U.S. patent application number 15/827339 was filed with the patent office on 2019-05-30 for non-equilibrium alloy cold spray feedstock powders, manufacturing processes utilizing the same, and articles produced thereby.
This patent application is currently assigned to HONEYWELL INTERNATIONAL INC.. The applicant listed for this patent is HONEYWELL INTERNATIONAL INC.. Invention is credited to Paul Chipko, Robert Franconi, Daniel Greving, Patrick Hinke, Bahram Jadidian, Harry Lester Kington, James Piascik.
Application Number | 20190161865 15/827339 |
Document ID | / |
Family ID | 64564586 |
Filed Date | 2019-05-30 |
United States Patent
Application |
20190161865 |
Kind Code |
A1 |
Chipko; Paul ; et
al. |
May 30, 2019 |
NON-EQUILIBRIUM ALLOY COLD SPRAY FEEDSTOCK POWDERS, MANUFACTURING
PROCESSES UTILIZING THE SAME, AND ARTICLES PRODUCED THEREBY
Abstract
Methods for producing Non-Equilibrium Alloy (NEA) feedstock
powders are disclosed, as are methods for fabricating articles from
such NEA feedstock powders utilizing Additive Manufacturing (AM)
cold spray processes. In various embodiments, the method includes
the step or process obtaining an NEA feedstock powder, which is
composed of an alloy matrix throughout which a first minority
constituent is dispersed. The first minority constituent
precipitates from the alloy matrix when the NEA feedstock powder is
exposed to temperatures exceeding a critical temperature threshold
(T.sub.CRITICAL) for a predetermined time period. An AM cold spray
process is carried-out to produce a near-net article from the NEA
feedstock powder, which is exposed to a maximum temperature
(T.sub.SPRAY.sub._.sub.MAX) during the cold spray process. The
near-net article is then further processed to yield a finished
article. To substantially preserve the non-equilibrium state of the
feedstock powder, T.sub.SPRAY.sub._.sub.MAX is maintained below
T.sub.CRITICAL through the cold spray process.
Inventors: |
Chipko; Paul; (Blairstown,
NJ) ; Piascik; James; (Randolph, NJ) ;
Kington; Harry Lester; (Scottsdale, AZ) ; Greving;
Daniel; (Scottsdale, AZ) ; Hinke; Patrick;
(Phoenix, AZ) ; Franconi; Robert; (New Hartford,
CT) ; Jadidian; Bahram; (Watchung, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HONEYWELL INTERNATIONAL INC. |
Morris Plains |
NJ |
US |
|
|
Assignee: |
HONEYWELL INTERNATIONAL
INC.
Morris Plains
NJ
|
Family ID: |
64564586 |
Appl. No.: |
15/827339 |
Filed: |
November 30, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22F 2302/45 20130101;
B22F 1/0011 20130101; B22F 2301/20 20130101; B22F 1/0085 20130101;
B33Y 40/00 20141201; B22F 2301/052 20130101; B22F 1/0055 20130101;
B22F 2003/248 20130101; B22F 3/008 20130101; B22F 3/24 20130101;
C22C 19/007 20130101; B22D 23/003 20130101; C22C 1/0433 20130101;
C22C 19/03 20130101; B22F 2301/35 20130101; B22F 3/1017 20130101;
B33Y 10/00 20141201; C23C 24/04 20130101; B22F 5/04 20130101; C22C
1/0416 20130101; C22C 21/00 20130101; B22F 5/009 20130101 |
International
Class: |
C23C 24/04 20060101
C23C024/04; C22C 21/00 20060101 C22C021/00; B22F 3/10 20060101
B22F003/10; B22F 3/24 20060101 B22F003/24; B22F 1/00 20060101
B22F001/00; B22F 5/00 20060101 B22F005/00; B22D 23/00 20060101
B22D023/00 |
Claims
1. A method, comprising: obtaining a Non-Equilibrium Alloy (NEA)
feedstock powder composed of an alloy matrix and throughout which a
first minority constituent is dispersed, the first minority
constituent precipitating from the alloy matrix when the NEA
feedstock powder is exposed to temperatures exceeding a critical
temperature threshold (T.sub.CRITICAL) for a predetermined time
period; utilizing an Additive Manufacturing (AM) cold spray process
to fabricate a near-net article from the NEA feedstock powder; and
further processing the near-net article to yield a finished
article; wherein the near-net article is exposed to a maximum
temperature (T.sub.SPRAY.sub._.sub.MAX) during the cold spray
process; and wherein T.sub.SPRAY.sub._.sub.MAX is maintained below
T.sub.CRITICAL to preserve, at least in substantial part, a
non-equilibrium state of the NEA feedstock powder through the cold
spray process.
2. The method of claim 1 wherein T.sub.CRITICAL is less than a melt
point of the NEA feedstock powder and greater than 300 degrees
Celsius.
3. The method of claim 1 wherein further processing comprises:
subjecting the near-net article to a post-spray annealing process
following the AM cold spray process; and machining selected
surfaces of the near-net article after the post-spray annealing
process; wherein, during the post-spray annealing and machining
process steps, the near-net article is exposed to maximum
temperatures less than T.sub.CRITICAL.
4. The method of claim 3 wherein the near-net article is exposed to
a maximum annealing temperature (T.sub.ANNEAL) during the
post-spray annealing process; and wherein T.sub.ANNEAL is greater
than 1/2 T.sub.CRITICAL and less than T.sub.CRITICAL.
5. The method of claim 1 further comprising selecting the NEA
feedstock powder such that: the NEA feedstock powder is composed
predominately of aluminum by weigh percent; and the first minority
constituent is selected from the group consisting of iron and
silicon.
6. The method of claim 1 further comprising selecting the NEA
feedstock powder to contain, by weight percent: between 85 and 90
aluminum; between 8 and 10 percent iron; between 1 and 3 percent
silicon; and between 1 and 2 percent vanadium.
7. The method of claim 1 further comprising selecting the NEA
feedstock to have a particle size ranging from approximately 10 to
approximately 140 microns in maximum dimension.
8. The method of claim 1 further comprising selecting the NEA
feedstock powder to consist substantially entirely of flake-shaped
particles ranging from approximately 10 microns to approximately 90
microns in maximum dimension.
9. The method of claim 1 wherein the NEA feedstock powder is
produced utilizing a process comprising: forming a molten alloy
into a solid shape utilizing a casting process having a cooling
rate equal to or greater than approximately 1.times.10.sup.6
degrees Celsius per second; and mechanically converting the solid
shape into the NEA feedstock powder.
10. The method of claim 9 wherein forming comprising forming the
molten alloy into a ribbon utilizing a planar flow casting process
having a cooling rate equal to or greater than approximately
1.times.10.sup.7 degrees Celsius per second.
