U.S. patent application number 15/006900 was filed with the patent office on 2017-05-25 for tooling for vapor deposition.
The applicant listed for this patent is United Technologies Corporation. Invention is credited to Brian T. Hazel, Eric Jorzik, David A. Litton, Michael J. Maloney, James W. Neal, Kevin W. Schlichting.
Application Number | 20170144181 15/006900 |
Document ID | / |
Family ID | 57389352 |
Filed Date | 2017-05-25 |
United States Patent
Application |
20170144181 |
Kind Code |
A1 |
Neal; James W. ; et
al. |
May 25, 2017 |
TOOLING FOR VAPOR DEPOSITION
Abstract
An embodiment of an apparatus includes a first crucible in
communication with a deposition chamber, an energy source, and a
workpiece fixture. The first crucible includes a plurality of walls
defining an upper recess and a first lower recess, at least the
upper recess open to an interior of the deposition chamber. The
energy source is configured to selectively apply and direct energy
within the deposition chamber, including toward the first crucible.
The workpiece fixture includes tooling and a plurality of workpiece
holders configured to retain at least one workpiece selectively
within the deposition chamber. The tooling includes at least one
wall separating at least a first of the plurality of workpiece
holders from a second of the plurality of workpiece holders.
Inventors: |
Neal; James W.; (Ellington,
CT) ; Schlichting; Kevin W.; (South Glastonbury,
CT) ; Hazel; Brian T.; (Avon, CT) ; Litton;
David A.; (West Hartford, CT) ; Jorzik; Eric;
(Montgomery, NY) ; Maloney; Michael J.;
(Marlborough, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
United Technologies Corporation |
Hartford |
CT |
US |
|
|
Family ID: |
57389352 |
Appl. No.: |
15/006900 |
Filed: |
January 26, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62258892 |
Nov 23, 2015 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B05B 15/62 20180201;
C23C 14/243 20130101; C23C 14/24 20130101; C23C 14/505
20130101 |
International
Class: |
B05B 15/06 20060101
B05B015/06 |
Claims
1. An apparatus comprising: a deposition chamber; a first crucible
including a plurality of walls defining an upper recess and a first
lower recess, at least the upper recess open to an interior of the
deposition chamber; an energy source configured to selectively
apply and direct energy within the deposition chamber, including
toward the first crucible; and a workpiece fixture comprising: a
plurality of workpiece holders configured to retain at least one
workpiece selectively within the deposition chamber; and tooling
including at least one wall separating at least a first of the
plurality of workpiece holders from a second of the plurality of
workpiece holders.
2. The apparatus of claim 1, wherein the plurality of workpiece
holders comprises: a first workpiece holder configured to retain a
first workpiece in a first coating zone in the deposition chamber;
and a second workpiece holder configured to retain a second
workpiece in a second coating zone in the deposition chamber;
wherein the at least one wall separates the first workpiece holder
and the second workpiece holder.
3. The apparatus of claim 2, further comprising a second crucible;
wherein the first crucible is in communication with the first
coating zone, and the second crucible is in communication with the
second coating zone.
4. The apparatus of claim 1, wherein the workpiece fixture further
comprises: a first arm configured to manipulate at least one of the
plurality of workpiece holders about a first longitudinal axis.
5. The apparatus of claim 4, wherein the workpiece fixture further
comprises: a triaxial shaft supporting the plurality of workpiece
holders, the triaxial shaft including at least the first arm.
6. The apparatus of claim 5, wherein ones of the plurality of
workpiece holders are secured to a plurality of rakes connected to
the triaxial shaft, and the triaxial shaft is configured to drive
rotation of the rakes, and in turn, rotation of the plurality of
workpiece holders about at least the first longitudinal axis.
7. The apparatus of claim 6, wherein the triaxial shaft is
configured to drive rotation of the rakes about at least the first
longitudinal axis so as to expose different portions of each of the
plurality of workpieces to a plurality of vapor plumes generated
from energy directed to coating feedstock disposed in the
deposition chamber.
8. The apparatus of claim 1, and further comprising: a magazine
positionable within deposition chamber, wherein the magazine
retains a plurality of crucibles including the first crucible.
9. The apparatus of claim 8, wherein the magazine is positioned in
the deposition chamber such that at least the upper recess of the
first crucible is in line with the first workpiece holder.
10. The apparatus of claim 1, wherein the at least one wall
includes a plurality of baffle walls defining at least a portion of
a first coating subchamber and a second coating subchamber.
11. The apparatus of claim 1, wherein the at least one wall
includes a wall with a first thermally reflective surface facing
the first workpiece holder, and a second thermally reflective
surface facing the second workpiece holder.
12. The apparatus of claim 11, wherein the first thermally
reflective surface is spaced apart from the second thermally
reflective surface, defining a thermal buffer space
therebetween.
13. A workpiece fixture for a vapor deposition apparatus comprises:
a plurality of workpiece holders configured to retain at least one
workpiece selectively within a vapor deposition chamber; and
tooling including at least one wall separating at least a first of
the plurality of workpiece holders from a second of the plurality
of workpiece holders.
