|
Source |
Author(s) |
Title/Abstract |
|
ITSC2006 |
A.C. Hall |
Mechanisms Resulting in Improved Ductility of Cold Spray
Coatings After Annealing |
|
|
R.L. Williamson |
An earlier study reported an investigation
of the mechanical properties of cold sprayed
aluminum and the effect of annealing on
those properties [1]. In that study, cold
spray coatings approximately one centimeter
thick were prepared using three different
feedstock powders: Valimet H-10, Valimet
H-20, and Brodmann Flomaster. ASTM E8
tensile specimens were machined from these
coatings. Each material was tested in two
conditions: as-sprayed and after a 300°C, 22
hour air anneal. The as-sprayed material
showed a high ultimate strength and low
ductility, < 1% elongation. The annealed
samples showed a reduction in the ultimate
strength but a dramatic increase in
ductility, up to 10% elongation.
Microstructural examinations and
fractography clearly showed a change in the
fracture mechanism between the as-sprayed
and annealed material, but insufficient data
was available to conclusively explain the
ductility increase at that time. Since then,
Kikuchi mapping of the Valimet H-10 material
in the as-sprayed and annealed conditions
has been conducted. Kikuchi mapping allows
indexing of grains, identification of grain
boundaries, and phase identification using
backscattered diffraction patterns in an SEM
[2]. The data shows that significant
recrystallization within the splats upon
annealing has occurred. No significant
crystal growth across splat boundaries is
observed. The data demonstrate that the
mechanism of ductility increase in annealed
cold spray deposits is recrystallization of
the base aluminum material. |
|
D.A. Hirschfeld |
|
T.J. Roemer |
|
ITSC2006 |
B. Jodoin |
Cold Spray Deposition of Metastable Alloys |
|
|
L. Ajdelsztajn |
The proposed work describes recent efforts
to develop metastable Al-Fe-V-Si coatings
for internal-combustion engine applications
with higher mechanical properties at high
operating temperatures. To do so, the
metastable solid powder alloy was engineered
from rapid solidification technique (namely
gas atomization). The metastable alloy
powder was deposited using the Cold Spray
process in order to produce protective
coatings on top of existing parts. The
critical velocity, above which Cold Spray
deposition takes place, was successfully
achieved and Al-Fe-V-Si coatings were
produced. The microstructure of the
feedstock powder was retained in the
coatings produced, showing the potential of
the Cold Spray process to produce metastable
coatings for internal combustion engine
applications. |
|
G. Bérubé |
|
J. Villafuerte |
|
ITSC2006 |
H. Kreye |
The Cold Spray Process and Its Optimization |
|
|
T. Schmidt |
Cold gas spraying is a coating process by
which coatings can be produced without
significant heating of the sprayed powder.
In contrast to the well-established thermal
spray processes such as flame, arc and
plasma spraying, in cold spraying there is
no melting of particles prior to impact on
the substrate. Bonding occurs when the
impact velocities of the particle exceed a
critical value. This critical velocity
depends not only on the type of the spray
material, but also on the powder quality,
the particle size and the particle impact
temperature. The present contribution
summarizes general views and reports recent
developments with respect to the
understanding of the process and respective
consequences for the optimization of the
process. The presented optimization
procedure covers principles to increase gas
and particle velocities and rules to
decrease the critical velocity for bonding.
By consequently following such route for
typical metallic spray materials, cold
spraying as a quite new coating technique is
already capable to provide coating qualities
very similar to those of work hardened bulk
material at powder feed rates similar to
those of thermal spraying and deposition
efficiencies of about 90%. |
|
F. Gärtner |
|
T. Stoltenhoff |
|
ITSC2006 |
T. Schmidt |
New Developments in Cold Spray Based on Higher Gas and
Particle Temperatures |
|
|
F. Gaertner |
In cold spraying, bonding is associated with
shear instabilities caused by high strain
rate deformation during the impact. It is
well known, that bonding occurs, when the
impact velocity of an impacting particle
exceeds a critical value. This critical
velocity depends not only on the type of
spray material, but also on the powder
quality, the particle size and the particle
impact temperature. Up to now, optimization
of cold spraying mainly focused on
increasing the particle velocity. The new
approach presented in this contribution
demonstrates capabilities to reduce critical
velocities by well-tuned powder sizes and
particle impact temperatures. A newly
designed temperature control unit was
implemented to a conventional cold spray
system and various spray experiments with
different powder size cuts were performed to
verify results from calculations.