11. The method of claim 9 wherein mechanically converting
comprises: chopping the solid shape into flake-shaped pieces having
an average size range; and attrition milling the flake-shaped
pieces to reduce an average size range thereof.
12. The method of claim 1 wherein the NEA feedstock particles are
subjected to a pre-spray anneal process having a maximum anneal
temperature (T.sub.ANNEAL.sub._.sub.MAX) prior to the AM cold spray
process; and wherein T.sub.ANNEAL.sub._.sub.MAX is less than
T.sub.CRITICAL.
13. The method of claim 1 wherein the finished article comprises a
gas turbine engine component; wherein, during the AM cold spray
process, the NEA feedstock powder is deposited around a sacrificial
structure; and wherein further processing comprises removing the
sacrificial structure to create a flow passage through the gas
turbine engine component.
14. A method, comprising: forming a molten alloy into a solid
Non-Equilibrium Alloy (NEA) body utilizing a casting process having
a cooling rate equal to or greater than approximately
1.times.10.sup.6 degrees Celsius per second; mechanically
converting the solid NEA body into a NEA feedstock powder; and
subjecting the feedstock powder to an anneal processing having a
maximum anneal temperature (T.sub.ANNEAL.sub._.sub.MAX); wherein
the NEA feedstock powder comprises an alloy matrix throughout which
a first minority constituent is dispersed; wherein the first
minority constituent precipitates from the alloy matrix when the
NEA feedstock powder is exposed to temperatures exceeding a
critical temperature threshold T.sub.CRITICAL for a predetermined
time period; and wherein T.sub.CRITICAL is less than a melt point
of the NEA feedstock powder and greater than
T.sub.ANNEAL.sub._.sub.MAX.
15. The method of claim 14 wherein forming comprises forming the
molten alloy into an NEA ribbon utilizing a planar flow casting
process having a cooling rate equal to or greater than
approximately 1.times.10.sup.7 degrees Celsius per second.
16. The method of claim 14 wherein mechanically converting
comprises mechanically converting the solid NEA body into a NEA
feedstock powder consisting substantially entirely of flake-shaped
particles ranging from approximately 10 microns to approximately 90
microns in maximum dimension.
17. The method of claim 14 further comprising formulating the NEA
feedstock powder such that: the NEA feedstock powder is
predominately composed of a first material by weight percent, the
first material selected from the group consisting of aluminum and
nickel; and the first minority constituent forms dispersoids within
the NEA feedstock powder, the dispersoids selected from the group
consisting of silicide dispersoids and carbide dispersoids.
18. The method of claim 14 further comprising formulating the NEA
feedstock powder such that T.sub.CRITICAL is between about 400
degrees Celsius and about 450 degrees Celsius.
19. A method, comprising: utilizing an Additive Manufacturing (AM)
cold spray process to fabricate a near-net article from a
Non-Equilibrium Alloy (NEA) feedstock powder having a melt point
(T.sub.ALLOY.sub._.sub.MP), the NEA feedstock powder comprising: an
aluminum alloy matrix; and a non-trace amount of silicon contained
in the aluminum alloy matrix and precipitating therefrom when the
NEA feedstock powder is exposed to temperatures exceeding a
critical temperature threshold (T.sub.CRITICAL) for a predetermined
time period; after utilizing the AM cold spray process to fabricate
the near-net article from a NEA feedstock powder, annealing the
near-net article at a maximum annealing temperature (T.sub.ANNEAL);
wherein the steps of utilizing and annealing are performed such
that
T.sub.ANNEAL<T.sub.CRITICAL<T.sub.ALLOY.sub._.sub.MP.
20. The method of claim 19 wherein T.sub.ANNEAL.sub._.sub.MAX is
greater than T.sub.CRITICAL minus 150 degrees Celsius and less than
T.sub.CRITICAL minus 25 degrees Celsius.
Description
TECHNICAL FIELD
[0001] The present disclosure relates generally to dynamic cold gas
spray processes and, more particularly, to non-equilibrium alloy
feedstock powders, cold spray-based processes for additively
manufacturing articles with such feedstock powders, and articles
produced utilizing such processes.
ABBREVIATIONS
[0002] Abbreviations appearing less frequently in this document are
defined upon initial usage, while abbreviations appearing with
greater frequency are defined below.
[0003] Al--Aluminum;
[0004] AM--Additive Manufacturing:
[0005] DED--Direct Energy Deposition;
[0006] DMLS--Direct Metal Laser Sintering;
[0007] GTE--Gas Turbine Engine;
[0008] HIP--Host Isostatic Pressing;
[0009] NEA--Non-Equilibrium Alloy;
[0010] SEM--Scanning Electronic Microscope;
[0011] Wt %--Weight percent;
[0012] .degree. C.--degrees Celsius; and
[0013] .degree. C./s--degrees Celsius per second.
BACKGROUND
[0014] Aerospace components, such as GTE components and airborne
valves, are commonly fabricated from alloy powders utilizing powder
metallurgy processes. HIP processes, in particular, are often
utilized to transform powder bodies into near-net shapes or
articles, which are then subject to further processing to complete
the desired GTE component. Depending upon the initially-selected
alloy powder, it is not uncommon for HIP-based process flows to
require a relatively lengthy series of steps including casting,
cold compaction, can welding, the HIP process step itself,
de-canning, extruding, upset forging, final forging, and machining.
Each process steps adds duration, complexity, and tooling cost to
the manufacturing process; and, in many instances, incrementally
degrades the overall strength, ductility, and other desired
properties of the alloy material. For at least these reasons, the
aerospace industry has increasingly turned toward DMLS and other
DED powder fusion processes for the additive manufacture of many
GTE components.
[0015] During a generalized DMLS process, a laser or electron beam
is scanned across selected regions of a metallic powder bed to fuse
layers of metal powder and gradually build-up or compile a
component on a layer-by-layer basis. After selected regions of a
given metallic layer are fused in this manner, a new powder layer
is then applied over the recently-fused layer utilizing a
roller-based recoater system. This process of dispensing a metallic
powder layer, fusing selected regions of the powder layer, and then
applying a fresh metallic powder layer are repeated until
completion of the component. As compared to more conventional
powder metallurgy processes, such as HIP-based fabrication
processes of the type previously described, DMLS fabrication
processes generally require fewer processing steps and tooling
requirements and, thus, can be carried-out with greater efficiency
and at lower costs.
[0016] The foregoing benefits notwithstanding, DMLS and other DED
powder fusion processes remain limited in multiple respects. For
example, while more efficient than other legacy powder metallurgy
fabrication techniques, DMLS processes can still be undesirably
time consuming; current DMLS processes often require several hours
to complete components of relatively modest volumes and complexity.
