U.S. patent application number 11/146571 was filed with the patent office on 2005-11-03 for method for attaching a porous metal layer to a metal substrate.
Invention is credited to Charlebois, Steven J., Clarke, William, Medlin, Dana J., Pletcher, Dirk L., Scrafton, Joel G., Shetty, H. Ravindranath, Swarts, Dale.
Application Number | 20050242162 11/146571 |
Document ID | / |
Family ID | 30115525 |
Filed Date | 2005-11-03 |
United States Patent
Application |
20050242162 |
Kind Code |
A1 |
Medlin, Dana J. ; et
al. |
November 3, 2005 |
Method for attaching a porous metal layer to a metal substrate
Abstract
A method for attaching a porous metal layer to a dense metal
substrate, wherein the method is particularly useful in forming
orthopedic implants such as femoral knee components or acetabular
cups. The method, in one embodiment thereof, comprises providing a
structured porous layer; providing a dense metal substrate;
providing a binding mixture; applying the binding mixture to the
exterior of the substrate; placing the porous layer against the
substrate such that the binding mixture is disposed there between
forming an assembly; and heat treating the assembly to
metallurgically bond the porous layer to the substrate.
Inventors: |
Medlin, Dana J.; (Warsaw,
IN) ; Charlebois, Steven J.; (Goshen, IN) ;
Clarke, William; (Warsaw, IN) ; Pletcher, Dirk
L.; (Walkerton, IN) ; Scrafton, Joel G.;
(Leesburg, IN) ; Shetty, H. Ravindranath; (Warsaw,
IN) ; Swarts, Dale; (Warsaw, IN) |
Correspondence
Address: |
ZIMMER TECHNOLOGY, INC.
150 N. WACKER DRIVE
SUITE 1200
CHICAGO
IL
60606
US
|
Family ID: |
30115525 |
Appl. No.: |
11/146571 |
Filed: |
June 7, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11146571 |
Jun 7, 2005 |
|
|
|
10455846 |
Jun 6, 2003 |
|
|
|
6945448 |
|
|
|
|
60389615 |
Jun 18, 2002 |
|
|
|
Current U.S.
Class: |
228/194 |
Current CPC
Class: |
A61F 2002/30787
20130101; A61L 27/04 20130101; A61F 2002/30978 20130101; A61F
2310/00023 20130101; A61L 27/56 20130101; A61F 2002/3401 20130101;
A61F 2/3859 20130101; A61F 2310/00029 20130101; B22F 7/064
20130101; A61F 2/30907 20130101; A61F 2/3094 20130101; A61L 27/30
20130101; A61F 2310/00407 20130101; A61F 2/30767 20130101; B22F
7/004 20130101; A61F 2310/00544 20130101; A61F 2002/30967 20130101;
A61F 2002/30968 20130101; C23C 26/00 20130101 |
Class at
Publication: |
228/194 |
International
Class: |
B23K 020/00 |
Claims
We claim:
1. A method for attaching a porous metal structure to a metal
substrate, the method comprising: providing a metal substrate;
providing the porous metal structure; contouring a surface of the
porous metal structure; placing the porous structure against the
substrate such that the contoured surface of the porous structure
is in contact with the substrate, thereby forming an assembly; and
heating the assembly to metallugically bond the porous structure
and the substrate.
2. The method of claim 1, wherein the metal substrate comprises a
metal selected from the group consisting of cobalt, cobalt alloys,
titanium and titanium alloys.
3. The method of claim 1, wherein the contouring step comprises
machining the surface of the porous metal structure.
4. The method of claim 1, wherein the contouring step comprises
electro-discharge machining the surface of the porous metal
structure.
5. The method of claim 1, wherein the heating step comprises:
heating the assembly at about 100.degree. C. to 600.degree. C. for
about 1 to 4 hours; and further heating the assembly at about
800.degree. C. to 1600.degree. C. for about one hour to about four
hours.
6. The method of claim 1, wherein the heating step is performed in
an inert environment comprising a gas selected from the group
consisting of argon and helium.
7. The method of claim 1, wherein the heating step is performed in
an at least partial vacuum.
8. A method for attaching a porous metal structure to a metal
substrate, the method comprising: providing a metal substrate;
providing the porous metal structure; contouring a surface of the
porous metal structure; placing the porous structure against the
substrate such that the contoured surface of the porous metal
structure is disposed against the substrate, thereby forming an
assembly; and applying heat and pressure to the assembly to
metallugically bond the porous structure and the substrate.