14. The workpiece fixture of claim 13, wherein the plurality of
workpiece holders comprises: a first workpiece holder configured to
retain a first workpiece in a first coating zone in the deposition
chamber; and a second workpiece holder configured to retain a
second workpiece in a second coating zone in the deposition
chamber; wherein the at least one wall separates the first
workpiece holder and the second workpiece holder.
15. The workpiece fixture of claim 13, and further comprising: a
first arm configured to manipulate at least one of the plurality of
workpiece holders about a first longitudinal axis.
16. The workpiece fixture of claim 15, and further comprising: a
triaxial shaft supporting a plurality of workpiece holders, the
triaxial shaft including at least the first arm.
17. The workpiece fixture of claim 16, wherein ones of the
plurality of workpiece holders are secured to a plurality of rakes
connected to the triaxial shaft, and the triaxial shaft is
configured to drive rotation of the rakes, and in turn, rotation of
the plurality of workpiece holders about at least the first
longitudinal axis.
18. The workpiece fixture of claim 13, wherein the at least one
wall includes a plurality of baffle walls defining at least a
portion of a first coating subchamber and at least a portion of a
second coating subchamber.
19. The workpiece fixture of claim 13, wherein the at least one
wall includes a wall with a first thermally reflective surface
facing the first workpiece holder, and a second thermally
reflective surface facing the second workpiece holder.
20. The workpiece fixture of claim 19, wherein the first thermally
reflective surface is spaced apart from the second thermally
reflective surface, defining a thermal buffer space therebetween.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application claims the benefit of U.S. Provisional
Application No. 62/258,892 filed Nov. 23, 2015 for "TOOLING,
CRUCIBLE, AND FEEDSTOCK FOR VAPOR DEPOSITION" by James W. Neal,
Kevin W. Schlichting, Brian T. Hazel, David A. Litton, Eric Jorzik,
and Michael J. Maloney.
BACKGROUND
[0002] The disclosure relates generally to coating apparatus and
methods, and more specifically to physical vapor deposition.
[0003] Electron Beam Physical Vapor Deposition (EB-PVD) processes
and apparatus utilize a cloud of vaporized material which is
solidified upon at least one workpiece surface in a deposition
chamber. Vaporized material for deposition can be generated by
energizing feedstock material which can be retained in a conductive
crucible.
[0004] Despite efforts at identifying favorable coating parameters,
there are frequently issues around the edges of vapor clouds and
with uniformly exposing surfaces of certain irregularly shaped
workpieces to the vapor plume(s). Coating multiple workpieces in a
chamber increases the risk of irregular or uneven application due
to overlapping vapor plumes from multiple feedstocks distributed
through the chamber.
SUMMARY
[0005] An embodiment of an apparatus includes a first crucible in
communication with a deposition chamber, an energy source, and a
workpiece fixture. The first crucible includes a plurality of walls
defining an upper recess and a first lower recess, at least the
upper recess open to an interior of the deposition chamber. The
energy source is configured to selectively apply and direct energy
within the deposition chamber, including toward the first crucible.
The workpiece fixture includes tooling and a plurality of workpiece
holders configured to retain at least one workpiece selectively
within the deposition chamber. The tooling includes at least one
wall separating at least a first of the plurality of workpiece
holders from a second of the plurality of workpiece holders.
[0006] An embodiment of a workpiece fixture for a vapor deposition
apparatus includes tooling and a plurality of workpiece holders
configured to retain at least one workpiece selectively within a
deposition chamber. The tooling includes at least one wall
separating at least a first of the plurality of workpiece holders
from a second of the plurality of workpiece holders.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a schematic cross-sectional view of an example
coating apparatus.
[0008] FIG. 2 is a detailed view of a deposition chamber portion of
the example coating apparatus and tooling in use.
[0009] FIG. 3 shows a top view of a workpiece fixture for use in a
deposition chamber.
[0010] FIG. 4 shows an arrangement of crucibles in a magazine for
processing through the apparatus.
[0011] FIG. 5A shows an example vapor cloud shape at a first
chamber pressure.
[0012] FIG. 5B shows an example vapor cloud shape at a second
chamber pressure higher than the first chamber pressure.
[0013] FIG. 5C shows an example vapor cloud shape at a third
chamber pressure higher than the second chamber pressure.
[0014] FIG. 6A is a top view of an alternative crucible having a
single lower recess.
[0015] FIG. 6B is a side view of the alternative crucible shown in
FIG. 6A.
[0016] FIG. 6C is a top view of an alternative crucible with
multiple lower recesses.
[0017] FIG. 6D is a side view of the alternative crucible shown in
FIG. 6C.
[0018] FIG. 7A is a top view of an alternative crucible having an
enlarged lower recess.
[0019] FIG. 7B is a side view of the alternative crucible shown in
FIG. 7A.
DETAILED DESCRIPTION
[0020] Electron Beam Physical Vapor Deposition (EB-PVD) processes
and apparatus utilize a cloud of vaporized material which is
solidified on one or more workpieces in a chamber. Particularly but
not exclusively for multiple and/or complex workpieces, tooling
such as shields or boxes around a workpiece allows for
substantially uniform coating of each workpiece by optimizing
heating of each workpiece and preventing overlap of multiple vapor
clouds or plumes, each of which can be dedicated to one or more
workpieces. Crucibles, which retain coating feedstock, can be
configured with various features and can work in conjunction with,
or independently of, the tooling to improve coating of multiple
and/or complex workpieces.