Further, the components fabricated utilizing DMLS processes may
have undesirably high porosities. DMLS processes also tend to
modify powder microstructures due to the localized fusion
temperatures involved. It can consequently be difficult, if not
impractical to fabricate components from certain materials
utilizing DMLS processes. In particular, DMLS processes may be
poorly suited for producing components from certain non-equilibrium
alloy powders (described below), while reliably maintaining or
creating a desired microstructure throughout the component body;
e.g., a microstructure that is substantially free of deleterious
phases or participate growth, which can detract from the strength,
ductility, and other desired properties of the completed component.
As a still further drawback, DMLS and other DED processes often
impose undesired limitations on maximum permissible size of the
articles produced utilizing such processes.
[0017] There thus exists an ongoing demand for methods for
fabricating engine components and other metallic articles, which
overcome the limitations associated with conventional powder
metallurgy manufacturing processes. Ideally, such methods would
enable the fabrication of articles with a reduced number of process
steps, with reduced tooling requirements, with minimal scrap loss,
with relatively low porosities, with reduced constraints on article
size, and at reduced manufacturing costs and manufacturing
schedules. Further, it would be desirable for such methods to
enable fabrication of articles from non-equilibrium alloy powders,
while substantially maintaining the desired material properties and
microstructure throughout the fabrication process. Embodiments of
such methods are set-forth herein, as are other related methods and
articles produced in accordance with such methods. Other desirable
features and characteristics of embodiments of the present
invention will become apparent from the subsequent Detailed
Description and the appended Claims, taken in conjunction with the
accompanying drawings and the foregoing Background.
BRIEF SUMMARY
[0018] Methods for producing NEA feedstock powders utilized in AM
cold spray processes are disclosed, as are methods for fabricating
articles from such NEA feedstock powders utilizing
computer-controlled, AM cold spray processes. In various
embodiments, the method includes the step or process of purchasing,
producing, or otherwise obtaining an NEA feedstock powder, which is
composed of an alloy matrix throughout which a first minority
constituent is dispersed. Due to the metastable or non-equilibrium
state of the feedstock powder, the first minority constituent
precipitates from the alloy matrix when the NEA feedstock powder is
exposed to temperatures exceeding a critical temperature threshold
(T.sub.CRITICAL) for a predetermined time period. An AM cold spray
process is carried-out to fabricate a near-net article from the NEA
feedstock powder, which is exposed to a maximum temperature
(T.sub.SPRAY.sub._.sub.MAX) during the cold spray process. The
near-net article is then further processed to yield a finished
article. To preserve the metastable or non-equilibrium state of the
feedstock powder, T.sub.SPRAY.sub._.sub.MAX is maintained below
T.sub.CRITICAL through the cold spray process.
[0019] In other embodiments, the method includes the steps or
processes of forming a molten alloy into a solid NEA body, such as
an NEA ribbon or other bulk shape, utilizing a casting process
having a cooling rate equal to or greater than approximately
1.times.10.sup.6.degree. C./s. After casting, the solid NEA body is
mechanically converted into a NEA feedstock powder. An annealing
process is then performed during which the feedstock powder is
exposed to a maximum anneal temperature
(T.sub.ANNEAL.sub._.sub.MAX) for a predetermined time period. The
NEA feedstock powder is composed of an alloy matrix having a melt
point (T.sub.ALLOY.sub._.sub.MP) and throughout which a first
minority constituent is dispersed or distributed. The first
minority constituent precipitates from the alloy matrix when the
NEA feedstock powder is exposed to temperatures exceeding a
critical temperature threshold T.sub.CRITICAL for a predetermined
time period. The NEA body is formulated such that T.sub.CRITICAL is
less than T.sub.ALLOY.sub._.sub.MP and greater than
T.sub.ANNEAL.sub._.sub.MAX.
[0020] In yet further embodiments, the method includes the step or
process of utilizing an AM cold spray process to fabricate a
near-net article from a NEA feedstock powder having a melt point of
T.sub.ALLOY.sub._.sub.MP. The NEA feedstock powder contains an
aluminum alloy matrix and a non-trace amount of silicon contained
in the aluminum alloy matrix and precipitating therefrom when the
NEA feedstock powder is exposed to temperatures exceeding a
critical temperature threshold (T.sub.CRITICAL) for a predetermined
time period. The near-net article is further annealed at a maximum
annealing temperature (T.sub.ANNEAL). The method is carried-out
such that
T.sub.ANNEAL<T.sub.CRITICAL<T.sub.ALLOY.sub._.sub.MP; and,
perhaps, such that T.sub.ANNEAL.sub._.sub.MAX is greater than
T.sub.CRITICAL minus 150.degree. C. and less than T.sub.CRITICAL
minus 25.degree. C. In certain embodiments, the method further
comprises selecting the NEA feedstock powder to further contain a
non-trace amount of iron, which is also present in the aluminum
alloy matrix and which precipitates therefrom when the NEA
feedstock powder is exposed to temperatures exceeding
T.sub.CRITICAL for the predetermined time period.
[0021] The foregoing summaries are provided by way of non-limiting
example only. Various additional examples, aspects, and other
features of embodiments of the present disclosure are described in
more detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] At least one example of the present invention will
hereinafter be described in conjunction with the following figures,
wherein like numerals denote like elements, and:
[0023] FIG. 1 is a flowchart of an exemplary method for producing
NEA feedstock powders and for fabricating articles from such NEA
feedstock powders deposited utilizing computer-controlled, AM cold
spray processes;
[0024] FIG. 2 is a schematic illustrating an exemplary planar flow
casting process suitable for producing a solid NEA body or bulk
shape (here, an NEA ribbon), which may be further processed into a
NEA feedstock powder in accordance with the method of FIG. 1;
[0025] FIG. 3 is an SEM image of an NEA feedstock powder composed
of flake-shaped particles, which may be produced by mechanically
processing the NEA ribbon shown in FIG. 2 in an embodiment of the
present disclosure; and
[0026] FIG. 4 is a schematic illustrating an exemplary AM cold
spray process suitable for producing a near-net article, such as a
partially-completed aerospace component, from the NEA feedstock
powder produced in accordance with the method of FIG. 1.
[0027] For simplicity and clarity of illustration, descriptions and
details of well-known features and techniques may be omitted to
avoid unnecessarily obscuring the exemplary and non-limiting
embodiments of the invention described in the subsequent Detailed
Description. It should further be understood that features or
elements appearing in the accompanying figures are not necessarily
drawn to scale unless otherwise stated. For example, the dimensions
of certain elements or regions in the figures may be exaggerated
relative to other elements or regions to improve understanding of
embodiments of the invention.
DETAILED DESCRIPTION
[0028] The following Detailed Description is merely exemplary in
nature and is not intended to limit the invention or the
application and uses of the invention. Furthermore, there is no
intention to be bound by any theory presented in the preceding
Background or the following Detailed Description.
