single disk, while the disk is being held at a constant temperature in a gas fired furnace. In this way, the bore of the disk is maintained at a sufficiently cooler temperature than the rim of the disk, thus, achieving desired subsolvus solution of the bore and desired supersolvus solution of the rim.
Uniform disk temperature heat treatments produce either fine or coarse grain microstructures throughout the disk. The fine grain microstructure has inferior creep and dwell crack growth resistance for rim service temperatures. Similarly, the coarse grain microstructure has inferior tensile and low cycle fatigue resistance for bore service temperatures. The approach described in U.S. Pat. No. 5,312,497, using induction heating of the rim with pressurized gas cooling of the bore can only be applied to one disk at a time, and is thereby very expensive. The practice of U.S. Pat. No. 5,312,497 is also very sensitive to induction coil-disk geometry tuning, disadvantageously yielding difficult process control. The approach described in U.S. Pat. Nos. 5,527,020 and 5,527,402, also is limited to heat treating one disk at a time. The practice of U.S. Pat. Nos. 5,527,020 and 5,527,402, while having reduced complexity compared to the practice of U.S. Pat. No. 5,312,497, still requires specialized air pressure lines going into a furnace that must remain operable for process viability. Accordingly, there still remains a need to provide heat treatment devices, and methods of use thereof, that provide different microstructures in the bore and rim portions of nickel-base superalloy disks without suffering the drawbacks of the prior art techniques.
OBJECTS OF THE INVENTION
It is a primary object of the present invention to provide a heat treatment apparatus and method of use thereof. The heat treatment yields rim portions of superalloy disks as having higher temperature capabilities associated with coarse grain microstructures, while at the same time maintaining high strength and low cycle fatigue resistance of fine grain microstructures in the bore portions of superalloy disks near 800-1200° F.
It is another object of the present invention to provide for different microstructures in the bore and rim portions of nickel-base superalloy disks and accomplish such by the use of standard production furnaces without auxiliary cooling.
It is further desired to provide differential microstructures in the rim and bore portions of nickel-base superalloy disks while still maintaining the option for rapid cooling upon completion of the solution heat treatment using conventional fan or oil quenching operations.
A further object of the present invention is to provide for design of the heat treatment device using a finite element computer code and solvus data of the disk alloy.
SUMMARY OF THE INVENTION
This invention is directed to a heat treatment apparatus and methods of use thereof which produce different microstructures in the bore and rim portions of nickel-base superalloy disks particularly suited for gas turbine engines.
In one embodiment, an apparatus is provided that is insertable and removable from a heat treatment furnace for differentially heat treating a superalloy disk to obtain a dual microstructure disk. The disk comprises an inner section termed the bore with a bore hole, an intermediate section termed the web portion, an outer section termed the rim portion, and first and second faces on opposite sides of the disk. The disk has predetermined diameter and thickness dimensions. The apparatus comprises first and second thermal blocks, respectively, arranged on the first and second faces of the disk. Each of the first and second thermal blocks has predetermined diameter and thickness dimensions related to the predetermined diameter and thickness dimensions of the disk by a predetermined relationship. The diameters of the first and second thermal blocks are less than the diameter of the disk. The first and second thermal blocks each have have upper and lower faces with the lower face of the first thermal block having an alignment pin positionable in correspondence with the bore hole of the disk and the upper face of the second thermal block having an alignment pin positionable in correspondence with the bore hole of the disk so that the first and second thermal blocks along with the disk are brought together and expose at least the rim portion of the disk. The apparatus further comprises first and second insulation jackets that surround the first and second thermal blocks. Each insulating jacket consists of an alignment plate, outer shell, and insulating media. The first and second alignment plates are respectively fastened to the upper face of the first thermal block and to the lower face of the second thermal block. The alignment plates have diameters greater than the thermal blocks. The apparatus still further comprises first and second outer shells respectively located outside of the first and second alignment plates with high temperature insulating media filling the cavity between the outer shells and thermal blocks.
