U.S. patent application number 13/624423 was filed with the patent office on 2013-03-28 for system for fabricating silicon carbide assemblies.
This patent application is currently assigned to EDISON WELDING INSTITUTE, INC.. The applicant listed for this patent is Nathan D. AMES, Kirk E. COOPER, Edward D. HERDERICK. Invention is credited to Nathan D. AMES, Kirk E. COOPER, Edward D. HERDERICK.
Application Number | 20130075039 13/624423 |
Document ID | / |
Family ID | 47909940 |
Filed Date | 2013-03-28 |
United States Patent
Application |
20130075039 |
Kind Code |
A1 |
HERDERICK; Edward D. ; et
al. |
March 28, 2013 |
SYSTEM FOR FABRICATING SILICON CARBIDE ASSEMBLIES
Abstract
A system for fabricating silicon carbide assemblies that
includes at least two silicon carbide materials; at least one
joining interlayer positioned between the at least two silicon
carbide materials, wherein the at least one joining interlayer
further includes a first material that melts at a first temperature
and a second material interspersed throughout the first material,
and wherein the second material melts at a temperature that is
lower than that of the first material; and at least one apparatus
for applying energy to the joining interlayer, wherein applying
energy to the joining interlayer is operative to soften the first
material and melt the second material, and wherein softening the
first material and melting the second material is operative to
transform the joining interlayer into a substantially porosity-free
adherent material capable of joining together the at least two
silicon carbide materials.
Inventors: |
HERDERICK; Edward D.;
(Powell, OH) ; COOPER; Kirk E.; (Worthington,
OH) ; AMES; Nathan D.; (Sunbury, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HERDERICK; Edward D.
COOPER; Kirk E.
AMES; Nathan D. |
Powell
Worthington
Sunbury |
OH
OH
OH |
US
US
US |
|
|
Assignee: |
EDISON WELDING INSTITUTE,
INC.
Columbus
OH
|
Family ID: |
47909940 |
Appl. No.: |
13/624423 |
Filed: |
September 21, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61538409 |
Sep 23, 2011 |
|
|
|
Current U.S.
Class: |
156/379.6 ;
156/349; 219/121.63; 228/41 |
Current CPC
Class: |
C04B 35/565 20130101;
C04B 2237/59 20130101; B32B 37/06 20130101; C04B 37/026 20130101;
C04B 2237/72 20130101; C04B 2237/365 20130101; B23K 1/0056
20130101; C04B 37/006 20130101; C04B 2237/40 20130101; C04B
2237/595 20130101; G21C 3/07 20130101; C04B 2235/3826 20130101;
C22C 21/02 20130101; B23K 37/00 20130101; Y02E 30/30 20130101; C04B
2237/60 20130101; C04B 2237/403 20130101; B23K 1/008 20130101; Y02E
30/40 20130101; B32B 37/00 20130101; B23K 26/20 20130101; C04B
2237/121 20130101 |
Class at
Publication: |
156/379.6 ;
156/349; 228/41; 219/121.63 |
International
Class: |
B32B 37/00 20060101
B32B037/00; B23K 37/00 20060101 B23K037/00; B23K 26/20 20060101
B23K026/20; B32B 37/06 20060101 B32B037/06 |
Claims
1) A system for fabricating assemblies, comprising: (a) at least
two components for forming an assembly, wherein the at least two
components further include ceramic, metal, or composite, and
wherein the assembly further includes ceramic and metal; metal and
metal; composite and metal; or composite and composite; (b) at
least one joining interlayer positioned between the at least two
components, wherein the at least one joining interlayer further
includes a first material that melts at a first temperature and a
second material interspersed throughout the first material, and
wherein the second material melts at a second temperature that is
lower than that of the first material; and (c) at least one
apparatus for applying energy to the joining interlayer, wherein
applying energy to the joining interlayer is operative to soften
the first material and melt the second material, and wherein
softening the first material and melting the second material is
operative to transform the joining interlayer into a substantially
porosity-free adherent material capable of joining together the at
least two components.