Definitions
[0029] As appearing herein, the term "alloy" refers to a material
composed predominately or exclusively of metallic constituents by
weight percent (wt %). As further appearing herein, a
"non-equilibrium alloy" or "NEA" is defined as a material
containing an alloy matrix throughout which one or more minority
constituents (metallic or non-metallic constituents present in
quantities less than that of the alloy matrix, by wt %) are
distributed. Further, the minority constitution(s) exhibit a
tendency or propensity, as predicted by established thermodynamic
principles, to precipitate from the matrix and agglomerate if the
NEA material is heated above a critical temperature threshold
(herein, "T.sub.CRITICAL") for an extended period of time on the
order of, for example, one minute. Thus, in essence, NEA materials
exist in desired metastable states; and, if heated to undesirably
high temperatures, the NEA materials will experience undesired
precipitate growth detracting from the overall strength, ductility,
and, perhaps, other desirable properties of the material. The value
of T.sub.CRITICAL will vary amongst embodiments depending upon
alloy composition, but will generally be less than the melt point
of the NEA material and, more specifically, the alloy matrix
(herein, "T.sub.ALLOY.sub._.sub.MP"). In certain embodiments,
T.sub.CRITICAL will range from about 350.degree. C. to about
500.degree. C. or, perhaps, from about 400.degree. C. to about
450.degree. C. In other embodiments, T.sub.CRITICAL may be greater
than or less than the aforementioned range.
[0030] Overview
[0031] Methods for producing NEA feedstock powders for usage in
cold spray processes are disclosed, as are methods for fabricating
articles from NEA feedstock powders utilizing computer-controlled,
AM cold spray processes. By virtue of the below-described rapid
cool casting processes, the NEA feedstock powders are produced to
natively contain desired microstructures, which are metastable in
nature and desirably preserved throughout the remainder of the
article fabrication process, to the extent practical. Therefore, in
an effort to maintain the desired metastable microstructures of the
NEA materials throughout the fabrication process, thermal loading
of the NEA material is carefully regulated across all pertinent
process stages and through the usage of AM cold spray processes in
compiling or printing the desired component on a layer-by-layer
basis. Accordingly, during a given processing stage, the maximum or
peak processing temperatures to which the NEA materials are exposed
can be limited to below T.sub.CRITICAL, as may be the case during
the AM cold spray process. In this manner, the desired metastable
microstructures of the NEA material can be substantially preserved
to enhance the strength, ductility, and other desired properties of
the finished article.
[0032] By way of non-limiting example, embodiments of the
below-described methods are well-suited for producing or
fabricating components utilizing Al-based and nickel-based
(Ni-based) NEA feedstock powders; that is, feedstock powders
predominately composed of Al or Ni, by wt %. Al-based and Ni-based
alloys are presently employed to fabricate certain aerospace
articles, such as GTE components, utilizing fundamentally different
manufacturing approaches. For example, in one common approach, GTE
components (and, more generally, other aerospace and turbomachine
components) can be suitably produced from Al-based alloys utilizing
HIP-based fabrication techniques of the type previous described.
However, as noted in the foregoing section entitled "BACKGROUND,"
such HIP-based fabrication techniques commonly require a relatively
length series of process steps including casting, cold compaction,
HIPing, extrusion, and forging, along with various intervening
steps. Many, if not all of the aforementioned process steps require
specialized tooling and add cost, complexity, and duration to the
manufacturing process. Further, debits to material strength are
often experienced at each stage of processing with the possible
exception of forging, which may increase component strength in skin
region of a metallic article, rather than through an article's
bulk. Comparatively, the cold spray-based AM manufacturing
processes described herein (when paired with the usage of the
specialized NEA feedstock powders) can produce comparable aerospace
components with enhanced properties at a small fraction of the cost
(due, in substantial part, to decreased tooling requirements) and
at abbreviated production schedules on the order of one or more
days as opposed to weeks or months.
[0033] The cold spray-based AM manufacturing processes may provide
other advantages in addition to those listed above. For example,
embodiments of the below-described cold spray-based AM
manufacturing process can produce highly dense articles have low
porosities, such as porosities less than 1% by volume and, perhaps,
less than 0.5% by volume. Furthermore, embodiments of the cold
spray-based AM manufacturing process can also ease size constraints
imposed by other conventional additive powder metallurgy
fabrication techniques, such as DED powder fusion processes. Such
attributes are highly desirable in the aerospace industry and can
also benefit other industries in which metallic components or
articles of manufacture are desirably fabricated from NEA materials
of the type described herein. Exemplary processes for fabricating
aerospace components, as well as various other types of metallic
articles, utilizing such cold spray-based AM manufacturing
processes are described below in conjunction with FIGS. 1-4.
Description of Exemplary Processes
[0034] Turning now to FIG. 1, an exemplary method 10 for
fabricating NEA feedstock powders and for manufacturing articles
from such NEA feedstock powders utilizing AM cold spray-based
processes is presented. As can be seen, method 10 includes a number
of sequentially-performed process steps identified as STEPS 12, 14,
16, 18, 20, 22. STEPS 12, 14, 16 are carried-out as part of an
overarching sub-process 24 (herein, "PROCESS BLOCK 24"), while
STEPS 20, 22 are carried-out as a part of an overarching
sub-process 26 (herein, "PROCESS BLOCK 26"). The steps illustrated
in FIG. 1 and described below are provided by way of non-limiting
example only. In alternative embodiments, additional process steps
may be performed, certain steps may be omitted, and/or the
illustrated steps may be performed in alternative sequences. For
example, in alternative implementations of method 10, only those
steps performed in PROCESS BLOCK 24 may be carried-out to produce
an FEA feedstock powder, which may then be commercially marketed or
otherwise utilized. In other alternative implementations of method
10, the steps set-forth within PROCESS BLOCK 24 may not be
performed, in which case the entity performing STEP 18 (the
below-described AM cold spray process) may obtain the desired NEA
feedstock powder by purchase from a third party supplier. Other
modifications are also possible, with any number of entities
performing differing ones of STEPS 12, 14, 16, 18, 20, 22 depicted
in FIG. 1.
[0035] Method 10 commences with obtaining the NEA feedstock powder
for usage in the subsequently-performed AM cold spray process
(PROCESS BLOCK 24). As indicated above, the NEA feedstock powder
may be obtained by purchase from a third party supplier or by
independent production; that is, production by the same entity
performing STEP 18 of method 10 (the cold spray process itself)
and, perhaps, one or more of post-spray STEPS 18, 20, 22.