9. The method of claim 8, wherein the metal substrate comprises a
metal selected from the group consisting of cobalt, cobalt alloys,
titanium and titanium alloys.
10. The method of claim 8, wherein the contouring step comprises
machining the surface of the porous metal structure.
11. The method of claim 8, wherein the contouring step comprises
electro-discharge machining the surface of the porous metal
structure.
12. The method of claim 8, wherein the heating step comprises:
heating the assembly to about 800.degree. C. to 1600.degree. C. for
about one hour to about four hours, under a clamping pressure of
between about 200 p.s.i. and about 1200 p.s.i.
13. The method of claim 8, wherein the step of applying heat and
pressure is in an inert environment comprising a gas selected from
the group consisting of argon and helium.
14. The method of claim 8, wherein the step of applying heat and
pressure is performed in an at least partial vacuum.
15. A method for attaching a porous metal structure to a metal
component of an orthopedic implant, the method comprising:
providing a metal component, having a desired shape and a bone
contacting surface; providing the porous metal structure in a
desired shape; contouring a surface of the porous metal structure;
placing the porous structure against the bone contacting surface of
the metal component such that the contoured surface of the porous
structure is in contact with the metal component, thereby forming
an assembly; and heating the assembly to metallugically bond the
porous structure and the substrate.
16. A method for attaching a porous metal structure to a metal
component of an orthopedic implant, the method comprising:
providing a metal component, having a desired shape and a bone
contacting surface; providing the porous metal structure in a
desired shape; contouring a surface of the porous metal structure;
placing the porous structure against the bone contacting surface of
the metal component such that the contoured surface of the porous
structure is in contact with the metal component, thereby forming
an assembly; and applying heat and pressure to the assembly to
metallugically bond the porous structure and the substrate.
Description
RELATED APPLICATION
[0001] This application is a divisional of co-pending U.S. patent
application Ser. No. 10/455,846, filed on Jun. 6, 2003 which is a
non-provisional of U.S. Provisional Patent Application Ser. No.
60/389,615, filed on Jun. 18, 2002, the disclosure of which is
hereby explicitly incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to orthopedic implants of the
type having a porous surface into which bone tissue can grow or
bone cement can enter and, more particularly, to a method of
bonding a porous metal structure, such as porous titanium or porous
tantalum onto a metal substrate preferably comprising a
titanium-based or cobalt-based alloy.
[0004] 2. Description of the Related Art
[0005] Orthopedic implant devices commonly include a porous
structure of desired thickness, generally 0.5 to 5.0 mm, on the
bone contacting surface of the implant to promote bone growth there
through and to enhance attachment of the device to adjacent bone
tissue. Growth of bone into an implant is advantageous in that the
same allows for increased fixation of the implant.
[0006] Accordingly, it is desirable to promote as much bone growth
into an implant as possible. Various methods have been developed
for manufacturing an orthopaedic implant device having a porous
surface, including plasma spraying of metal powder, sintering of
metal beads, and diffusion bonding of metal wire mesh. See for
example, the following patents, the disclosures of which are hereby
incorporated by reference and briefly described herein.
[0007] U.S. Pat. No. 3,906,550 to Rostoker et al. discloses a
porous metal structure adapted for attachment to a prosthesis. The
fiber metal is molded into the desired shape using dies. The fiber
metal is then sintered together to form metallurgical bonds within
the pad and between fiber metal pad and the substrate.
[0008] U.S. Pat. No. 3,605,123 to Hahn discloses a metallic bone
implant having a porous metallic surface layer. The porous layer
may be secured to the implant by a plasma spray method or by other
suitable means.
[0009] U.S. Pat. No. 4,636,219 to Pratt et al. discloses a
prosthesis including a porous surface comprised of a layered metal
mesh structure and a process for fabricating the mesh screen
structure for bonding to the prosthesis. The mesh may be bonded to
a thin substrate which can then be cut or formed and applied to the
body of a prosthesis on a flat surface or contoured into specific
shapes by forming.
[0010] U.S. Pat. No. 4,570,271 to Sump discloses a prosthesis with
a porous coating in which the porous coating is preformed directly
into the desired shape which corresponds to the preselected surface
of the prosthesis. The preformed porous coating is then overlaid
onto the preselected surface, compressed, and heated to adhere the
preformed porous coating to the prosthesis.