2) The system of claim 1, wherein the joining interlayer further
comprises aluminum and silicon.
3) The system of claim 1, wherein the joining interlayer further
comprises a multi-phase hypereutectic Al-80 wt % Si alloy.
4) The system of claim 1, wherein the joining interlayer further
comprises a high-temperature metal layer sandwiched between two
multiphase alloy joining layers.
5) The system of claim 1, wherein the high-temperature metal layer
sandwiched between two multiphase alloy joining layers further
includes titanium, zirconium, molybdenum, niobium, or combinations
thereof
6) The system of claim 1, wherein the at least one apparatus for
applying energy to the joining interlayer is a furnace.
7) The system of claim 1, wherein the at least one apparatus for
applying energy to the joining interlayer is a laser.
8) The system of claim 1, wherein the at least one apparatus for
applying energy to the joining interlayer creates heat at
temperatures between about 725.degree. C. and about 1450.degree.
C.
9) A system for fabricating silicon carbide assemblies, comprising:
(a) at least two silicon carbide materials; (b) at least one
joining interlayer positioned between the at least two silicon
carbide materials, wherein the at least one joining interlayer
further includes a first material that melts at a first temperature
and a second material interspersed throughout the first material,
and wherein the second material melts at a second temperature that
is lower than that of the first material; and (c) at least one
apparatus for heating the joining interlayer to a predetermined
temperature, wherein heating the joining interlayer to the
predetermined temperature is operative to soften the first material
and melt the second material, and wherein softening the first
material and melting the second material is operative to transform
the joining interlayer into a substantially porosity-free adherent
material capable of joining together the at least two silicon
carbide materials.
10) The system of claim 9, wherein the joining interlayer further
comprises aluminum and silicon.
11) The system of claim 9, wherein the joining interlayer further
comprises a multi-phase hypereutectic Al-80 wt % Si alloy.
12) The system of claim 9, wherein the joining interlayer further
comprises a high-temperature metal layer sandwiched between two
multiphase alloy joining layers.
13) The system of claim 12, wherein the high-temperature metal
layer sandwiched between two multiphase alloy joining layers
further includes titanium, zirconium, molybdenum, niobium, or
combinations thereof.
14) The system of claim 9, wherein the at least one apparatus for
heating the joining interlayer is a furnace.
15) The system of claim 9, wherein the at least one apparatus for
heating the joining interlayer is a laser.
16) The system of claim 9, wherein the at least one apparatus
heating the joining interlayer creates heat at temperatures between
about 725.degree. C. and about 1450.degree. C.
17) A system for fabricating silicon carbide assemblies,
comprising: (a) at least two silicon carbide materials; (b) at
least one hypereutectic aluminum-silicon alloy joining interlayer
positioned between the at least two silicon carbide materials,
wherein the silicon melts at a first temperature, and wherein the
aluminum melts at a second temperature that is lower than that of
the silicon; and (c) at least one apparatus for heating the joining
interlayer to a predetermined temperature, wherein heating the
joining interlayer to the predetermined temperature is operative to
soften the silicon and melt the aluminum, and wherein softening the
silicon and melting the aluminum is operative to transform the
joining interlayer into a substantially porosity-free adherent
material capable of joining together the at least two silicon
carbide materials.
18) The system of claim 17, wherein the at least one apparatus for
heating the joining interlayer is a furnace.
19) The system of claim 17, wherein the at least one apparatus for
heating the joining interlayer is a laser.
20) The system of claim 17, wherein the at least one apparatus
heating the joining interlayer creates heat at temperatures between
about 725.degree. C. and about 1450.degree. C.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This patent application claims the benefit of U.S.
Provisional Patent Application Ser. No. 61/538,409 filed on Sep.
23, 2011 and entitled "Method for Joining Ceramic Bodies to One
Another," the disclosure of which is hereby incorporated by
reference herein in its entirety and made part of the present U.S.
utility patent application for all purposes.