Regardless of the particular entity or entities responsible for
feedstock powder production, the NEA feedstock powder can be
produced utilizing the following generalized process steps, as
set-forth in accordance with an exemplary embodiment of the present
disclosure. First, as indicated in FIG. 1 at STEP 12 of method 10,
a molten source material may be converted into a desired solid form
utilizing, for example, a rapid cooling casting process. As
appearing herein, a casting process is considered "rapid cooling"
when having a cooling rate equal to or greater than
1.times.10.sup.6.degree. C./s. Notably, this cooling rate exceeds
those achievable utilizing many conventional processes including
atomization processes of the type traditionally employed to produce
cold spray feedstock powders. Indeed, such atomization processes
often achieve, at most, cooling rates approximately ten times less
rapid the above-mentioned threshold (e.g., cooling rates equal to
or less than approximately 1.times.10.sup.5.degree. C./s) and
approximately one hundred or more times less rapid than the
below-described planar flow casting process, which is
advantageously (although not necessarily) utilized to produce bulk
NEA material in embodiments of method 10.
[0036] In one approach, molten source material is formed into a
desired solid shape utilizing a planar flow casting process (also
referred to as a "melt-spin process") during STEP 12 of method 10.
An example of such a planar flow casting process is schematically
illustrated in FIG. 2. Referring briefly to this drawing figure, a
molten source material 28 is held within a crucible 30 having a
nozzle 32. The flow of molten source material 28 through nozzle 32
is regulated via the application of a controlled internal pressure,
as represented by arrow 34. This internal pressure can be
mechanically applied by, for example, a plunger. In other
embodiments, the internal pressure can be applied utilizing
pressurized air or a different pressurized gas, such as argon (Ar)
or another inert gas. The source material is maintained in a molten
state utilizing a suitable heat input, such as a laser or electron
beam similar to that utilized in electron beam vapor deposition
processes. Alternatively, as indicated in FIG. 2, the desired heat
input can be generated by at least one induction coil 36, which is
positioned around crucible 30. When appropriately energized,
induction coil 36 generates a variable magnetic field driving
inductive heating within molten source material 28 (if having a
sufficient iron (Fe) content or otherwise composed of a
ferromagnetic material) and/or within a structure in contact with
source material 28; e.g., the walls of crucible 30 if composed of a
ferromagnetic material. Induction coil 36 may be controlled to
regulate the temperature of molten source material 28, as desired,
which may be monitored utilizing a non-illustrated temperature
sensor.
[0037] Immediately following discharge through nozzle 32, molten
source material 28 contacts cooled wheel 38, which is rotated at a
relatively rapid rate. Wheel 38 is usefully cooled by active water
flow or in another manner. As material 28 contacts the outer
periphery of wheel 38, molten source material 28 rapidly cools,
solidifies, and is quickly cast from wheel 38 as a bulk NEA shape
and, specifically, as a melt-spun ribbon 40. The appearance and
dimensions of melt-spun ribbon 40 will vary amongst embodiments;
however, in many cases, melt-spun ribbon 40 may resemble a metallic
foil and have a thickness ranging from about 0.5 to about 5
millimeters (mm) and, perhaps, from about 1 and about 2 mm. The
width of ribbon 40 is somewhat arbitrary, but may range from about
10 to about 100 mm in an embodiment. In further embodiments, the
thickness and/or width of ribbon 40 may vary with respect to the
aforementioned ranges. Due to the relative thinness of melt-spun
ribbon 40, the cooled state of rotating wheel 38, and the manner in
which ribbon 40 is rapidly ejected from wheel 38, exceptionally
high cooling rates are achieved. Such cooling rates can approach or
exceed approximately 1.times.10.sup.7.degree. C./s in many
instances, which enables formation of melt-spun ribbon 40 as an NEA
material having a desired metastable microstructure, as described
herein. The temperatures to which molten source material 28 is
heated and the rotational rate of wheel 38 will vary amongst
embodiments of the planar flow casting process; however, by way of
example, source material 28 may be heated to temperatures
approaching or exceeding 1000.degree. C. in certain
implementations, while wheel 38 may be rotated at a rate sufficient
to cast-off ribbon 40 at a rate exceeding approximately 300 meters
per second.
[0038] By virtue of the formulation of molten source material 28
and the rapid solidification thereof, melt-spun ribbon 40 is
composed of an NEA material. As previously discussed, the NEA
materials exist in metastable states and possess tailored
microstructures, which are desirably preserved across all
subsequently-performed stages of method 10. The particular
composition of the NEA material will vary amongst embodiments, as
will the shape of the initially-produced bulk NEA material (here,
melt-spun ribbon 40). By definition, the NEA material contains at
least one minority constituent or dispersoid (as defined by wt %)
having a propensity, as predicted by established thermodynamic
principals, to precipitate from the alloy matrix (as formed by the
majority metallic constituent(s) of the NEA material) when the NEA
material is heated above its particular critical temperature
threshold (T.sub.CRITICAL) for an extended time period; the term
"extended" utilized in a relative sense, noting that a time period
of several seconds may be considered "extended" in certain
instances. In many cases, the NEA material will contain multiple
minority constituents or dispersoids (e.g., silicides or carbides)
distributed throughout the alloy matrix and prone to participate
growth or agglomeration under such overtemperature conditions.
[0039] Further discussion will now be provided in which the NEA
material is described as an Al-based NEA material; that is, an NEA
material containing Al as its predominate constituent by wt %. Such
Al-based NEA material can advantageously provide highly stable
microstructure at elevated operating temperatures; e.g.,
temperatures exceeding 350.degree. C. and, in certain cases, at
temperatures approaching or exceeding 425.degree. C. Al-based NEA
materials are consequently well-suited for usage in the production
of aerospace and engine components including, for example,
turbocharger components and components contained within GTEs. It is
emphasized, however, that the following description is provided by
way of non-limiting example only; and that the NEA material need
not be composed of an Al-based alloy in all embodiments. For
example, in further embodiment, the NEA material, may be composed
of Ni-based alloy or superalloy. Furthermore, and more generally,
the fabrication processes described in connection with method 10
(FIG. 1) are not limited to the production of any particular type
of component or article of manufacture unless otherwise specified
in the context of the appended Claims.
[0040] In an embodiments, molten source material 28 and melt-spun
ribbon 40 shown in FIG. 2 may be composed of an Al-based NEA
material. An Al-based NEA material may further contain lesser
amounts of other metallic constituents, such as Fe, and/or other
non-metallic constituents, such as silicon (Si), which precipitate
from the Al-matrix if exposed to overtemperatures conditions. In
this case, the Fe content may gradually precipitate from the
Al-matrix and form undesired phases, such as Fe.sub.3Al, within the
NEA material. So too may the Si precipitate from the Al-matrix and
contribute to needle-like dendritic growth within the Al-matrix.