The invention provides a method for differentially heat treating a superalloy disk having a gamma prime solvus temperature so as to obtain a dual microstructure disk. The method includes providing first and second thermal blocks respectively arranged on first and second faces of a disk. Each of the first and second thermal blocks has predetermined diameter and thickness dimensions related to the predetermined diameter and thickness dimensions of the disk by a predetermined relationship. The first and second thermal blocks each has upper and lower faces, with the lower face of the first thermal block having an alignment pin positionable in correspondence with the bore hole of the disk, and the upper face of the second thermal block having an alignment pin positionable in correspondence with the bore hole of the disk. The diameters of the first and second thermal blocks are less than the diameter of the disk. The method further includes providing first and second alignment plates each with a diameter greater than the diameter of the first and second thermal blocks and having means for being respectively fastened to the upper face of the first thermal block and to the lower face of the second thermal block. The method further comprises providing first and second outer shells respectively located outside of the first and second alignment plates with high temperature insulating media filling the cavity between the thermal blocks and outer shells. The method further includes the following steps: (1) positioning each of the alignment pins of the first and second thermal blocks in correspondence with the bore hole of the disk; (2) bringing together the first and second thermal block, the first and second shells with the associated high temperature insulating media and the disk thereby exposing the rim portion of the disk; (3) selectively attaching a thermocouple to either the first or second thermal block; (4) placing the brought together disk, the first and second thermal blocks, the first and second shells with the associated high temperature insulating media, and the thermocouple in a furnace; (5) heat treating the disk with heat sink assembly in a standard production furnace maintained at a temperature which is above the gamma prime solvus temperature of the disk for a first predetermined duration; (6) removing the disk and heat sink assembly from the furnace when the thermocouple reaches the subsolvus temperature of the disk alloy; (7) freeing the disk from the heat sink assembly; and (8) quenching the disk.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a schematic cross-sectional view of a disk shape for a gas turbine engine;
FIG. 2
is a cross-sectional view of a heat treatment apparatus of the present invention used for differentially heating a disk so as to provide a dual microstructure thereof;
FIG. 3
is composed of FIGS.
3
(A) and
3
(B) which show the predicted thermal gradients in a disk and the thermal block of the heat treatment apparatus at a specific time at an elevated temperature based on calculations obtained using a finite element computer code; and
FIG. 4
illustrates a macro etched section of a turbine disk created by the practice of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to the drawings, wherein the same reference number indicates the same element throughout, there is shown in
FIG. 1
an article which is differentially heat treated in accordance with the practice of the present invention. More particularly,
FIG. 1
shows a typical disk
10
for a gas turbine and is generally illustrated by reference number
10
. Each of the various disks
10
contemplated by the practice of the present invention has predetermined diameters and thickness dimensions covering a wide range of sizes all handled by a heat treatment device to be described hereinafter with reference to FIG.
2
.
The disk
10
has a typical diameter of thirteen (13) inches, a typical height of two (2) inches at its central region and a typical height of one (1) inch at its outer region. The disk
10
is comprised of an outer section rim portion, to be further defined hereinafter with reference to
FIG. 2
, occupying a predetermined region at the outer region of the disk
10
and generally shown by reference number
12
, an inner section bore portion
14
generally shown by reference number
14
, and a connecting or intermediate section web portion generally shown by reference number
16
. A central bore hole
18
, through the bore portion
14
, is illustrated and is an essential feature of the turbine disk
10
. The disk
10
additionally comprises a first face
20
, and a second face
22
, each of which extends over the rim, web, and bore portions of the disk
10
and are on opposite sides of the disk
10
. The disk
10
is advantageously solution heat treated by the use of a heat treatment device
24
of the present invention, which may be further described with reference to FIG.
2
.
FIG. 2
illustrates the heat treatment assembly
24
, which rests on a production heat treatment grate
32
of a standard gas-fired furnace to be described hereinafter and comprises top and bottom heat sinks
34
and
36
. The heat sinks,
34
and
36
, except for their insulative members to be further described, can be fabricated from any metal or alloy which can withstand the heat treatment temperatures. Carbon steel serves well for this purpose and can also be used to minimize cost of the heat treatment assembly
24
. The heat treatment assembly
24
also contains a thermocouple
26
that is preferably placed in a thermal block
28
near the bore portion
14
of the disk
10
. The thermocouple
26
is connected to a temperature indicator
30
by way of signal path
30
A. The thermocouple
26
derives an electrical signal representative of the temperature of the thermal block
28
and, more importantly, the temperature of the bore portion
14
of the disk
10
.