BACKGROUND OF THE INVENTION
[0002] The present invention relates generally to methods for
joining structural and functional ceramic bodies to one another,
and more specifically to a system and method for joining silicon
carbide to itself using melting point assisted multiphase brazing
so that the joined silicon carbide may be used, for example, as
fuel cladding in nuclear reactors.
[0003] Ceramic materials are useful for certain demanding
engineering applications due to their: (i) excellent strength at
high temperature; (ii) resistance to chemical attack; (iii)
inertness in radiation environments; and (iv) certain functional
characteristics including optical properties, semiconductor
properties and piezoelectricity. However, ceramics are not easily
fabricated into complex shapes and, as a consequence, require
advanced joining processes to integrate such materials into useful
products. Joining silicon carbide to itself or other materials
(e.g., other engineering ceramics, metals) is important for
applications including manufacturing personal and vehicle armor,
gas turbine engines, air breathing rocket engines, fusion reactors,
and high temperature electronics. For use in the nuclear industry,
various approaches have been investigated for joining silicon
carbide to itself However, these approaches have not been
successful in addressing radiation damage and retaining joint
integrity after irradiation.
[0004] Using silicon carbide (SiC) ceramic-matrix composites as the
fuel cladding in light water reactors could lead to a very
significant increase in the safety of existing reactors and
transitioning from zirconium alloy nuclear fuel cladding to a
silicon carbide composite cladding represents a significant shift
in light water reactor materials technology. SiC is an important
structural ceramic material owing to its excellent thermal and
environmental stability, resistance to radiation, resistance to
thermal shock, and high strength and toughness. Additionally, SiC
is stable at temperatures in excess of 2,000.degree. C. and does
not melt under loss of coolant accident (LOCA) conditions.
Furthermore, SiC does not suffer from fretting wear and produces
very small amounts of hydrogen during oxidation in high temperature
steam relative to presently used Zirconium alloys.
[0005] In addition to potentially improving safety, SiC has a lower
neutron penalty than Zircaloy and may provide economic benefits if
the same thickness of material is used in newly designed cladding.
This may also allow for higher fuel burnups, thereby reducing the
amount of nuclear fuel used by a reactor. Accordingly, SiC fuel
cladding is considered to be an important strategic technology for
advanced nuclear fuels programs. However, joining end plugs to
cladding tubes for sealing in fuel pellets once they have been
loaded into the fuel rods represents a remaining technical hurdle.
This is an inherently difficult problem and acceptable technical
solutions must be based on in-reactor conditions. Desired joint
characteristics include mechanical robustness in commercial nuclear
reactor conditions of 2250 PSI, at 350.degree. C., in a water/steam
environment, at neutron flux rate of about 1.times.10.sup.14
n/cm.sup.2-s (thermal+fast), for more than 6 years of service, and
closure of the rod should be maintainable at temperatures of up to
1200.degree. C.
[0006] Known technical approaches for joining SiC for use in
nuclear environments include glass-ceramic bonding, displacement
reaction bonding using Ti.sub.3SiC.sub.2, diffusion bonding with
metallic foil inserts, and brazing using silicon containing
materials. None of these approaches results in a product that can
survive irradiation and flowing water tests that mimic in-service
reactor conditions. Furthermore, these approaches require high
pressures or extensive heating times to form mechanically sound
joints, thereby making manufacturing difficult. Therefore, there is
an ongoing need for a system and/or method that effectively joins
silicon carbide to itself or to other materials to create
assemblies for use in a variety of applications including fuel
cladding in nuclear reactors.
SUMMARY OF THE INVENTION
[0007] The following provides a summary of certain exemplary
embodiments of the present invention. This summary is not an
extensive overview and is not intended to identify key or critical
aspects or elements of the present invention or to delineate its
scope.