Once formed, such undesirable phases tend to grow or agglomerate
and therefore worsen over time. In various embodiments, the
Al-based NEA feedstock powder may contain between 85 wt % and 90 wt
% Al, between 8 and 10 wt % Fe, between 1 wt % and 3 wt % Si,
between 1 wt % and 2 wt % vanadium (V), and lesser amounts of other
metallic or non-metallic constituents, such as oxygen (O), zinc
(Zn), titanium (Ti), chromium (Cr), and/or manganese (Mn). In such
embodiments, T.sub.ALLOY.sub._.sub.MP may exceed T.sub.CRITICAL by
at least 100.degree. C.; e.g., T.sub.ALLOY.sub._.sub.MP may range
from about 600.degree. C. to about 700.degree. C., while
T.sub.CRITICAL may range from about 400.degree. C. to about
450.degree. C. In one specific implementation, the Al-based NEA
feedstock powder is composed, in whole or in substantial part, of
an AA8009 aluminum alloy powder. In further embodiments, the NEA
feedstock powder may be predominately composed of an Al-based alloy
matrix or a Ni-based alloy matrix throughout which silicides,
carbides, and/or other dispersoid strengtheners are
distributed.
[0041] With continued reference to FIG. 1, method 10 next advances
to STEP 14 during which the newly-produced solid NEA body or bulk
shape (e.g., melt-spun ribbon 40 shown in FIG. 2) is mechanically
processed or converted into feedstock powder of a desired
particulate shape and size range. A non-exhaustive list of particle
shapes includes oblong, rod- or whisker-like, platelet or laminae,
and spherical shapes. To the extent practical, particle shape may
be tailored for relatively low aerodynamic drag to optimize
trajectory and velocity during the AM cold spray process
carried-out during STEP 18 of method 40. However, in many
instances, particle shape may be largely dictated by the
constraints of the mechanical processing techniques performed
during STEP 14. When melt-spun ribbon 40 is mechanically processed
into smaller pieces utilizing chopping, grinding, and/or milling
processes, the resulting pieces or particles will often have a
platelet or flake-like form. The desired particle size range of the
NEA feedstock powder will also vary amongst embodiments and may be
selected based upon a number of competing criteria. Such competing
criteria may include the parameters of the AM cold spray process,
the capabilities of the cold spray apparatus, and the general
desirability of maximizing particle velocity during cold spraying,
while reducing reduce the propensity of the NEA feedstock material
to explode and minimizing oxide content when the NEA feedstock
material is prone to oxidation.
[0042] Generally, as the average particle size increases, so too
does the oxide content within the cold spray-deposited NEA body due
to an increase in the ratio of exposed surface area to volume of
the powder particulates. Conversely, as the average particle size
decreases, explosivity tends to increase, while (somewhat
counter-intuitively) particle velocities tend to decrease during
the cold spray process. To balance these competing factors, the
bulk NEA body (e.g., melt-spun ribbon 40 shown in FIG. 2) may be
converted into a powder form predominately or substantially
exclusively possessing a particle size ranging from about 10
microns (.mu.m) to about 140 .mu.m and, preferably, from about 20
.mu.m to about 90 .mu.m in maximum dimension. Note the terms
"predominately" or "substantially exclusively" are utilized here to
indicate that a minor amount of smaller particles may remain within
the NEA feedstock powder as such particles may be difficult to
sieve or otherwise completely remove due to electrostatic
attraction to larger particles. In one embodiment, the NEA
feedstock powder produced pursuant to STEP 14 may contain or
consist substantially entirely of flake-shaped particles ranging
from approximately 10 .mu.m to approximately 90 .mu.m in maximum
dimension. This may be appreciated by referring briefly to FIG. 3,
which is an SEM image 42 of such flake-like particles or platelets
with a legend 44 included for scale. SEM image 42 thus depicts a
reduction to practice of NEA feedstock powder having a flake-like
form factor and dimensions within the range specified above. In
other embodiments, the NEA feedstock powder can posses different
geometries and dimensions; and/or may be mixed with other powders
or media to form a powder mixtures utilized during the
below-described AM cold spray process.
[0043] Various different mechanical processing steps can be
employed during STEP 14 to convert melt-spun ribbon 40 (FIG. 2)
into a NEA feedstock powder having the desired particle shape and
size range. As indicated above, mechanical processing steps for
converting large pieces of material into smaller pieces of material
include chopping, milling, grinding, and combinations thereof.
Processes for selecting a desired particle size range include
sieving, cyclonic separation, and the like. In one approach,
melt-spun ribbon 40 (FIG. 2) is first converted into flake-like
pieces utilizing a dry or wet chopping process. Sieving is then
performed to remove undesirably large pieces or "overs" of the NEA
material. Afterwards, attrition milling is carried-out to further
reduce the size of the flake-like pieces thereby bringing the
particles into closer conformance with the desired sized range.
Such an attrition milling process is generally performed with an
attritor unit, which utilizes a rod to aggressively stir the NEA
material along with a milling media, such as steel spheres.
Attrition milling can be carried-out in either a wet or dry state.
Notably, attrition milling processes have been found to produce
significantly higher yields than other milling process, such as a
ball milling. After attrition milling, additional grinding steps
and/or particle size selection steps can be performed, as needed.
Furthermore, in certain cases, additional steps may be performed
for particle-shaping purposes; e.g., to round the flake-like
particles into more spherical shapes to decrease aerodynamic drag
and instabilities during the subsequently-performed AM cold spray
process. The end result may be NEA feedstock powder, such as that
shown in FIG. 3, generally possessing a flake-shaped form factor
and desired dimensions.
[0044] Next, at STEP 16 of method 10, the NEA feedstock powder is
annealed. Such an annealing process (herein, a "pre-spray anneal")
is usefully performed to relieve material stress and any work
hardening resulting from the mechanical processing steps performed
during STEP 14 of method 10. When performed, the pre-spray anneal
may be carried-out in accordance with a pre-established heating
schedule specific to the NEA material being processed. Generally,
pre-spray annealing will entail heating the NEA feedstock powder to
a maximum anneal temperature (T.sub.ANNEAL.sub._.sub.MAX) for a
predetermined period of time on the order of, for example,
approximately one hour. The pre-spray annealing process is
controlled such that T.sub.ANNEAL.sub._.sub.MAX is less than
T.sub.CRITICAL throughout the annealing process. For example, in
one embodiment in which T.sub.CRITICAL ranges from 400.degree. C.
to 450.degree. C., T.sub.ANNEAL.sub._.sub.MAX may range from
350.degree. C. to 400.degree. C. In another embodiment,
T.sub.ANNEAL.sub._.sub.MAX may range between a minimum of
T.sub.CRITICAL minus about 150.degree. C. to a maximum of
T.sub.CRITICAL minus about 25.degree. C. or, perhaps, between a
minimum of T.sub.CRITICAL minus about 100.degree. C. to a maximum
of T.sub.CRITICAL minus about 50.degree. C. By relieving materials
stresses and possibly reducing work hardening (particularly in the
case of feedstock powders prone to work hardening, such as Al-based
NEA feedstock powders), the resulting NEA feedstock powder may be
rendered more malleable to enhance adhesion and compaction during
the subsequently-performed AM cold spray process. These benefits
notwithstanding, the NEA feedstock powder need not be subject to
pre-spray annealing in alternative embodiments of method 10.