Microstructures and mechanical strength of
coatings demonstrate that the coating
quality can be significantly improved by
using well-tuned powder sizes and higher
process gas temperatures. The presented
optimization strategy, using copper as an
example, can be transferred to a variety of
spray materials and thus, should boost the
development of the cold spray technology
with respect to the coating quality. |
|
H. Kreye |
|
ITSC2006 |
H. Fukanuma |
The Influence of Particle Morphology on In-flight Particle
Velocity in Cold Spray |
|
|
N. Ohno |
Cold spray is a relatively recent spray
coating technology in which metal or alloy
particles are plastically deformed by the
kinetic energy of the particles accelerated
in a supersonic gas flow through a
convergent-divergent nozzle before hitting
the substrate. The particle velocity at
impact onto the substrate is a key factor in
determining the characteristics of the cold
spray deposit. Therefore, various studies
have been carried out on particle
acceleration with the aim of obtaining
faster cold spray particle velocities.
Mathematical modeling has also been carried
out on spherical particle acceleration in a
supersonic gas flow in a Laval nozzle. To
understand better how a non-spherical
particle behaves in a supersonic gas flow,
experiments were carried out on the affect
of morphology on particle acceleration in
cold spray. Two types of powder morphology
were used for the experiment, one was
spherical and the other was angular and
jagged. The particle size distributions were
almost the same. In-flight particle
velocities of the spherical and angular
particles were measured with a DPV-2000. It
was found that the particle morphology
greatly influenced the in-flight particle
velocity and deposit efficiency. |
|
B. Sun |
|
R. Huang |
|
ITSC2006 |
D. Helfritch |
Optimal Particle Szie for the Cold Spray Process |
|
|
V. Champagne |
The importance of high velocity for good
particle deposition efficiency in the cold
spray process is well known. Small particles
achieve high velocities during nozzle
acceleration, but also decelerate rapidly in
the flow downstream of the bow shock wave.
This study examines the effect of particle
size on velocity and deposition efficiency
in the cold spray process by means of flow
modeling and gas-particle dynamics. Particle
trajectories are modeled from the nozzle
chamber to the impact with the substrate.
Optimum particle size is identified for
various particle characteristics and spray
configurations. |
|
ITSC2006 |
L. Aidelsztain |
Cold Gas Dynamic Spraying of Fe-based Amorphous Alloy |
|
|
E. J. Lavernia |
This paper describes recent effort to
synthesize Fe-based amorphous alloys
coatings using Cold Gas Dynamic Spraying.
Characterization of the gas atomized
Fe-based (Fe-Cr-Mo-W-C-Mn-Si-Zr-B) powder
shows that fully amorphous powder is found
when particle diameter is below 20 µm. The
coatings produced were composed of the same
microstructure as the one observed in the
feedstock powder. The overall deformation
suggests the occurrence of a localized
deformation process at the particle/particle
boundary and possible adiabatic deformation
softening inside the powder particles during
splat formation. The influence of the
substrate material on the coating deposition
process was also investigated. The synthesis
of fully amorphous, porous free coatings
using Cold Spray was demonstrated in this
work. |
|
B. Jodoin |
|
P. Richer |
|
E. Sansoucy |
|
ITSC2006 |
J. Haynes |
Cold Sprayed Discontinuously Reinforced Aluminum (DRA) |
|
|
A. Pandey |
Discontinuously reinforced aluminum (DRA)
has many attractive mechanical and physical
properties. Discrete hard particles such as
B4C have been added to aluminum alloys, such
as 6061, to add strength and stiffness for
an improved performance. Traditionally,
these particles are introduced in melt
additions and extruded or made into preforms
and cast. These ceramic particles are also
added in aluminum through a powder
metallurgy process resulting in extrusion or
forging. Inhomogeneous distribution of these
particles in casting results in inferior
properties and also it is difficult to
produce preforms with high volume fraction
materials. While wrought properties can be
achieved in the powder metallurgy approach,
extrusion directionality of the process
introduces anisotropic properties. Though
thermal spray has been used to produce DRA
coatings, it has been observed that the
melting and re-solidification of the
aluminum matrix material as well as reaction
with potential substrates such as copper is
of concern. Since cold spray does not melt
the feedstock material, it is ideally
suitable for producing DRA coatings. Boron
carbide particles and 6061 aluminum alloy
were used as reinforcing and matrix material
respectively. Experimental studies were
carried out to optimize the raw material
characteris tics, DRA powder preparation
technique and spray parameters, and using
these optimized parameters, dense and strong
coatings and free-forms were produced.
Proper selection of the particle size
distribution of the matrix and reinforcing
materials, wet blending them and subsequent
drying yielded the required spray feedstock.
