U.S. patent application number 15/681705 was filed with the patent office on 2017-11-30 for method for obtaining a configuration for joining a ceramic material to a metallic structure.
This patent application is currently assigned to ALSTOM TECHNOLOGY LTD.. The applicant listed for this patent is ALSTOM TECHNOLOGY LTD.. Invention is credited to Hans-Peter BOSSMANN, Matthias HOEBEL, Gregoire Etienne WITZ.
Application Number | 20170341339 15/681705 |
Document ID | / |
Family ID | 48142641 |
Filed Date | 2017-11-30 |
United States Patent
Application |
20170341339 |
Kind Code |
A1 |
HOEBEL; Matthias ; et
al. |
November 30, 2017 |
METHOD FOR OBTAINING A CONFIGURATION FOR JOINING A CERAMIC MATERIAL
TO A METALLIC STRUCTURE
Abstract
A configuration for joining a ceramic layer has a thermal
insulating material to a metallic layer. The configuration includes
an interface layer made of metallic material located between the
ceramic layer and the metallic layer, which includes a plurality of
interlocking elements on one of its sides, facing the ceramic
layer, the ceramic layer comprising a plurality of cavities aimed
at connecting with the corresponding interlocking elements of the
interface layer. The configuration also includes a brazing layer by
means of which the interface layer is joint to the metallic layer.
The invention also refers to a method for obtaining such a
configuration.
Inventors: |
HOEBEL; Matthias; (Windisch,
CH) ; BOSSMANN; Hans-Peter; (Lauchringen, DE)
; WITZ; Gregoire Etienne; (Birmenstorf, CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ALSTOM TECHNOLOGY LTD. |
Baden |
|
CH |
|
|
Assignee: |
ALSTOM TECHNOLOGY LTD.
Baden
CH
|
Family ID: |
48142641 |
Appl. No.: |
15/681705 |
Filed: |
August 21, 2017 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
14250665 |
Apr 11, 2014 |
9764530 |
|
|
15681705 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B23K 26/60 20151001;
F23R 3/007 20130101; B23K 2103/52 20180801; F23M 2900/05004
20130101; B23K 1/19 20130101; C04B 37/026 20130101; B23K 26/032
20130101; C04B 2235/945 20130101; C04B 2237/72 20130101; C04B
2237/592 20130101; C04B 2237/12 20130101; B32B 18/00 20130101; B23K
2103/172 20180801; C04B 2237/64 20130101; Y10T 428/12618 20150115;
B23K 26/342 20151001; B23K 26/32 20130101; C04B 2237/595 20130101;
B32B 7/08 20130101; B23K 26/211 20151001 |
International
Class: |
B32B 7/08 20060101
B32B007/08; B32B 18/00 20060101 B32B018/00; B23K 26/211 20140101
B23K026/211; B23K 26/342 20140101 B23K026/342; B23K 1/19 20060101
B23K001/19; B23K 26/03 20060101 B23K026/03; B23K 26/32 20140101
B23K026/32; C04B 37/02 20060101 C04B037/02; F23R 3/00 20060101
F23R003/00; B23K 26/60 20140101 B23K026/60 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 12, 2013 |
EP |
13163603.7 |
Claims
1. A material for joining a ceramic layer comprising a thermal
insulating material to a metallic layer, an interface layer made of
metallic material located between the ceramic layer and the
metallic layer, having a plurality of interlocking elements on one
of its sides, facing the ceramic layer, the ceramic layer including
a plurality of cavities aimed at connecting with the corresponding
interlocking elements of the interface layer, and a brazing layer
by means of which the interface layer is joint to the metallic
layer.
2. The material according to claim 1, wherein the plurality of
cavities in the ceramic layer are filled with metallic filler,
protruding from the ceramic layer, such that metallic struts are
formed.
3. The material according to claim 2, further comprising a defined
gap between the ceramic layer together with the interface layer,
with respect to the metallic layer, the cited gap being defined by
selecting the length of the interlocking elements to define the
metallic struts between the ceramic layer and the interface
layer.
4. The material according to claim 1, wherein the interface layer
comprises a plurality of near wall cooling channels, the ceramic
layer and the interface layer with the cooling channels being
further brazed to the metallic layer.
5.-14. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to European application
13163603.7 filed Apr. 12, 2013, the contents of which are hereby
incorporated in its entirety.
TECHNICAL FIELD
[0002] The present invention relates to a configuration for joining
a ceramic thermal insulating material to a metallic structure,
preferably used in hot gas environments. The invention also refers
to a method for obtaining such a configuration.