[0011] U.S. Pat. No. 3,855,638 to Pilliar described the bonding
process to a prosthetic device having a solid metallic substrate
with a porous coating adhered thereto. A slurry of metallic
particles was applied to the substrate, dried and then sintered to
establish metallurgical bond between particles and the
substrate.
[0012] U.S. Pat. Nos. 5,198,308 and 5,323,954 entitled "Titanium
Porous Surface Bonded to a Cobalt-Based Alloy Substrate in
Orthopaedic Implant Device and Method of Bonding Titanium to a
Cobalt-Based Alloy Substrate in an Orthopaedic Implant Device"
which are assigned to assignee of the present invention teaches
diffusion bonding of titanium fiber metal pad porous layer to
Co--Cr--Mo alloy implants with the use of a thin titanium and or
L-605 alloy foil to increase the bond strength of the coating to
the substrate and corrosion resistance of the implant.
[0013] U.S. Pat. No. 5,104,410 granted to Chowdhary discloses the
method of making a surgical prosthetic device, comprising of a
composite structure having a solid metal substrate and a porous
coating with multiple sintered layers. The porous coating has an
external layer to accept bone ingrowth and the chemical composition
of the external layer is same as the intermediate layer between the
porous coating and the implant surface. The intermediate layer
bonds the external porous layer to the substrate. These layers are
applied in a process of multiple sintering where each successive
layer is individually sintered to the substrate or the proceeding
layer, as applicable. This process provides a porous layer having
increased strength of attachment between the substrate and the
external porous layer.
[0014] Titanium is a known biocompatible metal that is often used
in orthopedic applications. Porous titanium or porous titanium
alloy can be used on the bone contacting surface of an orthopedic
implant to promote bone growth there through. Tantalum is another
known biomaterial. Tantalum is known to be particularly adept at
promoting bone growth. Implex, Inc. markets a structured porous
tantalum metal biomaterial, described in U.S. Pat. No. 5,282,861,
for orthopedic use under the trade name HEDROCEL.RTM.. HEDROCEL is
described as being more than 80% porous, and closely resembles
human trabecular bone in both physical and mechanical properties.
In spite of the value of using a porous layer in orthopedic
implants, bonding porous metal to a metal substrate such as cobalt
alloy or titanium alloy has been difficult, especially in the case
of HEDROCEL. The reason for this difficulty is that metallurgically
bonding two components generally requires a large amount of contact
between the surfaces at which the bond is desired. The porosity of
HEDROCEL results in sparse contact with an opposing metal
substrate, thereby making sintering or diffusion bonding difficult.
Moreover, this porosity also makes it difficult to maintain the
narrow dimensioning tolerances for machined HEDROCEL components.
The binding mixture, therefore, also serves to fill in "gaps" or
"spaces" that may exist between a HEDROCEL porous layer of desired
shape and a corresponding metal substrate.
[0015] Thus, a need exists for a method of bonding a porous metal
structure to a metal substrate.
[0016] An additional need exists for a method of bonding a porous
metal surface to a component of an orthopedic implant device
comprising a solid metal, such as cobalt-chrome alloy or titanium
alloy.
SUMMARY OF THE INVENTION
[0017] The present invention provides a method of bonding a porous
metal layer, comprising for example, HEDROCEL, to a titanium alloy
or cobalt alloy substrate. More specifically, the bonding process
of the present invention involves bonding a porous metal layer
directly onto titanium alloy or cobalt alloy surfaces using a
sintering or diffusion bonding process that includes a means for
producing good surface contact between the porous metal and the
substrate.
[0018] In one embodiment, the method of the present invention
comprises: providing a metal substrate; providing a binding
mixture; providing a porous metal structure; applying the mixture
to the substrate or to the porous metal; placing the porous metal
structure against the substrate such that the binding mixture is
disposed between the porous metal structure against the substrate,
thereby forming an assembly; and subjecting the assembly to heat
and/or pressure thereby forming an assembly; and subjecting the
assembly to heat and/or pressure thereby metallurgically bonding
the porous metal to the substrate In this first embodiment, the
binding mixture is used to provide contact between the porous metal
and the substrate.