Each heat sink
34
or
36
has four components; a thermal block, an alignment pin, an alignment plate, and an outer shell, which for heat sink
34
are respectively shown with reference numbers
28
,
44
,
46
, and
48
and, similarly, these four components are respectively shown for heat sink
36
with reference numbers
50
,
52
,
54
, and
56
. For the disk
10
shown in
FIG. 1
, the thermal block
28
has typical dimensions of a diameter of six (6) inches and a height of two (2) inches, whereas thermal block
50
has typical dimensions of a diameter of six (6) inches and a height of three (3) inches. The alignment plates
46
and
54
have typical dimensions of a diameter of eight (8) inches and a thickness of 0.25 inches. The outer shells
48
and
56
are essentially pipe sections preferably comprised of carbon steel and have a typical diameter of eight (8) inches.
The rim portion
12
is defined herein as that portion of the disk
10
extending outside of the shells
48
and
56
. The thermal blocks
28
and
50
are defined herein as having diameters which are less than the diameters of the shells
48
and
56
and also less than the diameters of the disk
10
receiving the heat treatment of the present invention.
The thermal blocks
28
and
50
are solid metal cylinders and are used to chill the central portion of the disk
10
. The alignment pins
44
and
52
and alignment plates
46
and
54
are respectively connected by appropriate means, such as bolts, to the thermal blocks
28
and
50
to assure maintaining the concentricity of the disk
10
, thermal blocks
28
and
50
, and outer shells
48
and
56
during the heat treatment of the disk
10
to be described hereinafter. The alignment pins
44
and
52
and the alignment plates
46
and
54
provide concentric alignment of the thermal blocks
28
and
50
and the outer shells
48
and
56
relative to the geometric center of the disk
10
so as to ensure that the coarse and fine grain macrostructures resulting from the practice of the present invention, to be further described hereinafter with respect to
FIG. 3
, are also concentric after disk
10
is heat treated.
Insulating jackets, which are comprised of the outer shells
48
and
54
and high temperature insulating media, generally identified by reference number
58
, minimize the temperature rise of the thermal blocks
28
and
50
and the central portion of the disk
10
. Any high temperature insulating media, such as Kaowool™, can be used to fill the gaps between the outer shells
48
and
56
and the thermal blocks
28
and
50
as shown in FIG.
2
.
The thermal block
28
has an upper face
28
A and a lower face
28
B, similarly, the thermal block
50
has an upper face
50
A and a lower face
50
B. The lower face
28
B of the thermal block
28
is mated with face
20
of the disk
10
, whereas the upper face
50
A of the thermal block
50
is mated with the face
22
of the disk
10
. The thermal block
50
has the alignment pin
52
protruding from its upper face
50
A, whereas the thermal block
28
has an alignment pin
44
protruding from its lower face
28
B. The alignment pins
44
and
52
are positionable in correspondence with the bore hole
18
of the disk
10
. The diameters of the thermal blocks
28
and
50
are less than the diameter of the disk
10
by a predetermined amount so as to expose the outer periphery of the disk
10
.
The alignment plates
46
and
54
have respective peripheries
46
A and
54
A. Further, the alignment plates
46
and
54
, each has a diameter greater than the diameter of the thermal blocks
28
and
50
and each has appropriate means, such as bolts (not shown) for being respectively fastened to the upper face
28
A of the thermal block
28
and to the lower face
50
B of the thermal block
50
.