Optimization of the spray parameters
resulted in strong, dense and well-bonded
coatings with acceptable deposition
efficiency and deposition rate values. Post
spray heat treatments were carried out to
retrieve the ductility of the specimens. A
series of mechanical property measurements
were carried out on the as -sprayed and heat
treated specimens. Results of these studies
were analyzed to evolve a preliminary model
of the DRA structures and establish the
feasibility of cold spray production of DRA
coatings and free-form structures. |
|
J. Karthikeyan |
|
A. Kay |
|
ITSC2006 |
R. Gr. Maev |
Structure Formation of Ni-based Composite Coatings During
Low Pressure Gas Dynamic Spraying |
|
|
V. Leshchynsky |
The response of Ni-SiC powders deposited by
Gas Dynamic Spraying (GDS) with various
particle velocities, and their compaction
behavior to the different packing densities
were studied in parallel. Bulk compacts
(90–99% dense), made in the form of 6 mm
diameter by 3 mm thick disks, were analyzed
to determine the structural changes
occurring within the particles and at the
particle boundaries, and to examine their
mechanical properties. Optical microscopy
and SEM observations revealed the presence
of a lamellar morphology and a strong
interparticle bonding in the composite
coating. An analysis of the experimental
data revealed the retention of the nanoscale
structure and a localized grain refinement.
Adiabatic shear band areas were observed and
thought to be responsible for the grain
refinement. Powder layers, which were shear
compacted to the packing density (up to 90%
dense), showed the best densification
characteristics. Correspondingly, coatings
with enhanced mechanical properties and a
strong exchange coupling between hard and
soft phases are obtained. |
|
A. Papyrin |
|
ITSC2006 |
M. Beneteau |
Gas Dynamic Spray Composite Coatings for Iron and Steel
Castings |
|
|
W. Birtch |
The present study was carried out to
evaluate the applicability of the Gas
Dynamic Spraying (GDS) of different powder
compositions for depositing wear-resistant
composite coatings on iron and steel
castings. This process, simply known as
“cold spray,” utilizes the kinetic energy of
particles sprayed at supersonic velocities
to produce a bonding of the particles to the
substrate. Ni and Cu based coatings
containing W, Zn and TiC as reinforcement
were made by the low pressure GDS technique
and investigated. The coatings
microstructures were studied by both optical
and scanning electron microscopy. Phase
composition, hardness and wear resistance of
the GDS coatings were analyzed. The
ball-on-disc sliding wear test was used for
assessing the wear resistance
characteristics of the coatings using a
ceramic (Si3N4) ball. W and TiC reinforced
coatings showed the best wear performance.
These were further evaluated in greater
detail. In addition to the obtained test
results, the application prospects for such
GDS coatings were discussed. |
|
J. Villafuerte |
|
J. Paille |
|
M. Petrocik |
|
R. Gr. Maev |
|
E. Strumban |
|
V. Leshchynsky |
|
ITSC2006 |
H. Weinert |
Low Pressure Gas Dynamic Spray Forming Near-net Shape
Parts |
|
|
E. Maeva |
Thermal spraying processes are well known in
industry for providing relatively dense
components. The Gas Dynamic Spray (GDS)
technologies are a growing alternative,
especially after the great success of
certain applications such as plasma and
thermal spray formed components. One of the
advantages of GDS is the possibility to
obtain complex thin-walled shapes of various
powder materials and composites. The
optional post-spraying processes such as
sintering, sizing and little machining may
be applied. Using the low pressure radial
injection GDS method, some new thin wall
components have been formed. The process
involves the automatic mechanical removal of
sprayed ring components from a mould. Both
the structure and properties of powdered
material along with the GDS technology
itself were studied. The main spraying and
mould parameters were found to achieve high
durability of moulds, which allowed the
realization of a large scale GDS forming
technology. |
|
V. Leshchynsky |
|
ITSC2006 |
T. Van Steenkiste |
Kinetic Sprayed Rare Earth Iron Alloy Composite Coatings |
|
|
|
One of the unique advantages of the kinetic
spray process is its ability to mix
constituents that would normally react with
each other to form coatings. We have used
this attribute to produce composite coatings
with different rare earth iron alloys
(REFe2) and several ductile matrices.
Composite coatings of Terfenol-D
((Tb0.3Dy0.7)Fe1.9) and SmFe2 were combined
with ductile matrices of aluminum, copper,
iron, molybdenum, tantalum, and nickel.