BACKGROUND
[0003] When operating in hot gas environments, joining a ceramic
thermal insulating material to a metallic structure requires a good
control of the stress level in the ceramic thermal insulating
material in order to avoid premature failure of the ceramic
material. In order to achieve this, it is interesting to design the
joint of the ceramic material and metallic material for the highest
possible temperature, in order to minimize the required thickness
of the ceramic thermal insulating material, such that the thermal
stresses in such ceramic material part are reduced, as they are
directly related to the temperature gradient on said part. The
benefit of a high temperature joint on the thermal gradient in the
ceramic layer is counterbalanced by a higher stress level at the
joint due to the difference of thermal expansion coefficients of
the ceramic and of the metallic substrate. Besides, the higher the
temperature of the metallic material during operation, the higher
the oxidation rate of the metallic material will be; therefore, the
metallic material composing the joint needs to have a high
oxidation resistance.
[0004] It is known in the state of the art to join a ceramic
thermal insulating material to a metallic structure by means of
brazing of the ceramic part to the metallic part, using active
brazing, reactive air brazing or metallization of the ceramic
material. However, all these known solutions are limited in
temperature capability, either due to the low melting point of the
active braze alloys that are used (based on Ag or Au) when active
or reactive air brazing is used, or due to the poor oxidation
resistance of the metal used when metallization of the ceramic
material is done, this metal used for metallization being typically
Mo or Mn.
[0005] Another possibility known in the art is to join the ceramic
material and the metallic material by means of mechanical joining:
this solution allows the selection of the materials to be used
specifically for their functional properties with minimum
constraints on materials compatibility. However, when a mechanical
joining solution is used, the problem is that stress concentration
occurs at the joining location, which leads to a local risk of
cracking of the ceramic material, which can propagate
catastrophically through the whole ceramic material, leading to its
premature failure.
[0006] Other solutions known in the art are, for example, fitting
the ceramic in a metallic clamping system, having the problems as
described for the mechanical joining stated above, or using high
temperature cements, presenting the problem of a brittle joining
layer with limited mechanical properties subjected to high stress
levels, leading to possible local cracking that can propagate and
cause a premature failure of the ceramic material.
[0007] The present invention is directed towards providing a
joining configuration that solves the above-mentioned problems in
the prior art.
SUMMARY
[0008] According to a first aspect, the present invention relates
to a configuration for joining a ceramic layer comprising a thermal
insulating material to a metallic layer, the configuration being
used in hot gas environments. The configuration of the invention
comprises an interface layer made of metallic material, located
between the ceramic layer and the metallic layer, comprising a
plurality of interlocking elements on one of its sides, facing the
ceramic layer. According to the configuration of the invention, the
ceramic layer comprises a plurality of cavities aimed at connecting
with the corresponding interlocking elements of the interface
layer. The configuration of the invention also comprises a brazing
layer, by means of which the interface layer is joint to the
metallic layer.
[0009] The invention also refers to a method for obtaining a
configuration as the one described above. The method of the
invention configures the interface layer comprising a plurality of
interlocking elements on one of its sides, facing the ceramic
layer, by means of a laser metal forming process.
BRIEF DESCRIPTION OF DRAWINGS
[0010] The foregoing objects and many of the attendant advantages
of this invention will become more readily appreciated as the same
becomes better understood by reference to the following detailed
description when taken in conjunction with the accompanying
drawings, wherein.
[0011] FIG. 1 shows a schematic view of the ceramic layer in the
configuration for joining a ceramic layer comprising a thermal
insulating material to a metallic layer according to the present
invention.
[0012] FIG. 2 shows a schematic view of the ceramic and the
interface layer in the configuration for joining a ceramic layer
comprising a thermal insulating material to a metallic layer
according to the present invention.
[0013] FIG. 3 shows a schematic view of the in the configuration
for joining a ceramic layer comprising a thermal insulating
material to a metallic layer according to a first embodiment of the
present invention.
[0014] FIG. 4 shows a schematic view of the in the configuration
for joining a ceramic layer comprising a thermal insulating
material to a metallic layer according to a second embodiment of
the present invention.
[0015] FIG. 5 shows a schematic view of the in the configuration
for joining a ceramic layer comprising a thermal insulating
material to a metallic layer according to a third embodiment of the
present invention.
[0016] FIG. 6 shows a schematic view of the method of the
invention, for configuring the interface layer in the configuration
for joining a ceramic layer comprising a thermal insulating
material to a metallic layer according to the present
invention.
[0017] FIG. 7 shows a schematic view of the in the configuration
for joining a ceramic layer comprising a thermal insulating
material to a metallic layer according to a fourth embodiment of
the present invention.