The outer shells
48
and
56
are respectively located outside of, but near the periphery
46
A and
54
A of the alignment plates
46
and
54
. The outer shells
48
and
56
are dimensioned so as to slide over the respective alignment plates
46
and
54
. The outer shells
48
and
56
are preferably spaced apart from each other by an amount, which is somewhat greater than the predetermined thickness of the rim portion
12
of the disk
10
. For one embodiment, the outer shell
48
rests on the disk
10
, whereas the outer shell
56
is free of contact with the disk
10
. This results in maximum thermal contact of disk
10
and thermal block
50
.
The heat treatment assembly
24
still further preferably comprises a special purpose rack
62
comprised of a heat resistant material and having a frame
64
for holding the disk
10
. The frame
64
also has a supporting legs
66
. The frame
64
has a clearance hole
68
with a typical diameter of nine (9) inches so that the frame
64
may slide over the outer shell
56
.
The heat sinks
34
and
36
are designed to enhance and maximize the natural thermal gradient between the interior bore
14
and periphery rim
12
of the disk
10
. These heat sinks
34
and
36
and the accompanying thermal cycle, to be further described hereinafter with reference to
FIG. 3
, operatively cooperate to produce a fine grain bore
14
and a coarse grain rim
12
in the disk
10
in a standard furnace without the aid of auxiliary cooling. The dimensions of the thermal blocks
28
and
50
and the outer shells
48
and
56
, having the typical values previously described with reference to
FIG. 2
, are related to the dimensions of the disk
10
by a predetermined relationship that may be determined using commercially available finite element heat transfer computer code. An example of one embodiment of the present invention and the thermal gradients thereof are depicted in
FIG. 3
, which is composed of FIGS.
3
(A) and
3
(B).
FIG. 3
shows the thermal gradient in a typical disk
10
used in a turbine application and schematically illustrated in
FIG. 3
, as having mated thereto a thermal block, such as thermal block
28
, and an insulating jacket, defined by outer shell
48
. The thermal gradients are illustrated for a specified time at an elevated temperature.
FIGS.
3
(A) and
3
(B) are interrelated, wherein FIG.
3
(A) shows a Finite Element Analysis (FEA) prediction and FIG.
3
(B) illustrates associated temperatures. The (FEA) prediction is the condition occurring after subjecting the disk
10
and thermal block
28
to an elevated temperature of 2150° F. for a duration of about 1.8 hours. FIG.
3
(B) illustrates a temperature range
70
segmented into three temperatures ranges, which define regions
72
,
74
, and
76
having the clear and two different shaded portions shown in FIG.
3
(B). These regions
72
,
74
and
76
are shown in FIG.
3
(A) as being associated with thermal block
28
and disk
10
. As can be seen in
FIG. 3
, the temperature of the thermal block
28
and more importantly the central portion of the disk
10
corresponds to the lowest
72
(subsolvus) region, whereas the temperature at the rim
12
of the disk
10
corresponds at the highest
76
(supersolvus) region. Region
72
represents the fine grain region of the disk
10
and region
76
represents the coarse grain region of the disk
10
after completion of the heat treatment of the invention.
In operation, and in reference to
FIG. 2
, the first and second heat sinks
34
and
36
are selected in a manner as previously described and assembled with the disk
10
and heat treatment rack
62
on a standard production heat treatment grate
32
. Thermocouple
26
is then preferably attached to thermal block
28
, but it may alternatively be attached to thermal block
50
.
The solution heat treatment of the present invention may be provided by standard gas-fired furnaces which may be of the type used by Ladish Company Inc., Wyman-Gordon Forging, or other heat treatment companies.
The heat treatment cycle is dependent on the alloy making up the disk
10
, that is, its gamma prime solvus temperature and its incipient melting point. The method of the present invention first handles the heat treatment assembly
24
, which is at room temperature, so as to be inserted into a furnace maintained at a temperature above the gamma prime solvus temperature of the alloy. It is desired that the furnace temperature be as high as possible without producing incipient melting of the alloy. For the class of alloys used for turbine applications, the upper limit of the furnace temperature is generally less than 2200° F. The method of the invention monitors the temperature of the bore portion
14
of the disk
10
by means of the thermocouple
26
and temperature indicator
30
.