Evidence of an induced magnetic coercivity
was measured for the REFe2- Mo and Fe
composite coatings. Coatings were produced
on flat substrates and shafts. Coating
morphology as well as the physical,
magnetostrictive and magnetic properties of
these coatings will be discussed. |
|
ITSC2006 |
E. Sansoucy |
Effect of Spraying Parameters on the Microstructure and
Bond Strength of Cold Spray Aluminum Alloy
Coatings |
|
|
B. Jodoin |
Aluminum alloy powders of different
compositions and phases, Al/B4C, Al-Co-Ce,
and Al 5083, were sprayed using the Cold
Spray deposition process. The resulting
coatings and the effects of several process
parameters were evaluated using scanning
electron microscopy and bond strength tests.
The results show that the bond strengths
depend on the powder composition but do not
vary significantly with the powder feed
rate. Adhesion strength values were obtained
for Al/B4C and Al 5083 coatings. The
Al-Co-Ce coatings failed at the
coating-adhesive interface, indicating a
superior adhesion strength than what was
achieved in the bond strength tests. |
|
P. Richer |
|
L. Ajdelsztajn |
|
ITSC2006 |
T.S. Price |
The Effect of Cold Spray Deposition on a titanium Coating
on the Fatigue Behaviour of a Titanium Alloy |
|
|
P.H. Shipway |
The deposition of titanium on a titanium
alloy substrate is being examined for
potential use as a surface treatment for
medical prostheses. A Ti6Al4V alloy was
coated with pure titanium by cold gas
dynamic spraying (CGDS). Coatings were
deposited onto samples with two different
surface preparation methods (as-received and
grit blasted). The fatigue life of the
as-received and grit blasted materials, both
before and following coating, was measured
with a rotating-bend fatigue rig. An 18%
reduction in fatigue life was observed
following the application of the coating to
the as-received substrate, but no
significant reduction was observed on its
application to the grit blasted substrate.
The reduction in fatigue life has been
related to the substrate-coating interface
properties and residual stress states. |
|
D.G. McCartney |
|
ITSC2006 |
H.T. Wang |
Formation of Fe-Al Intermetallic Compound Coating Through
Cold Spraying |
|
|
C.J. Li |
Intermetallic materials have excellent high
temperature oxidation resistance and
erosion, cavitation resistances and are
promising coating materials with many
potential industrial applications. In this
study, the formation of Fe-Al intermetallic
compound-based coating was performed by cold
spraying assisted by a post-annealing
treatment. Fe-Al alloy composite powder
containing 20wt% WC-Co was produced by ball
milling process. Nano-structured Fe-Al alloy
coating was deposited through cold spraying.
The coating was annealed at different
temperatures. The microstructure of the
coating was characterized by scanning
electron microscopy, optical microscopy and
x-ray diffraction analysis. It was found
that the microstructure of the as-sprayed
coating depended significantly on the
microstructure of the powder. A Fe-Al
intermetallic phase was formed during the
annealing at a temperature higher than
500°C. Moreover, grain growth occurred with
the increase of the annealing temperature.
The results showed that the microhardness of
the as-sprayed coating reached 600HV and
more. The effect of the annealing treatment
on the coating microstructure and hardness
was examined. |
|
G.J. Yang |
|
C.X. Li |
|
ITSC2006 |
H. Mäkinen |
Mechanical Properties and Corrosion Resistance of Cold
Sprayed Coatings |
|
|
J. Lagerbom |
Cold spraying is quite a new process, which
is an effective method to deposit dense and
pure coatings. The aim of this study was to
investigate microstructures and mechanical
properties (hardness and adhesion) of the
cold sprayed coatings. The coating materials
were aluminium, copper, nickel and zinc. The
substrate materials were carbon steel and
copper. Influence of heat treatments on
mechanical properties was studied,
especially different heat treatment times
and temperatures. The hardness of the cold
sprayed coatings was higher than that
thermally sprayed coatings and bulk
materials. During heat treatment, the
hardness of the cold sprayed coatings
decreased and the ductility increased.
Corrosion resistance of cold sprayed
coatings was also studied. The corrosion
resistance was tested with salt spray (fog)
testing and open cell potential
measurements. The corrosion tests showed
some through-porosity but some parts of the
cold sprayed coatings appeared to be fully
dense, which showed their potential for
corrosion protection. |
|
P. Vuoristo |
|
ITSC2006 |
T. Kairet |
Comparison Between Coatings from two Different Copper
Powders: Mechanical Properties, Hardness and
Bond Strength |
|
|
G. Di Stefano |
Cold sprayed coppercoatings have been widely
studied but the effect of substrate
properties and spraying conditions on the
bond strength still needs further
investigations. Using nanoindentation, it is
possible to compare the effect of spray
parameters on the change in hardness of the
coating due to the difference in size
distribution of the powder. Deposition of 2
copper powders on aluminium and Ta6V
substrates has been done at different
stagnation temperatures and pressures using
nitrogen as process gas. Hardness profiles
show how the speed of the particles induces
shot peening effects on the surface. The
interaction between the hot gas jet and the
surface may modify the hardness profiles.