[0008] In accordance with one aspect of the present invention, a
first system for fabricating assemblies is provided. This system
includes at least two components for forming an assembly, wherein
the at least two components further include ceramic, metal, or
composite, and wherein the assembly further includes ceramic and
metal; metal and metal; composite and metal; or composite and
composite; at least one joining interlayer positioned between the
at least two components, wherein the at least one joining
interlayer further includes a first material that melts at a first
temperature and a second material interspersed throughout the first
material, and wherein the second material melts at a second
temperature that is lower than that of the first material; and at
least one apparatus for applying energy to the joining interlayer,
wherein applying energy to the joining interlayer is operative to
soften the first material and melt the second material, and wherein
softening the first material and melting the second material is
operative to transform the joining interlayer into a substantially
porosity-free adherent material capable of joining together the at
least two components.
[0009] In accordance with another aspect of the present invention,
a second system for fabricating silicon carbide assemblies is
provided. This system includes at least two silicon carbide
materials; at least one joining interlayer positioned between the
at least two silicon carbide materials, wherein the at least one
joining interlayer further includes a first material that melts at
a first temperature and a second material interspersed throughout
the first material, and wherein the second material melts at a
second temperature that is lower than that of the first material;
and at least one apparatus for heating the joining interlayer to a
predetermined temperature, wherein heating the joining interlayer
to the predetermined temperature is operative to soften the first
material and melt the second material, and wherein softening the
first material and melting the second material is operative to
transform the joining interlayer into a substantially porosity-free
adherent material capable of joining together the at least two
silicon carbide materials.
[0010] In yet another aspect of this invention, a third system for
fabricating silicon carbide assemblies is provided. This system
includes at least two silicon carbide materials; at least one
hypereutectic aluminum-silicon alloy joining interlayer positioned
between the at least two silicon carbide materials, wherein the
silicon melts at a first temperature, and wherein the aluminum
melts at a second temperature that is lower than that of the
silicon; and at least one apparatus for heating the joining
interlayer to a predetermined temperature, wherein heating the
joining interlayer to the predetermined temperature is operative to
soften the silicon and melt the aluminum, and wherein softening the
silicon and melting the aluminum is operative to transform the
joining interlayer into a substantially porosity-free adherent
material capable of joining together the at least two silicon
carbide materials.
[0011] Additional features and aspects of the present invention
will become apparent to those of ordinary skill in the art upon
reading and understanding the following detailed description of the
exemplary embodiments. As will be appreciated by the skilled
artisan, further embodiments of the invention are possible without
departing from the scope and spirit of the invention. Accordingly,
the drawings and associated descriptions are to be regarded as
illustrative and not restrictive in nature.
DESCRIPTION OF THE FIGURES
[0012] The accompanying drawings, which are incorporated into and
form a part of the specification, schematically illustrate one or
more exemplary embodiments of the invention and, together with the
description given below, serve to explain the principles of the
invention, and wherein:
[0013] FIG. 1 is a highly simplified illustration of an exemplary
embodiment of the present invention wherein a ceramic body has been
joined to either a ceramic or metallic body using a single joining
interlayer;
[0014] FIG. 2 is a highly simplified illustration of an exemplary
embodiment of the present invention wherein a ceramic body has been
joined to either a ceramic or metallic body using a high
temperature metal interlayer and two joining interlayers; and
[0015] FIG. 3 is a highly simplified illustration of an exemplary
silicon carbide assembly fabricated in accordance with the present
invention, wherein the "ligaments" formed by the material that
melts at the lower of the two melting temperature are visible in
the assembly.
DETAILED DESCRIPTION OF THE INVENTION
[0016] Exemplary embodiments of the present invention are now
described with reference to the Figures. Although the following
detailed description contains many specifics for purposes of
illustration, a person of ordinary skill in the art will appreciate
that many variations and alterations to the following details are
within the scope of the invention. Accordingly, the following
embodiments of the invention are set forth without any loss of
generality to, and without imposing limitations upon, the claimed
invention.