[0021] FIG. 1 shows a non-limiting example embodiment of a coating
apparatus/system (coater) 10, which generally includes carrier and
drive system 12, loading station or chamber 14, optional preheat
chamber 16, and deposition chamber 18. The example carrier and
drive system 12 can include one or more workpiece fixtures 20
holding workpieces 22 at one end of a sting assembly (sting) 24.
While only one fixture 20 is shown, there can be more than one
fixture 20 each carrying workpieces 22 in an associated group of
workpieces.
[0022] There are numerous ways to move workpieces into, out of, and
around deposition chamber 18, only one non-limiting example of
which is shown in FIG. 1. Drive mechanism (e.g., an actuator) 26
can be operable to drive sting assembly 24 in one or more
directions. For example, sting 24 can include inner member 28B
partially concentrically within outer member 28A. Drive mechanism
26 can be mounted to outer member 28A to longitudinally shift outer
member 28A (and thereby inner member 28B). Drive mechanism 26 can
also rotate inner member 28B relative to outer member 28A about
axis A.sub.1.
[0023] In this non-limiting example, drive mechanism 26 can have a
screw drive mechanism (e.g., electric motor driven) or other
suitable construction for longitudinally shifting sting 24 and
fixture 20 in associated loading station or chamber 14.
Additionally or alternatively, drive mechanism 26 can be part of a
robotic system tailored for automated loading and unloading of
workpieces 22 into the various chambers 14, 16, 18. One or more
workpiece holders (shown in FIGS. 2 and 3) can be mounted at an end
of inner member 28B closest to, or within deposition chamber 18,
depending on the position of sting 24.
[0024] Each fixture 20 can include components which are rotatable
about at least one longitudinal axis (e.g., longitudinal horizontal
axis A.sub.1) in response to various manual or automated commands.
A control system 32 can include an appropriately configured
microcomputer, microcontroller, or other controller being
configured by software and/or hardware to perform the functions
described herein, among others not explicitly described. Control
system 32 can be in communication (wired and/or wirelessly) to
various controllable system components as well as to sensors, input
devices for receiving user input, and display devices (not shown
for clarity).
[0025] For preheating workpieces 22, coating system 10 can include
an optional preheat chamber 16, with workpiece preheater 34,
positioned on a side of deposition chamber 18. Preheater 34 can be
any suitable thermal device capable of providing heating such as
conductive or radiative heating. Preheater 34 can additionally or
alternatively include electron beam guns directed to interior 36.
In embodiments omitting preheater 34, chamber 16, between loading
chamber 14 and deposition chamber 18, can additionally or
alternatively serve as a transfer chamber for staging or other
interim processing and preparation steps.
[0026] First gate valve 38 can be positioned at one end of preheat
chamber 16, i.e., between interior 36 of preheat chamber 16 and
interior 42 of loading chamber 14. Second gate valve 44 can be
disposed at an opposing end of preheat chamber 16. Second gate
valve 44 would thus be between interior 36 of preheat chamber 16
and interior 46 of deposition chamber 18. Each of the valves 38, 44
can additionally or alternatively be replaced by two or more valves
so as to allow further isolation of chambers 14, 16, 18 or to allow
various alternative couplings of multiple loading chambers 14,
preheat chambers 16, and/or deposition chambers 18.
[0027] Loading chamber 14 can have one or more loading doors 48 and
a loading drive system/mechanism (not visible in FIG. 1). For
purposes of schematic illustration, door 48 is shown in FIG. 1 as
being positioned to close an opening or port at the top of loading
chamber 14. However, such door(s) 48 can additionally or
alternatively be positioned at one or both sides of chamber 14, or
below. When the appropriate gate valves 38, 44 are open, a loading
drive system/mechanism can shift workpieces 22 into preheat chamber
16, or all the way into deposition chamber 18. The loading
mechanism can be a part of carrier/drive system 12, or can include
independent actuator(s) or controls. For purposes of deposition,
one or more electron guns or other energy source can be positioned
at or within deposition chamber 18 to each direct an associated
energy beam to feedstock material. As shown in FIG. 2, the
feedstock material can include ingots or other masses of
ceramic-forming material each in an associated crucible.
[0028] For introducing a reactive gas (e.g., oxygen for combining
with the initially vaporized material in the vapor clouds to make
up for oxygen lost from the evaporated ceramic) a gas source 52 can
be provided. One example of a reactive gas can be essentially pure
oxygen. The gas source 52 can be connected to an outlet (e.g., a
manifold in deposition chamber 18, omitted for clarity) via a gas
line 56 and controlled by a gas valve 58. Line 56 can be connected
to one or more extensions through sting 24 to an outlet/manifold in
deposition chamber 18, or can be routed differently to provide
reactive gas if and when it is needed for deposition.