[0045] Following STEP 16 of method 10 and the completion of PROCESS
BLOCK 24, the NEA feedstock powder has now been produced. Utilizing
the newly-produced NEA feedstock powder, an AM cold spray process
can be carried-out to additively manufacture or three dimensionally
print articles of manufacture having near-net shapes; that is,
shapes encompassing and generally approximately the desired final
geometries of the articles desirably produced pursuant to method
10. An exemplary embodiment of a suitable AM cold spray process
will now be described in conjunction with FIG. 4, which
schematically illustrates a cold spray apparatus 46 suitable for
performing STEP 18 of method 10. Cold spray apparatus 46 includes a
NEA feedstock powder supply 48, such as a hopper containing NEA
feedstock powder 50. A first flow line 52 connects a source of
pressurized carrier gas represented by arrow 54 to powder supply
48, while a second flow line 56 connects powder supply 48 to a cold
spray gun 58. The carrier gas can be, for example, air, helium,
nitrogen, or another gas that is preferably although
non-essentially inert. During operation of cold spray apparatus 46,
the pressurized gas supplied by gas source 54 is delivered to
powder supply 48, metered amounts of the NEA feedstock powder are
entrained in the gas stream, and the particle-entrained gas stream
is delivered to gun 58 for discharge through nozzle 60. Additional
velocity and controlled thermal input is further imparted to the
gas carrier stream and the entrained particles by preheating a
portion of the gas supplied by gas source 54. For example, as
indicated in the lower left corner of FIG. 4, a fraction of the gas
supply may be directed through a preheater unit 62 via flow line
64, delivered to cold spray gun 58 via flow line 66, and then mixed
with the particle-entrained gas stream within gun 58 prior to or
during discharge through nozzle 60.
[0046] The process parameters governing the AM cold spray process
will vary amongst embodiments, providing that the peak temperatures
to which the NEA feedstock powder is heated are maintained below
T.sub.CRITICAL through the cold spray process. In this regard, the
cold spray process may be performed such that the NEA feedstock
powder is exposed to a maximum processing temperature of
T.sub.SPRAY.sub._.sub.MAX, which is less than T.sub.CRITICAL and
may be at least 50.degree. C. less than T.sub.CRITICAL in an
embodiment. For completeness, it is noted that preheater unit 62
may heat the gas flow to temperatures exceeding T.sub.CRITICAL in
certain instances. Even when this is the case, however, the
temperature of the NEA feedstock powder remains below
T.sub.CRITICAL as the powder particles are entrained in the carrier
stream for an extremely brief time period, which prevents complete
heat transfer from the carrier gas to the powder particles.
Additionally, gas temperatures may decrease rapidly to levels below
T.sub.CRITICAL by the time the gas reaches cold spray gun 58 and
contacts the feedstock powder. Gas temperature will also generally
plummet upon discharge from nozzle 60 such that the cooling rate at
nozzle 60 may approach or exceed the above-mentioned threshold
(e.g., 1.times.10.sup.6.degree. C./s) in embodiments. Finally,
while a certain amount of thermal input will be reintroduced into
the NEA feedstock powder due to the conversion of kinetic energy
when contacting the target surface or site-of-deposition, this
secondary heating mechanism will also typically be insufficient to
heat the NEA feedstock powder (or the resulting compacted body
composed of the NEA material) to temperatures exceeding
T.sub.CRITICAL. Regarding the other process parameters of the AM
cold spray process (e.g., deposition rates, particle discharge
velocities, carrier gas types, chamber environment conditions, and
the like), again such parameters will vary amongst embodiments. In
one embodiment, helium is utilized as the carrier gas, which is
supplied at a pressure approaching or exceeding approximately 700
pounds per square inch to impart the particles with high velocities
and relatively straight trajectories when discharged from cold
spray gun 58.
[0047] As generically indicated on the right side of FIG. 4, the AM
cold spray process may be utilized to gradually compile or build-up
a near-net article 68 on a layer-by-layer basis. Near-net article
68 is generically illustrated in FIG. 4 in an arbitrary orientation
and supported by a platform 70. During the cold spray process, cold
spray gun 58 is moved relative to near-net article 68 in some
fashion, whether by movement of cold spray gun 58, by movement of
platform 70, or a combination thereof. In one approach, as
generically represented by block 74 and multidirectional arrow
graphic 76 in FIG. 4, a computer-controlled robotic arm may be
utilized to move cold spray gun 58 along all three orthogonal axis
to deposit the NEA feedstock powder at selected locations and
gradually build the desired part. The movement of cold spray gun 58
is dictated by computer-readable design data of any suitable file
type, such as SLA extension-type files. In many embodiments, the
part design data will assume the form of one or more Computer Aided
Design (CAD) files, which may be generated by a part designer
utilizing a commercially-available CAD program products. A
non-exhaustive list of such commercially-available CAD program
products includes TOPSOLID, CATIA, CREO, AUTODESK INVENTOR,
SOLIDWORKS, and NX CAD software packages. Finally, if desired, one
or more sacrificial structures 72 can be embedded in the near-net
article 68 during the AM cold spray process; and subsequently
removed to form lightening voids, internal cavities, flow passages,
or the like within near-net article 68, as discussed more fully
below in conjunction with STEP 22 of method 10.
[0048] When striking the target surface or site-of-deposition,
kinetic energy of the particle impact induces plastic deformation
of the cold spray-deposited NEA material to create the desired bond
between layers of the deposited NEA feedstock powder. As indicated
by the "cold spray," generally considered, the particles are
applied at a temperature well below their melt point such that the
kinetic energy of the particles on impact (rather than particle
temperature) is the mechanism underlying plastic deformation and
bonding of the particle with the target surface. Advantageously, AM
cold spray processes are capable of relatively rapid deposition
rates often exceeding 1 gram of material per second. As a result,
the AM cold spray process carried-out at STEP 18 of method 10 may
be capable of producing a part in a highly efficient manner; e.g.,
the cold spray process may be capable of producing a component of
modest volume and complexity in several minutes, while a DMLS
process may require several hours to fabricate a comparable
component. Furthermore, as each layer of NEA feedstock powder is
deposited by cold spray, the newly-applied layer tends to compact
and thereby densify the previously-deposited NEA material layers.
This, combined with the desirable properties of the NEA feedstock
powder, enable the AM cold spray process to fabricate near-net
articles having low porosities, which may be less than 1% and,
perhaps, less than 0.5% by volume.