[0017] As previously stated, the present invention relates
generally to a system and method for joining structural and
functional ceramics to one another or to other materials and more
specifically to a system for joining silicon carbide to itself for
use as nuclear fuel cladding. SiC-based fuel cladding is currently
the most promising technology for enhanced accident-tolerant
nuclear fuel cladding and this system utilizes a two or more phase
joining interlayer that further includes at least one phase that
has a higher melting point than the second or other phases. During
processing, the higher melting point phase remains in a solid or
semi-solid state and is compressed due to applied pressure. The
lower melting point phase or phases melt and segregate to the
boundaries of the higher melting point phase. This process assists
in the wetting of the higher melting point phase and bonding it to
the surfaces of substrate materials, thereby resulting in the
formation of a two or more phase joint microstructure that provides
improved toughness for preventing crack formation during processing
and service. This approach has proven to create a robust joint that
is made of materials with low radiation sensitivity and that is
likely to withstand radiation damage. With reference now to the
Figures, one or more exemplary embodiments of this invention shall
be described in greater detail.
[0018] With reference to FIGS. 1-3, the present invention provides
a system and method for fabricating silicon carbide assemblies 10
by joining ceramic bodies to one another (or to metallic bodies)
using melting point-assisted multiphase brazing. This system
typically includes at least two silicon carbide materials (12 and
14); at least one joining interlayer 16 positioned between the at
least two silicon carbide materials, wherein the at least one
joining interlayer further includes a first material that melts at
a first temperature and a second material interspersed throughout
the first material, and wherein the second material melts at a
temperature that is lower than that of the first material; and at
least one apparatus for applying energy to the joining interlayer,
wherein applying energy to the joining interlayer is operative to
soften the first material and melt the second material, and wherein
softening the first material and melting the second material is
operative to transform the joining interlayer into a substantially
porosity-free adherent material capable of joining together the at
least two silicon carbide materials.
[0019] In one embodiment of this invention, the joining interlayer
includes primarily silicon and aluminum with small amounts of one
or more alloying elements. These two-phase hypereutectic
(Si>12.2 wt %) Al--Si alloys are unique due to their "divorced
eutectic" microstructure that consists of pure aluminum
interspersed in pure silicon which results in the unique
microstructure of the final joined assembly. In this embodiment,
the apparatus for applying energy to the joining interlayer may be
a furnace heating source in a vacuum or partial pressure argon
atmosphere or, alternately, a laser heating source. Other suitable
heating sources may be used with this invention. Multiple Al-Si
alloys may be processed over a range of temperatures and times
using such heating sources. For example, in one embodiment, Al-80
wt % Si alloy is processed in a vacuum at about 1330.degree. C. for
about 13 minutes for joining Hexoloy.RTM. SA silicon carbide blocks
(Saint-Gobain Ceramics; Niagara Falls, N.Y.) to one another (see
FIG. 1). Another exemplary embodiment utilizes two lower-melting
point Al-12 wt % Si joining interlayers and an Al-70 wt % Si
higher-temperature melting interlayer. Alternately, the embodiment
shown in FIG. 2 may utilize two Al-80 wt % Si alloy sheets 16 as
the joining interlayers. These Al-80 wt % Si alloy sheets are
placed on either side of a higher-melting temperature metal layer
17 such as titanium or zirconium or refractory metals such as
molybdenum or niobium or alloys thereof and then processed in a
vacuum at about 1330.degree. C. for about 13 minutes for joining
Hexoloy.TM. SA silicon carbide to itself. The higher-melting
temperature metal interlayer in this embodiment would not typically
melt during the processing, but would provide strain tolerance
where joined ceramic bodies might swell or expand at rates
different than the joining interlayer.