[0029] Coating chamber 18 can include at least one vacuum port 66
(having one or more pumps with associated conduits and valves,
omitted for clarity) through one of a plurality of chamber walls
60. In certain embodiments, such as the example shown in FIG. 1,
first, second, and third vacuum ports 62, 64, 66 can be associated
with respective chambers 14, 16, 18.
[0030] FIG. 2 shows a detailed view of deposition chamber 18 with
the apparatus in use, as indicated by the dashed line labeled `FIG.
2` in FIG. 1. Fixture 20 can include at least a first workpiece
holder 67A configured to retain at least first workpiece 22A in
deposition chamber 18. Here, second workpiece holder 67B is
configured to retain second workpiece 22B and third workpiece
holder 67C is configured to retain second workpiece 22C. Fixture 20
can include one or more motorized or actuated arms to rotate
workpiece(s) 22A, 22B, 22C about at least longitudinal axis
A.sub.1. FIG. 3 shows a different view of fixture 20 in the form of
a triaxial shaft.
[0031] FIG. 2 also shows crucibles 72A, 72B, 72C, at or near the
base of deposition chamber 18, which are configured to retain
feedstock material (e.g., from feedstock ingots)70A, 70B, 70C
therein. Energy sources 68A, 68B, 68C (e.g., electron beam guns)
direct vaporization energy 69A, 69B, 69C toward crucibles 72A, 72B,
72C for energizing any coating feedstock retained therein and
generating corresponding vapor clouds or plumes 71A, 71B, 71C.
Feedstock material 70A, 70B, 70C can either be of similar form to a
desired coating material, or it can be a precursor combinable with
a carrier of mixing gas (e.g., oxygen) to form a desired chemistry
under system operating conditions.
[0032] In certain embodiments, one or more crucibles 72 (e.g.,
crucibles 72A, 72B, 72C) can be translated within deposition
chamber 18 via magazine 100 (shown in more detail in FIG. 4).
Magazine 100 can be configured, for example, to align feedstock
material 70A, 70B, 70C and resulting plumes 71A, 71B, 71C with
corresponding coating zones 76A, 76B, 76C with minimal overlap.
Magazine 100 can also retain crucibles 72 in any other suitable
configuration relative to one or more coating zones and/or
workpieces.
[0033] Also shown in FIG. 4, crucibles 72 can each include an inert
body 106 including one or more walls 110 defining recesses 108 for
retaining feedstock. The recesses are open to deposition chamber 18
to allow vapor plumes resulting from energizing feedstock to flow
toward the workpiece(s). Subsequent figures also show how the shape
of the recesses can result in differently contoured vapor plumes
for differently shaped workpieces.
[0034] Returning to FIG. 2, one or more coating zones can be formed
within deposition chamber 18. In the example shown, tooling 78,
such as baffles 80, can be provided to retain and separate
workpieces 22A, 22B, 22C in individual first, second, and third
coating zones 76A, 76B, 76C within deposition chamber interior 46.
Tooling 78 can help confine vapor plumes into well-defined,
physically separated coating zones so that each respective plume
71A, 71B, 71C can be in selective or constant communication with
respective coating zones 76A, 76B, 76C.
[0035] Tooling 78 can be configured to allow for more predictable
and uniform coating of multiple workpieces in a single coating run,
particularly when less vacuum is applied causing higher pressures
in the deposition chamber during coating. As is known in the art, a
number of physical deposition processes, such as EB-PVD, are
performed under significant vacuum, typically at pressures at or
less than 2 Pa. Typically, lower pressures (i.e., increased vacuum)
within deposition chamber 18 can provide higher energy states for
the vaporized feedstock, facilitating deposition onto and adherence
with a workpiece.
[0036] However, lower pressures in physical deposition processes
result in larger and more dispersed vapor clouds or plumes,
increasing the likelihood of overlapping clouds when attempting to
coat multiple workpieces or attempting to coat elongated workpieces
with multiple coating regions such as vane doublets and triplets.
Further, larger vapor clouds or plumes may in some instances be
prone to causing irregular coating around the perimeter of the
vapor cloud, resulting in irregular deposition thickness if the
workpiece is located near these perimeters. In such a case, tooling
78 can help ensure the workpieces are located away from the plume
perimeters. In other instances of lower vapor pressure, however,
overlapping vapor plumes produce fewer issues because the average
number of collisions between vapor molecules is low enough that a
single vapor cloud actually improves uniformity. At the same time,
tooling 78 can improve radiative heating of the workpiece even in
lower pressure (higher vacuum) coating conditions by reflecting
energy back to the workpiece.
[0037] The same energy sources 68A, 68B, 68C that vaporize the
feedstock material can be used to heat deposition chamber 18 (e.g.,
by directing their beams to a bed of refractory ceramic gravel,
omitted for clarity). This can provide a preheating of the
deposition chamber 18 (e.g., both before any coating runs and
between coating runs).