[0049] After completion of the AM cold spray process, additional
process steps may be performed to transform the near-net article(s)
into the finished article(s) of manufacture, as indicated in
PROCESS BLOCK 26 of FIG. 1. For example, referring to STEP 20 of
method 10, a post-spray annealing process may be performed during
which the near-net article is subject to elevated temperatures for
a predetermined time period. The post-spray annealing process may
be similar or substantially identical to the pre-spray annealing
process performed during STEP 16 in implementations of method 10.
Accordingly, the near-net article may be heated to a maximum anneal
temperature (T.sub.ANNEAL.sub._.sub.MAX) for a predetermined period
of time on the order of an hour. The post-spray annealing process
is controlled such that T.sub.ANNEAL.sub._.sub.MAX is less than
T.sub.CRITICAL; e.g., when T.sub.CRITICAL ranges from 400.degree.
C. to 450.degree. C., T.sub.ANNEAL.sub._.sub.MAX may range from
350.degree. C. to 400.degree. C. in an embodiment. In other
embodiments, the post-spray annealing process is controlled such
T.sub.ANNEAL is greater than 1/2 T.sub.CRITICAL and less than
T.sub.CRITICAL. Such a post-spray annealing process can be
performed to reduce the compression stress within the NEA material
resulting from the cold spray process. Machining may then be
performed during STEP 22 of method 10 to refine surface finishes,
to bring final dimensions into close tolerance with design
dimensions, and/or to define refined or detailed structure features
of the finished article. By performing the post-spray annealing
prior to such machining, undesired dimensional changes occurring
after final machining can be minimized or entirely avoided.
[0050] Finally, if any sacrificial bodies or fugacious tooling
structures are present within the near net article, such
sacrificial tooling may be removed during STEP 22 of method 10.
Suitable removal techniques will depend upon the composition of the
NEA article produced pursuant to method 10 as compared to the
composition of the sacrificial structures. Generally, chemical
dissolution (including acid leeching in the case of mild steels),
breaking in the case of brittle (e.g., ceramic) materials, and
Coefficient of Thermal Expansion (CTE) mismatch techniques can be
employed. Collapsible and removable tooling can also be utilized to
form desired internal voids, chambers, or flow passages within the
additively-manufactured articles. For example, and referring
briefly again to FIG. 4, sacrificial structure 72 can be removed
from article 68 (e.g., by etching or chemical dissolution) to
create a flow passage therethrough or a cavity therein. This may be
beneficial in implementations in which the completed article
assumes the form of a GTE component, such as a flowbody or actuator
housing. For example, in one embodiment, the completed article may
be realized as a valve flowbody through which a flow passage
extends, as generically represented in FIG. 4. Thus, in such an
embodiment, near-net article 68 can be processed during PROCESS
BLOCK 26 to yield a GTE valve flowbody (or actuator housing)
composed of an Al-based or Ni-based NEA material and having a flow
passage extending therethrough. Embodiments of method 40
advantageously enable fabrication of such a GTE valve flowbody (or
actuator housing) from materials having high stabilities at
elevated temperatures exceeding 260.degree. C. and, perhaps,
temperatures approaching or exceeding 350.degree. C. In further
embodiments, method 40 (and variations thereof) can be utilized to
fabricate other types of aerospace components, including airborne
valves and heat exchangers, as well as various other types of
components or metallic articles subject to elevated temperatures
during usage including engine components and turbomachine (e.g.,
turbocharger) components generally.
CONCLUSION
[0051] There has thus been provided methods for the production of
NEA feedstock powders of the type utilized in cold spray processes,
as well as methods for fabricating articles utilizing such NEA
feedstock powders and computer-controlled, AM cold spray processes.
Embodiments of the above-described methods enable the production of
completed parts with desirable NEA microstructures characterized by
enhanced material strength, ductilities, low porosities, and other
desirable properties. Embodiments of the below-described methods
are well-suited for producing or fabricating components utilizing
Al-based NEA feedstock powders, although by no means limited to
such feedstock powders. Embodiments of the cold spray-based AM
manufacturing processes described herein (when paired with the
usage of the specialized NEA feedstock powders) can be utilized to
produce components with such enhanced properties, while decreasing
tooling requirements, in more abbreviated time periods (e.g., on
the order of a few days), with fewer processing steps, at lower
scrap volumes, and while easing article size constraints imposed by
other conventional DED powder fusion processes. The end result is a
vastly improved AM production process featuring cost and time
savings, which are highly desirable with the aerospace industry and
across other industries. Furthermore, parts or articles produced
utilizing the AM cold spray processes described herein can be
distinguished from other components utilizing known inspection
techniques, such as photomicrographs of the NEA material structurer
revealing splat boundaries created during the cold spray
process.
[0052] In one embodiments, the above-described method includes the
steps or processes of forming a molten alloy into a solid NEA body,
such as an NEA ribbon or other bulk shape, utilizing a casting
process having a cooling rate equal to or greater than
approximately 1.times.10.sup.6.degree. C./s and, perhaps, cooling
rate equal to or greater than 1.times.10.sup.7.degree. C./s. After
casting, the solid NEA body is mechanically converted into a NEA
feedstock powder. An annealing process is then performed during
which the feedstock powder is exposed to a maximum anneal
temperature (T.sub.ANNEAL.sub._.sub.MAX) for a predetermined time
period. The NEA feedstock powder is composed of an alloy matrix
having a melt point (T.sub.ALLOY.sub._.sub.MP) and throughout which
a first minority constituent is dispersed or distributed. The first
minority constituent precipitates from the alloy matrix when the
NEA feedstock powder is exposed to temperatures exceeding a
critical temperature threshold T.sub.CRITICAL for a predetermined
time period. The NEA body is formulated such that T.sub.CRITICAL is
less than T.sub.ALLOY.sub._.sub.MP and greater than
T.sub.ANNEAL.sub._.sub.MAX. In certain embodiments, the NEA
feedstock powder may be formulated such that the NEA feedstock
powder is predominately composed of a first material by weight
percent, the first material selected from the group consisting of
aluminum and nickel; and the first minority constituent forms
dispersoids within the NEA feedstock powder, the dispersoids
selected from the group consisting of silicide dispersoids and
carbide dispersoids.
[0053] While at least one exemplary embodiment has been presented
in the foregoing Detailed Description, it should be appreciated
that a vast number of variations exist. It should also be
appreciated that the exemplary embodiment or exemplary embodiments
are only examples, and are not intended to limit the scope,
applicability, or configuration of the invention in any way.
Rather, the foregoing Detailed Description will provide those
skilled in the art with a convenient road map for implementing an
exemplary embodiment of the invention. It being understood that
various changes may be made in the function and arrangement of
elements described in an exemplary embodiment without departing
from the scope of the invention as set-forth in the appended
claims.
* * * * *