[0019] In a another embodiment, the method of the present invention
comprises: providing a metal substrate; providing the porous metal
structure; "contouring" the surface of (as defined subsequently
herein) of the porous metal structure; placing the porous metal
structure against the substrate, thereby forming an assembly; and
subjecting the structure to heat and/or pressure to metallurgically
bond the porous metal structure to the substrate. In this second
embodiment, surface contact between the porous metal structure and
the substrate is achieved by contouring the surface of the porous
metal prior to placing it against the substrate.
[0020] The invention, in another form thereof, further provides a
method of making an orthopedic implant having a porous metal layer
bonded to a metal component of an implant.
[0021] An advantage of the bonding method of the present invention
is that a porous metal structure can be bonded to titanium-based
and cobalt-based alloy substrates.
[0022] A further advantage of the bonding method of the present
invention is that a single bonding process is employed thereby
protecting the metallurgical properties of the component alloys of
the assembly.
[0023] Another advantage of the present invention is that
orthopaedic implant devices produced according to the present
invention comprise a porous metal surface provided on
titanium-based and cobalt-based alloy substrates with enhanced bond
strength and corrosion resistance.
[0024] Other advantages of the present invention will be apparent
to those of skill in the art upon reviewing the appended
specification, drawings, and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The above-mentioned and other features and objects of this
invention, and the manner of obtaining them, will become more
apparent and the invention itself will be better understood by
reference to the following description of an embodiment of the
invention taken in conjunction with the accompanying drawings and
claims, wherein:
[0026] FIG. 1 is a diagrammatic view of a first embodiment of the
present invention.
[0027] FIG. 2 is a diagrammatic view of a second embodiment of the
present invention.
[0028] FIG. 3 is a diagrammatic view of a third embodiment of the
present invention.
[0029] FIG. 4 is a perspective view of the femoral component of an
endoprosthetic knee joint constructed according to the present
invention.
[0030] FIG. 5 is a perspective view an acetabular cup constructed
according to the present invention.
[0031] Corresponding reference characters indicate corresponding
parts throughout the several views. The exemplifications set out
herein illustrate one preferred embodiment of the invention, in one
form, and such exemplifications are not to be construed as limiting
the scope of the invention in any manner.
DETAILED DESCRIPTION OF THE INVENTION
[0032] Referring now to FIG. 1, there is shown a diagrammatic view
of a first embodiment of the present invention. Generally, Block
110 represents providing a metal substrate. In the present
invention, the term "metal substrate" refers to titanium based or
cobalt based alloys as are often used in orthopedic applications.
Titanium alloys such as Ti-6Al-4V alloy or Ti-6Al-7Nb alloy having
a rating of ASTM F-136 or F-1295 respectively are preferred. Cobalt
based alloys, specifically cast Co--Cr--Mo alloy or wrought
Co--Cr--Mo alloy, having an ASTM designation of F-75 or F-1537
respectively, may also be used. In some instances, it is desirable
to use a cobalt based alloy having a layer of commercially pure
titanium or titanium alloy plasma sprayed thereon. The above stated
metals are preferred because of their strength, corrosion
resistance and biocompatibility. In the orthopedic applications for
which the method of the present invention will most commonly,
although not exclusively, be used, the metal substrate will be
shaped in a manner desirable to function as a component of an
orthopedic implant, for example, an acetabulat cup as shown in FIG.
5 of the present invention or a femoral component for an
endoprosthetic knee as shown in FIG. 4 of the present invention.
However, those skilled in the art will appreciate that the present
invention is applicable to any application wherein one desires to
metallurgically bond a porous metal layer to a metal substrate.
[0033] Referring still to FIG. 1, there is shown Block 120 which
represents providing a porous metal layer. In a preferred
embodiment, a porous tantalum structure is used. The porous metal
layer is preferably provided in a desired shape suitable for a
particular application. For example, a hemispherical shape may be
used as a shell for an acetabular cup orthopedic implant. The
porous metal layer may also be provided as a pad for use on the
bone contacting surface of a standard femoral component for an
orthopedic knee implant.