[0038] FIG. 3 shows a more detailed view of fixture 20. Here,
fixture 20 is a triaxial shaft fixture having a plurality of
workpiece holders, e.g., workpiece holders 67A, 67B, 67C. Here,
first arm 90A, second arm 90B, and third arm 90C are rotatable
about axis A.sub.1. This multishaft arrangement can ensure uniform
exposure of different workpiece surfaces to the respective vapor
plumes 71A, 71B, 71C (shown in FIG. 2). Second arm 90B and third
arm 90C can rotate about A.sub.1 together (i.e. one rotates into
the page while the other rotates out of the page) or independently
(i.e. they both rotate into the page or both rotate out of the
page).
[0039] Arms 90A, 90B, 90C, one or more of which can be motorized,
can be configured (e.g., with rakes 96) to manipulate at least one
of workpiece holders 67A, 67B, 67C so as to expose different
portions of workpieces 22A, 22B, 22C to vapor plumes (shown in FIG.
2) by energizing feedstock disposed in crucibles 72A, 72B, 72C. One
or more baffles 80A, 80B, 80C, 80D can be secured to one or more
arms 90A, 90B, 90C, and configured to partially or completely
enclose workpieces within subchambers 82A, 82B, 82C in the desired
coating zone(s) 76A, 76B, 76C.
[0040] For purposes of this disclosure, note that description of
separate workpieces can emcompass not only workpieces which are
completely physically separate from one another (e.g., individual
turbine blades or vanes), but also distinct sections of a single
integrated workpiece. For example, an airfoil section and root
section of a turbine blade or vane can be considered separate
workpieces, as can first and second airfoils of a vane doublet.
[0041] One or more of baffles 80A, 80B, 80C, 80D can include one or
more thermally reflective surfaces 92, which can allow for uniform
heating of workpieces 22A, 22B, 22C. Thermal reflectivity and
insulation can be further enhanced by making baffles 80A, 80B, 80C,
80D at least partially hollow, providing one or more thermal buffer
spaces 94 between surfaces 92 to provide more consistent
temperatures in each coating zone 76A, 76B, 76C.
[0042] FIG. 4 shows magazine 100 which is movable into and out of
deposition chamber 18. Magazine 100 includes tray/rack 102 capable
of retaining a plurality of crucibles 72 in a plurality of crucible
receivers 104 at a plurality of coating positions. The material of
crucible body 106 can be inert to the vaporization energy in that
body 106 can provide thermal and electrical conduction to
facilitate vapor formation from the feedstock material (not shown
in FIG. 4) while remaining structurally intact and substantially
phase stable during the coating process to prevent coating
contamination. Crucibles 72 can also be configured with various
means to prevent melting by the applied vaporization energy from
one or more sources (e.g., sources 68A, 68B, 68C shown in FIG. 2.
Such means include but are not limited to providing coolant
passages through the crucible for circulating water or other
cooling fluids therethrough.
[0043] Suitable non-limiting example materials for body 106 can
include copper or an alloy thereof, as well as certain
high-temperature ceramic materials. Recesses 108, defined by one or
more walls 110 of each crucible 72 can be placed in line with the
corresponding workpieces (e.g., workpieces 22A, 22B, 22C in
workpiece holders 67A, 67B, 67C shown in FIGS. 2 and 3) so that a
desired vapor plume can reach a respective workpiece.
[0044] Magazine 100 can also allow (e.g., via communication with
control system 32, shown in FIG. 1) manual or automated positioning
of crucibles 72 so that the resulting plumes (not shown) are in
selective or constant communication with an appropriate coating
zone(s) during a coating run. In certain embodiments, each crucible
72 can be provided with the same or different feedstock
compositions, and can be arranged in such a way so as to allow
multiple coating layers of different chemistries. By way of
non-limiting example, one row of crucibles 72 in magazine 100 can
be provided with ingots (shown in FIG. 2) of a first chemical
composition and an adjacent row can be provided with ingots of a
second, different composition. After one coating run involving one
of the rows of crucibles 72, resulting in a first coating layer,
magazine 100 can be repositioned so that another row of crucibles
72, containing feedstock ingots having the second composition, are
exposed to the one or more workpieces for resulting in a second
coating layer.
[0045] The circular crucibles and corresponding circular recesses
108 shown in FIG. 4 can result in a frustoconical vapor cloud, the
dispersion of which can depend at least in part on the pressure in
the deposition chamber during use. For example, deposition chamber
pressure can be controlled by increasing or decreasing vacuum force
through vacuum port 66 (shown in FIGS. 1 and 2). A comparison of
FIGS. 5A-5C show this relationship between chamber pressure and
dispersion of the vapor plume, when the crucible is maintained as a
single geometry.
[0046] FIG. 5A is an illustration of a vapor plume 120 formed at a
first deposition chamber pressure P.sub.1, approaching 0 Pa (i.e.,
high vacuum). Plume 120 shows wide dispersal of the plume, and most
of the coating vapor particles have high energy to facilitate
coating, as shown in center 124. Around perimeter 122, however,
energy of coating vapor particles is lower than in center 124 and
can result in inconsistent surface deposition when in contact with
particles in perimeter 122. High level of dispersion of vapor plume
120 can tend to overlap with adjacent plumes with multiple
crucibles and feedstocks in a deposition chamber. When a workpiece
or portion of a workpiece is in this overlapping zone, it can cause
excess deposition on that portion of the workpiece resulting in
nonuniform and unpredictable coating thickness.