The heat treatment assembly
24
is removed from the furnace when the thermocouple
26
in the thermal block
28
reaches the subsolvus solution temperature of the disk alloy which is generally less than about 2100 F. At this point, the rim
12
of the disk
10
will have exceeded the solvus temperature of the alloy and, therefore, have a coarse grain microstructure, while the bore portion
14
of the disk
10
will have been maintained below the solvus temperature and, therefore, have a fine grain microstructure.
The heat sinks
34
and
36
are removed prior to the quenching to facilitate faster cooling of the disk
10
. As is known in the art, this rapid quenching achieves high strength and creep resistance in the disk
10
. Rapid removal of the heat sinks are facilitated by rack
62
. Upon lifting rack
62
, disk
10
and heat sink
34
can be removed from the furnace without heat sink
36
. Once rack
62
, disk
10
, and heat sink
34
are out of the furnace, heat sink
34
can be rapidly removed from disk
10
and rack
62
. This can be accomplished by any number of techniques readily available at heat treat shops which routinely handle metal parts at high temperature as heat sink
34
is not clamped to disk
10
. Once heat sink
34
is removed, disk
10
now resting on rack
62
can be moved to existing cooling facilities for fan cooling or oil quenching.
It should now be appreciated that the practice of the present invention provides for a heat treatment assembly
24
in which the disk
10
is brought into contact with the heat sinks
34
and
36
, and the solution treatment is performed in a desired manner. The heat sinks
34
and
36
are brought together with the disk
10
in a non-clamped manner so as to allow a relatively easy disassembly thereof. The removal of the heat sinks
34
and
36
allow the disk
10
to be easily moved and placed into an appropriate quenching station by moving the special rack
62
carrying the disk
10
.
The heat treatment assembly
24
provides a compact arrangement for performing the desired heat treatment of the disk
10
. Because of this compact arrangement multiple disks can be heat treated simultaneously, in accordance with the practice of the present invention, in a standard production furnace so as to decrease cost with minimal modification to the present invention.
In the practice of the invention, the method hereinbefore described was performed on a disk
10
mated with the heat treatment assembly
24
of
FIG. 2
, and some of the results thereof may be further described with reference to FIG.
4
.
FIG. 4
shows macroetched section of an actual superalloy disk
10
after receiving the heat treatment of the present invention utilizing the heat treatment assembly
24
. From
FIG. 4
it should be noted that a fine grain region exists in the center of disk
10
(clear texture) at the bore portion
14
and a coarse grain region exists at the rim portion
12
of the disk
10
(speckled texture). The transition between the fine and coarse grain regions is generally identified in
FIG. 4
by dimensional line
78
. The grain size of the circle portion A located in the center of the disk
10
at the bore portion
14
is about 13 ASTM (American Society for Testing and Materials) and the grain size of the circle portion B located at the rim portion
12
of the disk
10
is about 7 ASTM.
It should now be appreciated that the practice of the present invention provides for a method to handle various articles, some of which are particularly suited as gas turbine disk, and all of which have a dual microstructure in which the rim portion of the article being treated has creep and dwell crack growth resistance of coarse grain microstructure operable at a temperature near 1400° F., while still maintaining the high strength and low cycle fatigue resistance of fine grain microstructure in the bore portion of the article being treated operable at a temperature of 800-1200° F.
It should now be appreciated that the practice of the present invention provides for a heat treatment assembly that accommodates superalloy disks. The practice of the present invention yields these disks having high creep resistance and dwell crack growth resistance of coarse grain microstructure in the rim portion
12
with an operating temperature near 1400° F., while at the same time maintaining high strength and low cycle fatigue resistance of fine grain microstructure in the bore region
14
having an operating temperature of between 800-1200° F.
The invention has been described with reference to the preferred embodiments and some alternates thereof. It is believed that many modifications and alterations to the embodiments as discussed herein will readily suggest themselves to those skilled in the art upon reading and understanding the detailed description of the invention. It is intended to include all such modifications and alterations insofar as they come within the scope of the present invention.