The effect on the substrate hardness has
also been invesitgated. |
|
M. Degrez |
|
F. Campana |
|
J.P. Janssen |
|
ITSC2006 |
W. Kroemmer |
Cold Spraying - Potential and New Application Ideas |
|
|
P. Heinrich |
Spurred on by the initial success of cold
spray applications, a wide range of
industrial sectors have since shown a
tremendous interest in the youngest of the
thermal spray processes. The forerunner,
oxide-free copper coatings, paved the way
for a variety of materials to be
successfully sprayed at the Linde Technology
Centre in Munich. At the same time, the
hardware for cold spraying also underwent
rapid development. This now means that new
materials can be processed with the highest
efficiency and quality possible, using
lower-cost nitrogen rather than helium which
is decidedly more expensive. |
|
ITSC2006 |
R.E. Blose |
Depositing Titanium Alloy Additive Features to Forgings
and Extrusions Using the Cold Spray Process |
|
|
B.H. Walker |
Development of new low-cost methods for
spray forming Titanium alloys is critical
for many industries. Direct fabrication
technologies would have an impact on many
industries because of the potential for
quick manufacture of parts or additive
features with minimal waste. For example, in
the aerospace industry the buy to fly ratios
can vary from 1.5:1 for turbine blades to
over 22:1 for structural members. The buy to
fly ratio is the mass of material that is
require to machine a part compared to the
mass of material in the finished part. For
compressor and ring sections, the ratio is
approximately 12:1. For this family of
parts, an analysis by Pratt & Whitney [1]
indicated that the buy to fly ratio could be
reduced by 41% to 7:1 if cold spray could be
implemented to deposit isogrids, structural
ribbing, bosses, and flanges reducing the
material, machining, and post processing
required for the final part. This paper
summarizes the results of experiments
conducted in Phase I of a National Science
Foundation grant to spray form Titanium
alloy using the cold spray process. This
paper further describes the studies
performed to date in Phase II and the
techniques used to decrease the porosity of
the as-sprayed coating from 18% to between
2% and 5% and the post processing methods
employed to further consolidate the coating
and restore the as-sprayed material to near
wrought properties |
|
R.M. Walker |
|
S.H. Froes |
|
ITSC2006 |
B. Boro Djordjevic |
SIMAT™ Application for Aerospace Corrosion Protection and
Structural Repair |
|
|
R.Gr. Maev |
Supersonically Induced Mechanical Alloy
Technology (SIMAT™) also known as
gas-dynamic spraying is under development
for corrosion protection and material repair
for aluminum airframe structures. This
technology enables material powder
consolidation that is not possible using
other spray technologies. Similar to cold
spray but based on compact spray head with
nozzle powder feed, SIMAT™ is a low
temperature process and does not create the
high-temperature environment that affects
both the substrate (especially thermally
non-stable substrates) and the deposited
coating. The emerging SIMAT™ technology, now
in development, has the potential for
coating, repairing, joining and rapid
prototyping powder based materials. The
SIMAT™ method adds new flexibility to powder
material deposition producing thin to very
thick deposits of various metals and
metal-ceramic mixtures based on a cold spray
particle kinetic approach inducing impact
fusion. Solid particles in the size range of
10 to 100 microns are accelerated into a
supersonic stream (ranging from 300 to 1200
m/s) using compressed air. These high
velocity cold particles are projected on to
a work piece. There is no heat discharge in
the spray device itself, thus the powder
material retains original characteristics.
This spraying technique can generate a wide
range of deposited layers with thickness
ranging from tens of microns up to as much
as centimeters. The process extends beyond
the concept of "coatings" and includes the
capability for in-situ material build-up and
consolidation to three-dimensional
structures and joining of the components.
The deposition and consolidation can be
performed from a range of hybrid powders
consisting of metals, alloys, ceramics and
glasses. Sample tests demonstrate examples
of the process on typical aircraft
components for new or restored corrosion
protection and demonstrate damage repair for
potential service life extension of the
aircraft structure. |
|
ITSC2006 |
M. Karimi |
Numerical Simulation of the Cold Gas Dynamic Spray Process |
|
|
A. Fartaj |
A computational fluid dynamic (CFD) model of
the cold gas dynamic spray process is
presented. The gas dynamic flow field and
particle trajectories within an oval shaped
supersonic nozzle as well as in the
immediate surroundings of the nozzle exit,
before and after the impact with the target
plane, are simulated. Predicted nozzle wall
pressure values compare well with
experiment. In addition, predicted particle
velocity results at the nozzle exit are in
qualitative agreement with those obtained
using a side-scatter laser Doppler
anemometer (LDA.) Details of the pattern of
particle release into the surroundings are
visualized in a convenient manner. |
|
G.W. Rankin |
|
D. Vanderzwet |
|
J. Villafuerte |
|
W. Birtch |
|
ITSC2006 |
H.J. Kim |
Assessment of Metal/Diamond Composite Coatings by Cold
Spray Deposition |
|
|
D.H. Jung |
Thick metal/diamond composite coatings on Al
substrate were deposited by cold spray
process with in-situ powder preheating.