[0047] FIG. 5B is an illustration of a vapor plume 130 formed at a
second deposition chamber pressure P.sub.2, which is higher than
the first pressure P.sub.1 (FIG. 5A). This can be induced,
according to the apparatus in FIGS. 1 and 2, by reducing the vacuum
at vacuum port 66. Here, the dispersal of plume 130 is reduced as
compared to plume 120 in FIG. 5A, and center 134 of plume 130 is
smaller than center 124 of plume 120. FIG. 5C is an illustration of
a vapor plume 140 formed at a third deposition chamber pressure
P.sub.3, which is higher than second pressure P.sub.2 (FIG. 5B),
and thus resulting in a lower vacuum than in FIG. 5B. Here, the
dispersal of plume 140 is reduced as compared to plume 120 in FIG.
5A and plume 130 in FIG. 5B. The geometries of the plumes 120, 130,
140 illustrate that deposition chamber pressure can be tailored to
achieve desired dispersal of a particular vapor plume.
[0048] Even when deposition chamber pressure is increased to reduce
overlap of adjacent vapor plumes, the higher concentration of vapor
molecules increases the number and energy of collisions. Inventors
have found that higher deposition chamber pressures appear to
increase the likelihood that some fraction of these collisions
result in larger molecules or clusters during transit to the
workpiece. When such particles are allowed to deposit on the
workpiece, coating microstructure can be disrupted, reducing
coating quality. However, baffles 80 can further reduce interaction
of coating plumes to reduce clustering, as well as provide
radiative heat flux to the workpieces in order to maintain a
desired temperature, both of which contribute to coating quality
and consistency. Thus when combined with various crucible/feedstock
shapes and/or the provision of tooling, substantially uniform
deposition can be achieved, even in coating processes using
multiple workpieces or more complex single workpieces with multiple
coating areas (such as but not limited to airfoils and platforms of
vane doublets and triplets).
[0049] Note that FIG. 4 shows a circular crucible shape which can
result in a frustoconical vapor cloud (e.g., as shown in FIGS.
5A-5C). Alternate crucible shapes can accommodate both conventional
circular feedstock, as well as differently shaped (e.g.,
non-circular) feedstock to provide vapor clouds more closely
matching the shape of the workpiece(s) area to be coated so as to
provide more uniform coating thickness, particularly under low
vacuum conditions where energy of the generated vapor is reduced.
Example configurations of these elements are described in more
detail with respect to FIGS. 6A-6D and 7A-7B.
[0050] At least one of the crucibles in a magazine or in a
deposition chamber can include a non-circular shape and/or a
non-circular recess for retaining coating feedstock. As seen in
these figures, the crucibles can be configured to retain a circular
or a non-circular coating feedstock in the similarly circular or
non-circular recesses. These non-circular crucibles, some of which
also have non-circular recesses for retaining corresponding
alternative feedstock ingots, are particularly but not exclusively
suited for a low-vacuum coating process of multiple workpieces
and/or complex workpieces with multiple distinct regions to be
coated. They can also be used in conjunction with tooling secured
to the workpiece fixtures and tailored to the shapes of the
feedstock and workpieces involved.
[0051] FIG. 6A shows non-circular crucible 200 with a generally
oval shape. Body 202 has elongated sidewalls 204 and curved end
walls 206 defining upper recess 210 and lower recess 212 for
retaining coating feedstock ingot 220 therein. When viewed from
above into the recesses, upper recess 210 and lower recess 212 are
of a generally non-circular oval shape. FIG. 6B is a sectional view
of crucible 200, recesses 210, 212, circular feedstock ingot 220,
and vapor plume 222 with center 224 and perimeter 226.
[0052] Oval feedstock ingot 220 is disposed in lower recess 212. A
portion of feedstock ingot 220 is cut away in FIG. 6A to better
show lower recess 212. The elongated oval shape of upper recess 210
can further change the geometry of a formed vapor plume (e.g.,
plume 222) to more closely conform to differently shaped workpieces
(not shown). This can be used in conjunction with deposition
processes utilizing higher chamber pressures to reduce dispersion
of vapor plume 222 (omitted from FIG. 6A for clarity) away from
crucible 200, confining it to a desired coating zone. In use, the
chamber pressure and energy can be selected so that plume center
224 focuses primarily on a particular workpiece or portion thereof.
Perimeter 226 can be further confined via tooling around one or
more workpieces, such as in the examples shown in FIGS. 2 and
3.
[0053] FIG. 6C shows non-circular crucible 250 with a generally
oval shape similar to crucible 200. Body 252 has elongated
sidewalls 254 and curved end walls 256 defining upper recess 260 in
an oval shape (when viewed from above into recess 260). Here, there
are two circular lower recesses 262A, 262B for retaining two
coating feedstock ingots therein. Portions of feedstock ingots
270A, 270B are cut away in FIG. 6C to better show lower recesses
262A, 262B. FIG. 6D is a sectional view of non-circular crucible
250, recesses 260, 262A, 262B, feedstock ingots 270A, 270B, and
vapor plumes 272A, 272B with respective centers 274A, 274B, and
respective perimeters 276A, 276B.