[0020] In general, the present invention can be used to join
silicon carbide to itself using applied temperatures of between
725.degree. C. and 1450.degree. C. The lower melting temperature
aluminum melts at boundaries between non-melted silicon areas and
may assist in diffusion bonding under low applied loads of several
pounds. Other materials combinations including silicide compounds
such as niobium silicide or titanium silicide may be used as the
higher melting temperature phase. Another exemplary embodiment
includes the formation of a silicon nitride joining interlayer
between the joined bodies by heating the joined assembly in a
nitrogen atmosphere consisting of a ceramic, ceramic or metallic
body, and an Al--Si joining interlayer. By heating above
approximately 1100.degree. C. up to 1450.degree. C. in high-purity
nitrogen for at least 5 minutes and up to several hours, the Al
reacts to form aluminum nitride and the silicon reacts to form
silicon nitride. Using this method, the melting point of the
joining interlayer is significantly increased by a simple
post-joining thermal treatment in a controlled atmosphere. The
system of this invention may be used with monolithic components or
composites such as those including fiber in their structure.
[0021] Shear strength testing on the joints of silicon carbide
assemblies fabricated in accordance with the present invention
demonstrated shear strengths in excess of 125 MPa. Joined
assemblies were also subjected to temperature cycling tests by
cycling the assemblies in air 25X between 20.degree. C. and
350.degree. C. initially, then between 20.degree. C. to
1200.degree. C. Structural analysis of these assemblies using
optical and scanning electron microscopy showed no change in braze
joint microstructure and no crack formation as a result of thermal
cycling. Post cycling shear testing showed no loss of strength. An
assembly was also subjected to a water quench test in which it was
heated to 700.degree. C. and then quickly transferred to a water
quench bath. A crack started to form in the braze layer, but due to
the crack-arresting properties of the two-phase joining interlayer,
the assembly remained joined macroscopically as opposed to complete
debonding. Meeting the 1200.degree. C. temperature threshold for
joint integrity is particularly important as that is the
temperature stability target for a design basis reactor accident.
As shown in FIG. 3, the formation of lower melting point joining
structures resembling ligaments 18 contributes to the
crack-arresting properties of joining interlayer 16.
[0022] Silicon carbide assemblies made in accordance with the
present invention were also subjected to irradiation testing in a
research nuclear reactor PWR flow loop. Several joined assemblies
were irradiated in the typical PWR primary water conditions of
300.degree. C., 1000 ppm B and 7 ppm Li at saturation pressure.
These samples remained in the reactor for 6 months and accumulated
about 11,200 MWh in that period. Based on typical flux numbers for
the facility, this exposure corresponds to about
3.7.times.10.sup.20 n/cm.sup.2-s E>0.1 MeV. Even after this
length of time, joint integrity was retained in these samples.
[0023] An important aspect of the melting point assisted multiphase
diffusion brazing approach embodied by the present invention is
that this system provides a controlled neutron expansion material
brazing system. Under neutron irradiation, materials typically
undergo swelling due to atomic displacements; this swelling causes
stresses to build up in the joint. Therefore, systems must be
engineered that can accommodate these stresses in-service. The
composite joining system of this invention mitigates neutron
induced swelling and expansion and the exemplary embodiments
described herein include a two-phase system that expands under
neutron irradiation in a controlled manner. Thus, this system
maintains mechanical integrity under neutron irradiation.
Microstructural evaluation performed after joining showed a fully
dense microstructure that is likely to be hermetic through the
operating pressures experienced in a commercial operating nuclear
reactor. With regard to other advantages of this invention, the
described joining system does not require extensive heating times
or high pressures that may prove difficult and economically
impractical for manufacturing of production fuel rod cladding
assemblies. This process also allows for the integration of
mechanical features, such as threaded joints or pins, which would
extend the temperature stability of the full joining solution to
beyond design-basis accidents. The joining technology of this
invention may also incorporate mechanical interlocks to further
increase the safety factor of the fabricated assemblies.
[0024] While the present invention has been illustrated by the
description of exemplary embodiments thereof, and while the
embodiments have been described in certain detail, it is not the
intention of the Applicant to restrict or in any way limit the
scope of the appended claims to such detail. Additional advantages
and modifications will readily appear to those skilled in the art.
Therefore, the invention in its broader aspects is not limited to
any of the specific details, representative devices and methods,
and/or illustrative examples shown and described. Accordingly,
departures may be made from such details without departing from the
spirit or scope of the applicant's general inventive concept.
* * * * *