Microstructural characterization of the
as-sprayed coatings with different diamond
size, strength and with/without Ti clad
coating was carried out by OM and SEM.
Assessment of basic properties such as
tensile bond strength, porosity, and
hardness of the coatings and the deposition
efficiency was also carried out. Particular
attention on the coatings was on the diamond
fracture phenomenon during the cold spray
deposition and the interface bonding between
diamond and metal matrix. The potentials and
the problems of metal/diamond composite
coatings by cold spray are discussed. |
|
J.H. Jang |
|
C.H. Lee |
|
ITSC2006 |
A.N. Papyrin |
Effect of the Coating Erosion on the Cold Spray Process |
|
|
V.F. Kosarev |
In the Cold Spray process, the sprayed
particles are in solid state, and unlike
thermal spray, the effect of the coating
erosion by reflected particles can play a
more significant role. This paper is an
attempt of modeling the process of the Cold
Spray coating formation taking into account
the influence of the erosion process. The
objective was to study the kinetics of the
coating formation. Using an analytical
approach, equations of the coating formation
process are obtained. The approach is based
on a comparison of the effect of particle
adhesion to the coating combined with the
effect of coating erosion. Adhesion and
erosion are taken into account by
introducing some probability values of these
processes. Introduction Heterogeneous flows,
in particular, gas jets containing small
condensed particles are very frequent in
nature and industry. Theoretical models have
been developed, which can predict some
individual aspects of the interaction of
heterogeneous flows with substrates of
various shapes [1-2]. Numerous publications
deal with erosion and heat transfer in
heterogeneous flows around various bodies
[3]. It was also shown that erosion failure
can be converted to the opposite process:
adhesion of particles to the body surface
[4]. The shock impact of fine solid
particles on the substrate includes many
physical and chemical phenomena associated
both with erosion failure and with
origination of new structures in the form of
coatings. Some of them are: elasto-plastic
deformation, destruction of oxide films and
formation of an activated surface, wave
phenomena, formation of structural defects
in the form of dislocations and twins with
subsequent formation of micro-cracks,
fragmentation of particles with a possible
destruction and rebound of certain fragments
of particles. In particular, the range of
erosion failure is rather wide and covers
impact velocities from several meters per
second (dusty winds) to dozens of kilometers
per second, particle materials from liquid
to solid ones, particle sizes from unit
macro-bodies to microns, etc. To describe
the wide spectrum of these phenomena taking
place under interaction between
heterogeneous flows and substrates, in
particular under the Cold Spray process,
more adequate physical models should be
developed. In the Cold Spray process, the
sprayed particles are in solid state, and
unlike thermal spray, the effect of the
coating erosion by reflected particles can
play a more significant role. This paper is
an attempt to consider some aspects of
modeling of the process of the Cold Spray
coating formation taking into account the
influence of the erosion process.
Nomenclature a – empirical coefficient a –
constant solution for areas s kk b –
empirical coefficient d – diameter of the
particle |
|
S.V. Klinkov |
|
ITSC2006 |
B. Sun |
Effect of Spraying Parameters on Stainless Steel Particle
Velocity and Deposition Efficiency in Cold
Spraying |
|
|
R.Z. Huang |
In the cold spraying process, particle
velocity is commonly regarded as the key
factor which influences the deposition
efficiency and properties of the coating. In
the present paper the in-flight particles
velocity were measured using a DPV-2000
system. The influences of He and N2 gas
pressure and temperature and particle
morphology on the particle velocity and
deposition efficiency of the coating using
stainless steel 316L powders were studied.