[0054] In certain embodiments, one of feedstock ingots 270A, 270B
can be supplemental or complementary to the other. In certain of
these embodiments, feedstock ingot 270A can have a different
material composition as compared to circular feedstock ingot 270B,
which result in different vapor compositions. This is represented
by different sizes of plumes 272A, 272B.
[0055] In use, the chamber pressure and energy can be selected so
that plume centers 274A, 274B focus primarily on particular
portion(s) of a workpiece. Plume perimeters 276A, 276B can be
further confined via tooling around one or more workpieces, such as
in the examples shown in FIGS. 2 and 3. Alternatively, chamber
pressure and energy can be varied so that plumes 272A, 272B can
overlap during some or all of a particular coating run. This
variation can be used, for example, in situations where two
different solid feedstocks are desired for codeposition.
[0056] FIG. 7A shows non-circular crucible 300 with generally
rectangular body 302 having two generally straight elongated
sidewalls 304, and two shorter straight end walls 306 defining
upper recess 310 and tapered lower recess 312 for retaining coating
feedstock therein. A portion of feedstock ingot 320 is cut away in
FIG. 7A to better show lower recess 312. FIG. 7B is a sectional
view of non-circular crucible 300, recesses 310, 312, tapered
racetrack feedstock ingot 320, and vapor plume 322 (omitted from
FIG. 7A for clarity).
[0057] Upper recess 310 can include one or more rounded internal
corners 314 to modify a generally rectangular shape of upper recess
310 (when viewed from above). This results in what is sometimes
known colloquially as a "racetrack" shape. This in turn can
potentially improve uniformity of vapor plume 322 around its edges
by reducing discontinuities possibly resulting from sharp internal
corners. In this example, body 302 also can include one or more
optionally rounded external corners 308 to maintain substantially
constant wall thickness for uniform heating, as well as to
potentially simplify manufacture of a crucible (e.g., crucible
300).
[0058] The non-circular lower recess 312 (rectangular with rounded
corners) can include one or more cross-sectional dimensions X, and
in turn, a cross-sectional area, varying with a depth D of lower
recess 312 below base 316 of upper recess 310. FIG. 7B shows
cross-sectional dimension X.sub.1, where depth D approaches 0, and
cross-sectional dimension X.sub.2 where depth D approaches
D.sub.max below base 316 of upper recess 310. As depth D increases
below upper crucible surface 316 (i.e., as depth D increases from 0
to D.sub.max), the result is that dimension X can decrease such
that dimension X.sub.2 is smaller than dimension X.sub.1.
[0059] Varying the cross-sectional dimension(s) of lower recess 312
can accommodate tapered feedstock ingot 320, where the desired
vapor concentration can be reduced as coating progresses through
consumption of the feedstock. This can be done to reduce or
eliminate the need to reduce the applied vaporization energy as a
means to control the vapor concentration in plume 322. Since higher
operating pressures (less applied vacuum) in the deposition chamber
can reduce the available energy of the vapor plume, the applied
vaporization energy can be kept more or less constant throughout
the process, improving accuracy of the coating process. In use, the
chamber pressure and energy can be selected so that plume center
324 focuses primarily on a particular workpiece or portion thereof.
Perimeter 326 can be further confined via tooling around one or
more workpieces, such as in the examples shown in FIGS. 2 and
3.
[0060] In additional embodiments, adding curves or edges to
elongated sidewalls 304 and/or end walls 306 can result in an
elongated irregular shape of body 302 to further accommodate
irregularly shaped recesses while ensuring substantially constant
wall thickness.
Discussion of Possible Embodiments
[0061] An embodiment of an apparatus includes a first crucible in
communication with a deposition chamber, an energy source, and a
workpiece fixture. The first crucible includes a plurality of walls
defining an upper recess and a first lower recess, at least the
upper recess open to an interior of the deposition chamber. The
energy source is configured to selectively apply and direct energy
within the deposition chamber, including toward the first crucible.
The workpiece fixture includes tooling and a plurality of workpiece
holders configured to retain at least one workpiece selectively
within the deposition chamber. The tooling includes at least one
wall separating at least a first of the plurality of workpiece
holders from a second of the plurality of workpiece holders.
[0062] The following are non-exclusive descriptions of possible
embodiments of the present invention.
[0063] An apparatus according to an exemplary embodiment of this
disclosure, among other possible things includes a deposition
chamber; a first crucible including a plurality of walls defining
an upper recess and a first lower recess, at least the upper recess
open to an interior of the deposition chamber; an energy source
configured to selectively apply and direct energy within the
deposition chamber, including toward the first crucible; and a
workpiece fixture comprising: a plurality of workpiece holders
configured to retain at least one workpiece selectively within the
deposition chamber; and tooling including at least one wall
separating at least a first of the plurality of workpiece holders
from a second of the plurality of workpiece holders.