DETAILED DESCRIPTION
[0018] According to a first aspect, the present invention relates
to a configuration 10 for joining a ceramic layer 1 comprising a
thermal insulating material to a metallic layer 2, the
configuration 10 being used in hot gas environments, typically in
gas turbine environments. The configuration 10 comprises an
interface layer 11 made of metallic material, located between the
ceramic layer 1 and the metallic layer 2, comprising a plurality of
interlocking elements 20 on one of its sides, facing the ceramic
layer 1. According to the configuration of the invention, the
ceramic layer 1 comprises a plurality of cavities 30 aimed at
connecting with the corresponding interlocking elements 20 of the
interface layer 11. The configuration 10 of the invention also
comprises a brazing layer 40, by means of which the interface layer
11 is joint to the metallic layer 2.
[0019] The invention also refers to a method for obtaining a
configuration 10 as the one described above. The method of the
invention configures the interface layer 11 comprising a plurality
of interlocking elements 20 on one of its sides, facing the ceramic
layer 1, by means of a laser metal forming process, as it will be
further explained.
[0020] In order to reduce the stress concentration at the joining
location, a robust joining design with the configuration 10 of the
invention is proposed, having a high number of joining contacts
(interlocking elements 20 and cavities 30); besides, the geometry
of the joints is such as to reduce the residual stresses. In order
to achieve this, the ceramic layer 1 is manufactured such as to
have cavities 30 in itself (see FIG. 1) and the interface layer 11
is then manufactured to fill these cavities 30, leading to an
interlocking between the ceramic layer 1 and the interface layer
11. The manufacturing of the interface layer 11 has therefore to be
accurately adapted to the shape of each one of the cavities 30 in
the ceramic layer 1. This can be achieved in several possible ways:
[0021] 1) The ceramic layer 1 is directly produced with cavities 30
including interlocking features such as overhangs 3. Each part that
is produced is scanned with a suitable optical device, for example
a 3D photogrammetric scanner and a reference position of each one
of the cavities 30 is saved in a data file together with an
identification number corresponding to the number of the part. In a
second step, an automated laser metal forming operation is
performed, where a powder nozzle 4 being fed with powder and gas 6
is positioned at the reference positions where the interlocking
elements 20 have to be located, the powder being locally re-molten
with a focus laser beam 5, allowing the locally molten metallic
powder to fill the cavities produced, as shown in FIG. 6. The
positioning of the powder nozzle 4 can be made either with a robot
or with a CNC (computer numerical control). [0022] 2) Another
possibility is to make a first step in which a short pulse laser
machining operation is performed to create the cavities 30 on the
surface of the ceramic layer 1. Preferably, ns or ps pulses are
chosen to create clean cavities 30 free of melt and without crack
formation in the ceramic layer 1. The second step is similar to the
one described already in 1) above: however, no scanning is
necessary because the previous machining positions can be directly
used as target positions for the laser metal forming step.
[0023] Using one of the two methods described above, a variety of
shapes can be created as interlocking elements 20, as shown in
different embodiments of the invention, shown on FIGS. 3 to 7.
Depending on the required strength of the joint and the functional
requirements of the configuration 10, number and density and the
degree of coverage of the ceramic layer 1 by interlocking elements
20 can be tailored. Another possibility is to have the cavities 30
filled with metal so that the metallic filler protrudes from the
ceramic layer 1 forming metallic struts. With an additional
grinding or milling operation, a defined offset between the
surfaces of the ceramic layer 1 together with the interface layer
11 with respect to the metallic layer 2 can be produced avoiding
premature failure due to the reduced stress level at the points of
contacts between the ceramic layer 1 and the metallic filler due to
the low stiffness of the metallic struts.
[0024] The laser metal forming material is very flexible with
respect to the filler material, preferably the metallic filler
material. As an example, high temperature Ni-based braze powders
with high service temperature capability and good oxidation
resistance, such as the commercially available braze alloys Amdry
915 or Amdry 103 can be chosen as the filler material. Because the
laser/powder nozzle 4 or the ceramic layer 1 can be tilted, there
is a high flexibility with respect to the shapes of the
interlocking elements 20.
[0025] As an alternative (see FIG. 1), a powder blend of high
strength superalloy and high temperature braze material can be
used. In both cases, the ceramic layer 1 interlocking with the
interface layer 11 can be directly joined to the metallic layer 2
acting as carrier structure. If a defined offset between the two
surfaces (ceramic layer 1 together with interface layer 11 and
metallic layer 2) needs to be ensured, a super solidus brazing of
the ceramic layer 1 and interface layer 11 together with the
metallic layer 2 can be envisaged. In this case, the brazing
temperature is set at an intermediate value between the filler
alloy's solid and liquid temperature. As a consequence, only a
small fraction of the filler is molten and the metallic joints
(interlocking elements 20) maintain their shape ensuring the
correct offset between the ceramic layer 1 together with interface
layer 11 and metallic layer 2.