Claims
- 1. An apparatus insertable and removable from a heat treatment furnace for differentially heat treating a superalloy disk to obtain a dual microstructure disk, the disk comprising an inner section termed the bore portion with a bore hole, an intermediate section termed the web portion, an outer section termed the rim portion, and first and second faces on opposite sides of the disk, said disk having predetermined diameter and thickness dimensions for each of said rim and bore portions, said apparatus comprising:first and second thermal blocks respectively arranged on said first and second faces of said disk, each of said first and second thermal blocks having predetermined diameter and thickness dimensions related to said predetermined diameter and thickness dimensions of said disk by predetermined relationship, said diameters of said first and second thermal blocks being less than said diameter of said disk, said first and second thermal blocks each has upper and lower faces with the lower face of the first thermal block having an alignment pin positionable in correspondence with said bore hole of said disk and the upper face of the second thermal block having an alignment pin positionable in correspondence with said bore hole of said disk so that said first and second thermal blocks along with said disk are brought together and expose at least the rim portion of the disk; first and second alignment plates each with a diameter greater than the diameter of said first and second thermal blocks and with a periphery and having means for being respectively fastened to the upper face of the first thermal block and to the lower face of the second thermal block; and first and second outer shells located outside of the periphery of said first and second alignment plates with high temperature insulating media filling the cavity between the outer shells and thermal blocks.
- 2. The apparatus according to claim 1 wherein said first and second shells are spaced apart from each other by an amount which is greater than said predetermined thickness of said rim portion.
- 3. The apparatus according to claim 1, further comprising a rack comprised of a heat resistant material and having a frame for holding and carrying said disk, said frame having supporting legs.
- 4. The apparatus according to claim 1, wherein said thermal blocks, said alignment plates and said outer shells are comprised of a carbon steel material.
- 5. The apparatus according to claim 1, wherein said apparatus further comprises a thermocouple capable of being attached to either said first or second thermal block.
- 6. A method for differentially heat treating a superalloy disk having a gamma prime solvus temperature to obtain a dual microstructure disk, said disk comprising an inner section termed the bore portion with a bore hole, an intermediate section termed the web portion, an outer section termed the rim portion, and first and second faces on opposite sides of the said disk, said disk having predetermined diameter and thickness dimensions for said rim and bore portions,providing first and second thermal blocks respectively arranged on said first and second faces of said disk, each of said first and second thermal blocks having predetermined diameter and thickness dimensions related to said predetermined diameter and thickness dimensions of said disk by a predetermined relationship, said diameter of said first and second thermal blocks being less than said diameter of said disk, said first and second thermal blocks each has upper and lower faces with the lower face of the first thermal block having an alignment pin positionable in correspondence with said bore hole of said disk and the upper face of the second thermal block having an alignment pin positionable in correspondence with said bore hole of said disk; providing first and second alignment plates each with a diameter greater than the diameter of said first and second thermal blocks and with a periphery and having means for being respectively fastened to the upper face of the first thermal block and to the lower face of the second thermal block; providing first and second outer shells respectively located outside of the periphery of said first and second alignment plates with high temperature insulating media filling the cavity between the outer shells and thermal blocks; positioning each of said alignment pins of said first and second thermal blocks in correspondence with said bore hole of said disk; bringing together said first and second thermal blocks, first and second alignment plates, the first and second shells with the associated high temperature insulating media, and said disk and exposing said rim portion; selectively attaching a thermocouple to either said first or second thermal block; placing the brought together disk, the first and second thermal blocks, first and second alignment plates, first and second shells with the associated high temperature insulating media, and the thermocouple in a furnace; heat treating the disk in a furnace at a temperature which is above said gamma prime solvus temperature of said disk for a first predetermined duration; removing the disk and heat treatment assembly from furnace when thermocouple reaches the subsolvus temperature of said disk alloy; freeing said disk from heat treatment assembly; and quenching said disk.
- 7. The method according to claim 6 further providing a special purpose rack designed to facilitate rapid removal of heat sink assembly from said disk and also accomplish said quenching step.
- 8. The method according to claim 6, wherein said furnace temperature is above said gamma prime solvus temperature and is also selected to be below the incipient melting temperature of said disk alloy.
US Referenced Citations (10)