[0064] The apparatus of the preceding paragraph can optionally
include, additionally and/or alternatively, any one or more of the
following features, configurations and/or additional
components:
[0065] A further embodiment of the foregoing apparatus, wherein the
plurality of workpiece holders includes: a first workpiece holder
configured to retain a first workpiece in a first coating zone in
the deposition chamber; and a second workpiece holder configured to
retain a second workpiece in a second coating zone in the
deposition chamber; wherein the at least one wall separates the
first workpiece holder and the second workpiece holder.
[0066] A further embodiment of any of the foregoing apparatus,
further comprising a second crucible; wherein the first crucible is
in communication with the first coating zone, and the second
crucible is in communication with the second coating zone.
[0067] A further embodiment of any of the foregoing apparatus,
wherein the workpiece fixture further comprises: a first arm
configured to manipulate at least one of the plurality of workpiece
holders about a first longitudinal axis.
[0068] A further embodiment of any of the foregoing apparatus,
wherein the workpiece fixture further comprises: a triaxial shaft
supporting the plurality of workpiece holders, the triaxial shaft
including at least the first arm.
[0069] A further embodiment of any of the foregoing apparatus,
wherein ones of the plurality of workpiece holders are secured to a
plurality of rakes connected to the triaxial shaft, and the
triaxial shaft is configured to drive rotation of the rakes, and in
turn, rotation of the plurality of workpiece holders about at least
the first longitudinal axis.
[0070] A further embodiment of any of the foregoing apparatus,
wherein the triaxial shaft is configured to drive rotation of the
rakes about at least the first longitudinal axis so as to expose
different portions of each of the plurality of workpieces to a
plurality of vapor plumes generated from energy directed to coating
feedstock disposed in the deposition chamber.
[0071] A further embodiment of any of the foregoing apparatus, and
further comprising: a magazine positionable within deposition
chamber, wherein the magazine retains a plurality of crucibles
including the first crucible.
[0072] A further embodiment of any of the foregoing apparatus,
wherein the magazine is positioned in the deposition chamber such
that at least the upper recess of the first crucible is in line
with the first workpiece holder.
[0073] A further embodiment of any of the foregoing apparatus,
wherein the at least one wall includes a plurality of baffle walls
defining at least a portion of a first coating subchamber and a
second coating subchamber.
[0074] A further embodiment of any of the foregoing apparatus,
wherein the at least one wall includes a wall with a first
thermally reflective surface facing the first workpiece holder, and
a second thermally reflective surface facing the second workpiece
holder.
[0075] A further embodiment of any of the foregoing apparatus,
wherein the first thermally reflective surface is spaced apart from
the second thermally reflective surface, defining a thermal buffer
space therebetween.
[0076] An embodiment of a workpiece fixture for a vapor deposition
apparatus includes tooling and a plurality of workpiece holders
configured to retain at least one workpiece selectively within a
deposition chamber. The tooling includes at least one wall
separating at least a first of the plurality of workpiece holders
from a second of the plurality of workpiece holders.
[0077] A workpiece fixture according to an exemplary embodiment of
this disclosure, among other possible things includes a plurality
of workpiece holders configured to retain at least one workpiece
selectively within a vapor deposition chamber; and tooling
including at least one wall separating at least a first of the
plurality of workpiece holders from a second of the plurality of
workpiece holders.
[0078] The apparatus of the preceding paragraph can optionally
include, additionally and/or alternatively, any one or more of the
following features, configurations and/or additional
components:
[0079] A further embodiment of the foregoing workpiece fixture,
wherein the plurality of workpiece holders comprises: a first
workpiece holder configured to retain a first workpiece in a first
coating zone in the deposition chamber; and a second workpiece
holder configured to retain a second workpiece in a second coating
zone in the deposition chamber; wherein the at least one wall
separates the first workpiece holder and the second workpiece
holder.
[0080] A further embodiment of any of the foregoing workpiece
fixtures, and further comprising: a first arm configured to
manipulate at least one of the plurality of workpiece holders about
a first longitudinal axis.
[0081] A further embodiment of any of the foregoing workpiece
fixtures, and further comprising: a triaxial shaft supporting a
plurality of workpiece holders, the triaxial shaft including at
least the first arm.
[0082] A further embodiment of any of the foregoing workpiece
fixtures, wherein ones of the plurality of workpiece holders are
secured to a plurality of rakes connected to the triaxial shaft,
and the triaxial shaft is configured to drive rotation of the
rakes, and in turn, rotation of the plurality of workpiece holders
about at least the first longitudinal axis.
[0083] A further embodiment of any of the foregoing workpiece
fixtures, wherein the at least one wall includes a plurality of
baffle walls defining at least a portion of a first coating
subchamber and at least a portion of a second coating
subchamber.
[0084] A further embodiment of any of the foregoing workpiece
fixtures, wherein the at least one wall includes a wall with a
first thermally reflective surface facing the first workpiece
holder, and a second thermally reflective surface facing the second
workpiece holder.
[0085] A further embodiment of any of the foregoing workpiece
fixtures, wherein the first thermally reflective surface is spaced
apart from the second thermally reflective surface, defining a
thermal buffer space therebetween.
[0086] While the invention has been described with reference to an
exemplary embodiment(s), it will be understood by those skilled in
the art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment(s) disclosed, but that the invention will
include all embodiments falling within the scope of the appended
claims.
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