[0034] In order to provide a strong metallurgical bond (i.e. a pull
apart strength of at or above about 2900 p.s.i.) between the metal
substrate and porous metal layer via sintering or diffusion
bonding, there must be sufficient surface contact between the
components. Those skilled in the art will appreciate that, on a
microscopic level, neither the surface of the metal substrate, nor
the surface of the porous metal layer is perfectly contoured. Thus,
a less than critical amount of surface contact for producing a
metallurgical bond will exist between a porous metal layer and a
metal substrate disposed directly against one another, unless a
means of producing sufficient surface contact is provided. In
addition, the fact that narrow tolerance ranges are difficult to
obtain for machined shapes comprising porous metal structures, such
as HEDROCEL, makes it likely that one will find gaps between the
adjacent surfaces of a porous layer placed against a metal
substrate.
[0035] One preferred means of ensuring that sufficient surface
contact is present is to provide a binding mixture between the
substrate and porous layer. The binding mixture fills in the porous
surface of the porous tantalum layer thereby "contouring" the
surface, and it fills in the "gaps" between the porous layer and
the substrate, thereby providing sufficient surface contact for
metallurgically bonding the porous tantalum layer and the metal
substrate.
[0036] Thus, referring again to FIG. 1, there is shown a Block 130
which represents providing a binding mixture. Generally, the
binding mixture of the present invention comprises an organic
binder with sufficient adhesive strength to hold a metal powder in
place. It is preferable to choose an organic binder that decomposes
within the temperate range of the diffusion bonding or sintering
step discussed subsequently herein. The organic binder may be
selected from the group consisting of gelatin, glycerin, polyvinyl
alcohol ("PVA") or a combination of the same. The binding mixture
further comprises powdered metal wherein the metal is preferably
the same as the metal used to form the metal substrate. However,
different metals that have good mutual solubility between the
substrate and the material comprising the porous layer may be used
in the binding mixture. For example, cobalt-chrome alloy, hafnium,
manganese, niobium, palladium, titanium-6, aluminum-4, vanadium
alloy, aluminum-7, titanium-nickel alloy, zirconium, zirconium
alloys, Ti-6Al-4V, Ti-6Al-7Nb, commercially pure titanium, titanium
alloys, and cobalt-chromium-molybdenum.
[0037] The binding mixture preferably comprises about 68% by volume
powdered metal and about 32% by volume of a solution comprising 10%
PVA and 90% water. However the binding mixture may comprise between
above about 10% by volume powdered metal and about 95% by volume
powdered metal. Exemplary binding mixture configurations are shown
in the EXAMPLES section of this application.
[0038] Referring still to FIG. 1 there is shown in Block 140,
representing the step of applying the binding mixture to the porous
layer. In the preferred embodiment, the binding mixture is applied
to the porous layer, and for clarity of explanation, the present
invention is described as having the binding mixture applied to the
porous layer. However, it is to be appreciated that the binding
mixture can also be applied to the substrate, depending on the
shape of the components that one desires to bond and the viscosity
of a chosen binding mixture. In any event, it is desirable to apply
the binding mixture as evenly as possible. Preferably, the binding
mixture is sprayed onto the porous layer, but the porous layer may
also be dipped into the binding mixture, or the binding mixture may
be painted on porous layer. Alternatively, the same techniques may
be used to apply the binding mixture to the substrate. An example
of a technique for applying a binding mixture is illustrated in
U.S. Pat. No. 5,198,308, assigned to the assignee of the present
application, and whose subject matter is hereby incorporated by
reference into the present application.
[0039] Referring again to FIG. 1, there is shown Block 150, which
represents the step of assembling the substrate and the porous
metal layer such that the binding mixture is disposed therebetween.
This step may be accomplished by any desirable means known in the
art whereby a first component is placed against a second
component.
[0040] Referring again to FIG. 1 there is shown in Block 160, which
represents the step of heating the assembly, to complete the
bonding process. In a preferred embodiment, the heating step
comprises: heating the assembly in a debinding cycle to a
temperature of within about 100.degree. C. to about 600.degree. C.
preferably in an inert atmosphere consisting essentially of argon
or helium having at most trace amounts of oxygen or nitrogen.
Alternatively, the heating step may be conducted in a partial
vacuum environment having a pressure of 0.01 torr or less. The
assembly is held at this temperature for about 1 hour to about 4
hours to remove the organic binder contained in the binding
mixture. A sintering cycle is then run at about 800.degree. C. to
1600.degree. C. for about 1 to 4 hours.
[0041] Referring now to FIG. 2, there is shown an alternative
embodiment of the present invention, comprising the steps of
providing a metal substrate, Block 210; providing a porous tantalum
layer, Block 220; providing a binding mixture, Block 230; applying
the binding mixture to the substrate, Block 240; assembling the
parts, Block 250; and applying heat and pressure to the assembly,
Block 260.