The microstructure of the coating was
examined using optical microscopy. The
critical velocity of stainless steel 316L
powders was estimated according to the
particle velocity distribution and
deposition efficiency of the coating. The
experiment results suggested that the gas
pressure has a more significant influence on
the particle velocity and deposition
efficiency of the coating than that of the
gas temperature. The particle morphology
also has significant influence on the
particle velocity. The critical velocity of
stainless steel 316L powders was in the
range of 630 and 680 m/s and it decreased
slightly with the gas temperature. |
|
N. Ohno |
|
H. Fukanuma |
|
ITSC2006 |
S. Verajankorva |
Influence of Powder Type and Properties on Ceramic Layer
Deposition by Cold Spraying |
|
|
J. Lagerbom |
Ceramic deposition produced by cold spraying
was studied for functional surface
applications. Several oxide materials and
metal matrix composite (MMC) powders were
used to model the behavior of ceramic powder
deposition on soft metallic substrate
materials. The manufacturing method, density
and size of ceramic powders and matrix
material of MMC were found to affect the
deposition on soft metal surfaces. The
powder density influences the deposition
greatly and it is also an important factor
in finding an ideal powder particle size.
Fusing and crushing the powder can be a good
manufacturing method if the fusion does not
cause phase transformations in the powder.
In that case, spray drying with sintering
can give better results. Spraying
parameters, such as the process gas
parameters and the effect of multiple sweeps
of the torch were also studied to optimize
the amount of deposition. Cold spraying was
found to be a promising manufacturing method
for functional surfaces. |
|
P. Vuoristo |
|
ITSC2006 |
R. Gr. Maev |
Low Pressure Gas Dynamic Spray: Shear Localization During
Particle Shock Consolidation |
|
|
V. Leshchynsky |
Gas Dynamic Spray (GDS) is a high rate,
direct material-deposition process that
utilizes the kinetic energy of particles
sprayed at supersonic velocities to cause
bonding through the particle plastic
deformation on impact. GDS seems to be
similar to the powder shock consolidation
process, which is governed by dynamic
regimes of granular material deformation
under impulse loading. These regimes are
characterized by adiabatic shear band (ASB)
formation. This paper describes the
preliminary analysis of ASB formation during
GDS on the basis of a combination of the
Johnson-Cook and shock wave consolidation
models. The dependence of the ASB width on
different parameters, including initial
powder porosity, average impact stress,
shear strain, initial temperature, and
contact time was determined. The ASB width
was found to vary in the range of 0.5–15 µm,
which reveals the great localization of
particle deformation in the GDS process. |
|
ITSC2006 |
P. Richer |
Properties of Cold Spray Nickel Based Coatings |
|
|
B. Jodoin |
Nickel based alloys used in coating
applications have been the focus of many
studies, particularly in the aerospace
industry. Their inherent corrosion and
oxidation resistant properties have made
them especially attractive for use as the
metallic bond coat found in thermal barrier
coating systems. Cold Spray is an emerging
coating technology in which fine powder
particles are accelerated in a supersonic
flow and then deposited onto a substrate by
means of plastic deformation. In this study,
conventional CoNiCrAlY coatings and
nanocrystalline nickel coatings are produced
using the Cold Spray deposition technique.
The coating quality is evaluated using
scanning electron microscopy as well as
porosity and microhardness measurements. |
|
E. Sansoucy |
|
L. Ajdelsztajn |
|
G.E. Kim |
|
ITSC2006 |
J.H. Lee |
Effect of Particle Temperature on the Critical Velocity
for Particle Deposition by Kinetic Spraying |
|
|
J.S. Kim |
This study evaluated the effects of particle
temperature on deposition efficiency and
critical velocity in kinetic spraying. A
wide range of pressures and preheat
temperatures of the process gas were used in
these experiments to vary both particle
velocity and temperature, and a bronze
(Cu-Sn alloy) powder was deposited onto
aluminum and bronze substrates. The
deposition efficiency of the coatings was
measured, and the critical velocity was
estimated. The experimental results showed
that the critical velocities of the bronze
feedstock deposited onto either an aluminum
or bronze substrate were different and that
the critical velocity was strongly dependent
on the particle temperature, which when
increased, caused the critical velocity to
decrease. Increasing the gas pressure caused
an increase in particle velocity, while
increases in the gas temperature not only
affected the particle velocity but also the
particle temperature. In our experiments,
the critical velocity decreased by 50 m/s
when the process gas temperature increased
by 100 oC. |
|
S.M. Shin |
|
C.H. Lee |
|
H.J. Kim |
|
ITSC2006 |
J.W. Wu |
Critical and Maximum Velocities in Kinetic Spraying |
|
|
H.Y. Fang |
Critical velocity has been accepted as a
characteristic property of kinetic spraying
(or cold gas dynamic spraying), which works
by accelerating small solid particles to
supersonic velocities and then impacting
them onto a substrate. However, there is a
lack of information about the impact of
individual particles and their deposition
behavior over a large range of impact
velocities. To probe into the impact
behavior of the particles and to elucidate
the deposition mechanism, individual
particle impaction tests have been carried
out. A rebound phenomenon was found to occur
at a high impact velocities, in which a
large fraction of the particles rebounded.