[0026] As a preferred embodiment (see FIG. 2, 3, 4, 5 or 7), a
superalloy with high temperature capability is used as the filler
material. Depending on the local requirements, materials with
superior oxidation resistance, corrosion resistance, excellent
mechanical strength, or a suitable combination of these properties
can be chosen like Amdry 995, Amdry 963, Haynes 230 or Inconel 738.
In this case, an additional brazing layer 40 has to be applied
between the metallic layer 2 and the ceramic layer 1 joined to the
interface layer 11. However, the high area coverage of the ceramic
layer 1 with the interface layer 11 greatly improves the
wettability and makes the brazing much more reliable. Therefore,
the flexibility with respect to the brazing material used to
configure the brazing layer 40 is higher and high temperature braze
foils with much higher service temperature can be chosen. A defined
gap can be built by selecting the length of the interlocking
elements 20 such to define metallic struts between the ceramic
layer 1 and the interface layer 11. These struts have a low
stiffness and can be designed such that the stress level at the
points of contacts between the interlocking elements 20 and the
ceramic layer 1 is low enough to avoid crack formation and crack
growth in the ceramic layer 1 either at room temperature or during
service.
[0027] In all cases, excessive heat input to the ceramic layer 1
has to be avoided, because overheating could cause local cracking
or other damage. In order to ensure this, a closed loop control of
the laser powder melting operation can be implemented (see FIG. 6):
in this case, a pyrometer 7 is integrated into the laser powder
nozzle 4 which continuously measures the temperature of the local
melt pool. The temperature values are analyzed in real time and fed
back to the laser power control unit, which automatically adjusts
the power level to maintain the optimum temperature for the melting
process. Preferably, a beam shaping optics 8 producing sub-mm laser
spot diameter is used for this process. For a better balance of the
heat input, an additional fast beam oscillation can be implemented
by using a galvanometer scanner, integrated in the beam shaping
optics 8.
[0028] In another embodiment of the invention, the ceramic layer 1
comprises the protruding metallic filler material shaping the
interlocking elements 20: this ceramic layer 1 is used as a
starting preform for an additive manufacturing process, which can
be used to build the interface layer 11 between the ceramic layer 1
and the metallic layer 2. In particular, this operation can be
accomplished by Selective Laser Melting (SLM) inside a work chamber
with controlled atmosphere. For this purpose, the ceramic layer 1
is introduced in the SLM chamber parallel to the powder deposition
plane. The selective laser melting is carried out in such a way
that the new material is formed starting with the interface layer
11. As a particularly interesting option, conformal (near wall)
cooling channels 50, as shown in FIG. 7, can be introduced in close
proximity to the hot interface between the ceramic layer 1 and the
metallic layer 2: the resulting hybrid ceramic/metal compound is
then brazed to the metallic layer 2 as described above.
[0029] Using one of the manufacturing sequences or steps described
above, large quantities of standardized ceramic layer 1/interface
layer 11 elements having the configuration 10 of the present
invention can be produced, which can then be securely bonded to a
large metallic layer 2, such as, for example, a combustor liner in
a gas turbine.
[0030] The main advantages of the method of the invention using
laser metal forming/selective laser melting process allows to build
a mechanical joint between a ceramic layer 1 and a metallic
structure 2 (carrier structure) with very low residual stresses and
minimized stress concentration in the ceramic layer 1. The joint
design allows accommodating the strains due to the thermal mismatch
between the ceramic insulation material configuring the ceramic
layer 1 and the metallic layer 2. Additional strain compliance can
be introduced by choosing a filler material which has adequate
ductility within the targeted operation range.
[0031] Besides, at least in one embodiment of the method of the
invention, the ceramic layer 1 does not need machining prior to
joining and the variability of the ceramic's shape due to
manufacturing tolerances and other effects like uncontrolled
shrinkage during the sintering of the ceramic material before it
being shaped (called green ceramic material) are compensated by the
flexible laser metal forming step in combination with 3D scanning.
The localized heating during the forming of the metallic joint also
reduces the thermal shock intensity in the ceramic layer 1 during
the manufacturing. All these benefits reduce the probability of
pre-cracking the ceramic material during the joining of the ceramic
layer 1 together with the interface layer 11 and the metallic layer
2. Moreover, the process of the invention reduces crack formation
during high temperature operation and transient loads: this reduces
the probability of premature failure of the ceramic material.
[0032] Although the present invention has been fully described in
connection with preferred embodiments, it is evident that
modifications may be introduced within the scope thereof, not
considering this as limited by these embodiments, but by the
contents of the following claims.
* * * * *