[0042] In the alternative embodiment shown in FIG. 2, the steps are
largely as described above; however, the step of applying heat and
pressure, shown in Block 260, comprises: heating the assembly to
within a temperature of within about 100.degree. C. to about
600.degree. C., preferably in an inert or partial vacuum
environment, and under a clamping pressure of between 200 and 1200
p.s.i. The clamping pressure is useful in assuring suitable surface
contact between the substrate and porous layer. Also, the heating
temperature required to achieve a particular bond strength between
the porous component and substrate is generally inversely
proportional to the amount of clamping pressure used. The assembly
is held at the desired temperature and pressure for about 1 hour to
about 4 hours.
[0043] In FIG. 3, there is shown another embodiment of the present
invention comprising the steps of: providing a metal substrate,
Block 310; providing a porous tantalum layer, Block 320; contouring
the surface of the porous metal layer, Block 330; assembling the
parts, Block 340; and applying heat and/or pressure to the
assembly, Block 350.
[0044] In the embodiment of FIG. 3, the steps of providing a metal
substrate, Block 310; and providing a tantalum porous layer, Block
320 are the same as described previously herein with regard to the
embodiment of FIG. 1. However, in this third embodiment of the
present invention, no binding mixture is used to enable the porous
tantalum layer to have adequate surface contact with the substrate.
Instead, an alternative means is used to contour the porous
tantalum layer to ensure that sufficient surface contact exists
between the components of the assembly. Specifically, as
represented by Block 330, the surface of the porous layer is
mechanically contoured or smeared to provide more surface contact
with the substrate. Generally, machining methods well known in the
art are used to contour the surface of the porous tantalum layer a
desirable amount. Alternatively, electro discharge machining may be
used to contour the surface of the porous tantalum layer.
[0045] Referring still to FIG. 3, the substrate and porous layer
are assembled as shown in Block 340, and heat and/or pressure are
applied to the assembly as shown in Block 350. The step of Block
350 comprises: heating the assembly to within a temperature of
within about 800.degree. C. to about 1600.degree. C. in a low
oxygen or partial vacuum environment. A clamping pressure may be
used if desired. The assembly is held at this temperature and
pressure for about 1 hour to about 4 hours.
[0046] Those skilled in the art will appreciate that for each
embodiment of the invention the times, temperatures, and pressures
may be manipulated to vary the bond strength between the porous
layer and the substrate and to vary the effects of the process on
the mechanical properties of the porous layer and the substrate. In
addition, the multiple cycles of applying heat and/or pressure may
used to similarly affect the strength of bond between components or
the mechanical properties of the substrate or porous layer.
[0047] While this invention has been described as having a
preferred design, the present invention can be further modified
within the spirit and scope of this disclosure. This application is
therefore intended to cover any variations, uses, or adaptations of
the invention using its general principles. Further, this
application is intended to cover such departures from the present
disclosure as come within known or customary practice in the art to
which this invention pertains and which fall within the limits of
the appended claims or their equivalents.
EXAMPLES
[0048]
1 SUBSTRATE POROUS CYCLE CYCLE CLAMPING BINDING MATERIAL LAYER
TEMPERATURE TIME ENVIRONMENT PRESSURE MIXTURE Ti-6AL-V HEDROCEL
955.degree. C. 2 cycles at Argon 400 p.s.i. 68% PVA + 4 hours 32%
(10% each PVA, 90% water solution) Ti-6AL-V HEDROCEL 955.degree. C.
2 cycles at Helium 400 p.s.i. 68% PVA + 4 hours 32% (10% each PVA,
90% water solution) Ti-6AL-V HEDROCEL 955.degree. C. 2 cycles at
Argon 400 p.s.i. N/A 4 hours each Ti-6AL-V Machined 350.degree. C.
3 hours 0.01 Torr N/A 68% PVA + HEDROCEL (debind) + (debind) + 32%
(10% 1200.degree. C. 4 hours PVA, 90% (sintering) (sintering) water
solution) Co--Cr--Mo Machined 1094.degree. C. 2 cycles at 0.01 Torr
400 p.s.i. 68% PVA + HEDROCEL 4 hours 32% (10% each PVA, 90% water
solution)
* * * * *