Based on experimental results, a model of a
plastic particle impacting onto an
un-deformed substrate was developed. The
adhesion and rebound energies were
calculated to estimate the
particle/substrate interactions. A maximum
impact velocity was found for particle
deposition onto the substrate. The particle
deposition behavior was controlled by the
adhesion and rebound energies. |
|
C.H. Lee |
|
S.H. Yoon |
|
H.J. Kim |
|
ITSC2006 |
S.Q. Fan |
Characterization of Microstructure of TiO2 Coating
Deposited by Vacuum Cold Spraying |
|
|
G.J. Yang |
The control of microstructure of TiO2
coating through preparation methods
influences significantly the performance of
the coating. In this study, vacuum cold
spray process as a new coating technology is
employed to deposit nanocrystalline TiO2
coatings on glass and stainless steel
substrates. TiO2 deposits were formed using
two types of nanocrystalline TiO2 powders
having mean particle diameters of 200 nm and
25 nm. The microstructure of the coating was
characterized by scanning electron
microscopy, x-ray diffraction analysis. The
results demonstrate that a thick
nanocrystalline TiO2 coating can be
deposited by vacuum cold spray process. The
coating was stacked of particles in
agglomerate of several hundred nanometers.
The coating presents a mesoporous
microstructure which would be effective for
applications in photocatalytic degradation,
dye-sensitized solar cell and so on.was
stacked of particles in agglomerate of
several hundred nanometers. The coating
presents a mesoporous microstructure which
would be effective for applications in
photocatalytic degradation, dye-sensitized
solar cell and so on. |
|
G.J. Liu |
|
C.X. Li |
|
C.J. Li |
|
L.Z. Zhang |
|
ITSC2006 |
W.Y. Li |
Measurement and Numerical Simulation of Particle Velocity
in Cold Spraying |
|
|
C.J. Li |
The velocity of cold spray particles was
measured by a diagnostic system for thermal
spray particles based on thermal radiation.
A laser beam was employed to illuminate the
cold sprayed particles in cold spraying for
obtaining a sufficient radiant energy
intensity for detection. The measurement was
carried out for Cu particles of different
mean particle sizes. The particle velocity
was also estimated using the previously
developed two-dimensional axisymmetric
model. It was found that the measured
results agreed well with the calculated
ones. The proposed measurement method in
this paper is reliable. On the other hand,
it is confirmed that the particle
acceleration behavior in cold spraying can
be accurately predicted through the
simulation method developed previously. The
optimization of cold spray process can be
conducted following the simulation method. |
|
H.T. Wang |
|
C.X. Li |
|
ITSC2006 |
W.Y. Li |
Optimal Design of a Convergent-Barrel Cold Spray Nozzle by
Numerical Method |
|
|
H.L. Liao |
A convergent-barrel (CB) cold spray nozzle
was designed through numerical simulation.
It was found that the main factors
influencing significantly the particle
velocity and temperature include the length
and diameter of the barrel section, the
nature of the accelerating gas and the
operating gas pressure and temperature, and
the particle size. Particles can achieve a
relatively low velocity but a high
temperature under the same gas pressure
using a CB nozzle compared to a
convergent-divergent (CD) nozzle. The
experiment results with Cu powder using the
designed CB nozzle confirmed that the
deposition can be realized under a lower gas
pressure with a CB nozzle. |
|
G. Zhang |
|
C. Coddet |
|
H.T. Wang |
|
C.J. Li |
|
ITSC2006 |
T. Marrocco |
Comparison of the Microstructure of Cold Sprayed and
Thermally Sprayed IN718 Coatings |
|
|
D.G. McCartney |
High-temperature nickel-based superalloys
such as IN718 are widely used in gas turbine
components as they remain stable at
operating temperatures up to ~750°C. There
is now a growing interest in the repair and
refurbishment of such components using spray
deposition techniques. Although many
investigations have been carried out to
study the effect of conventional processing
on the microstructure and mechanical
properties of IN718, much less attention has
been given to the alloy when sprayed to form
a coating. The purpose of the present study
was to investigate and compare IN718
deposits produced by HVOF spraying and cold
gas spray deposition. Optical microscopy,
scanning electron microscopy and X-ray
diffraction were employed to examine the
microstructural evolution of the coatings
and to compare the deposition behaviour of
the two different processes. Particular
attention was paid to porosity, oxide
content and the formation of secondary
intermetallic phases. Coating microhardness
and bond strength were also measured.
Results will be presented and discussed in
the context of the different thermal
histories of the powder particles in the two
processes. |
|
P.H. Shipway |
|
A.J. Sturgeon |
