U.S. patent application number 11/385734 was filed with the patent office on 2006-09-28 for method of depositing an anti-wear coating by thermal spraying.
This patent application is currently assigned to SNECMA. Invention is credited to Per Bengtsson, Laurent Paul Dudon, Gerard Michel Roland Gueldry, Michel Hacala.
Application Number | 20060216429 11/385734 |
Document ID | / |
Family ID | 34954892 |
Filed Date | 2006-09-28 |
United States Patent
Application |
20060216429 |
Kind Code |
A1 |
Bengtsson; Per ; et
al. |
September 28, 2006 |
Method of depositing an anti-wear coating by thermal spraying
Abstract
A method of depositing an anti-wear coating on a mechanical part
by thermal spraying of the AC-HVAF type, said coating being made of
a copper-based alloy containing 30% to 42% by weight of nickel and
4% to 6% by weight of indium.
Inventors: |
Bengtsson; Per; (Avon,
FR) ; Dudon; Laurent Paul; (Viry-Chatillon, FR)
; Gueldry; Gerard Michel Roland; (Evry, FR) ;
Hacala; Michel; (St. Charels-sur-Richelieu, CA) |
Correspondence
Address: |
C. IRVIN MCCLELLAND;OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
SNECMA
Paris
FR
PLASMATEC
MONTREAL
CA
|
Family ID: |
34954892 |
Appl. No.: |
11/385734 |
Filed: |
March 22, 2006 |
Current U.S.
Class: |
427/446 |
Current CPC
Class: |
F05D 2230/31 20130101;
F05D 2300/1723 20130101; C23C 4/12 20130101; C23C 4/06 20130101;
F01D 5/288 20130101 |
Class at
Publication: |
427/446 |
International
Class: |
C23C 4/00 20060101
C23C004/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 23, 2005 |
FR |
05 002865 |
Claims
1. A method of depositing an alloy of copper, nickel, and indium by
thermal spraying to constitute an anti-wear coating on a mechanical
part, wherein said coating is deposited by thermal spraying of the
AC-HVAF type.
2. A method according to claim 1, wherein said coating is a
copper-based alloy containing 30% to 42% by weight of nickel and 2%
to 8% by weight of indium.
3. A method according to claim 2, wherein said coating is a
copper-based alloy containing 34% to 38% by weight of nickel and 4%
to 6% by weight of indium.
4. A method according to claim 3, wherein said coating is a
copper-based alloy containing 36% by weight of nickel and 5% by
weight of indium.
5. A method according to claim 1, wherein said mechanical part for
coating is a part made of titanium or titanium alloy.
6. A method according to claim 1, wherein said coating is deposited
on at least one part taken from two parts of a gas turbine that are
liable to come into contact with each other.
7. A method according to claim 1, wherein said coating is deposited
on a fan or compressor blade root of a turbomachine, and/or the fan
or compressor disk in which said blade root is engaged.
Description
[0001] The invention relates to a method of depositing an anti-wear
coating on a mechanical part by thermal spraying, and more
particularly it relates to a gas turbine part made of titanium or
titanium alloy such as a fan blade or a compressor blade of a
turbomachine.
BACKGROUND OF THE INVENTION
[0002] Fan or compressor blades constitute good examples of parts
that are subjected to wear while a turbine is in operation. Such
blades are held by their roots in slots of appropriate shape that
are formed in the peripheries of rotary disks, referred to below as
compressor disks or fan disks.
[0003] While a turbojet is in operation, the blade roots move in
said slots under the effects of centrifugal force and of vibration.
The roots of blades are shaped in a manner that matches the shapes
of the slots so as to make such relative displacements possible.
The surfaces of blade roots that come to bear against the edges of
said slots under the effect of centrifugal force are subjected to
significant compression stresses (which are generally cyclical).
These stresses in combination with vibratory movement damage and
wear said surfaces. The wear that is observed is found to be even
greater when the blade roots and the fan or compressor disks are
made of titanium or titanium alloy. This is because the coefficient
of friction of titanium on titanium is rather high.
[0004] To protect blade roots, it is known to make use of anti-wear
coatings that are constituted by copper nickel alloys (CuNi),
copper aluminum alloys (CuAl), or indeed copper nickel indium
alloys (CuNiIn). It is generally preferred to use a copper nickel
indium type alloy (CuNiIn) since it presents better mechanical
characteristics at high temperatures.
[0005] In order to deposit these alloys on blade roots, it is
common practice to use a thermal spraying technique known as plasma
spraying. That technique can be implemented using a plasma gun such
as that described in U.S. Pat. No. 3,145,287. Plasma spraying
consists in bringing alloy powder to a plasma torch that is
producing a jet of gas at very high temperature: greater than
2000.degree. C. The speed at which the particles are sprayed lies
in the range 100 meters per second (m/s) to 400 m/s.
[0006] The microstructure of the coating deposited by plasma
spraying nevertheless presents very high porosity and oxidation,
thereby affecting the mechanical properties of the coating. In
addition, the coating adheres poorly on titanium or titanium alloy.
Thus, in practice, it is found that the coating flakes away quickly
and is poor at withstanding the stresses to which it is subjected
while the turbine is in operation.
[0007] A second type of thermal spraying is also used for
depositing anti-wear coatings: this is known as high velocity oxy
fuel (HVOF) spraying which consists in taking advantage of
combustion between oxygen and a fuel gas such as propane,
propylene, hydrogen, or propadiene methyl acetylene, in order to
heat and propel molten grains of alloy powder at very high speed.
The temperatures reached with that method lie in the range
1500.degree. C. to 2000.degree. C. and the spray speeds lie in the
range 300 m/s to 700 m/s. An example of depositing a nickel-based
alloy using HVOF spraying is described in U.S. Pat. No.
5,518,683.
[0008] Although the lifetime of a deposit obtained with an HVOF
method is better than that of a deposit obtained by plasma
spraying, it is nevertheless found that the coating flakes quickly
under ordinary conditions of turbomachine operation.
OBJECTS AND SUMMARY OF THE INVENTION
[0009] An object of the invention is to propose a novel method of
deposition that makes it possible to deposit anti-wear coatings
that are better at withstanding the stresses to which they are
subjected than are the coatings obtained by existing methods.
[0010] To achieve this object, the invention provides a method of
depositing an alloy of copper, nickel, and indium by thermal
spraying to constitute an anti-wear coating on a mechanical part,
wherein said coating is deposited by thermal spraying of the
activated combustion high velocity air fuel (AC-HVAF) type.
[0011] Thermal spraying of the AC-HVAF type is a known technique
that differs from the above-mentioned HVOF spraying mainly by using
a mixture of air and a fuel gas such as propane (instead of a
mixture of oxygen and gas) that is burnt in order to heat and
propel an alloy powder at very high speed. With AC-HVAF spraying,
the molten alloy particles are sprayed at a speed lying
substantially in the range 600 m/s to 800 m/s, and the temperatures
reached lie in the range 800.degree. C. to 1500.degree. C.
[0012] The temperatures reached during spraying of the AC-HVAF type
are lower than those reached during spraying of the HVOF or plasma
type. This serves to limit oxidation of the sprayed particles.
[0013] In addition, the spray speeds that can be obtained with the
AC-HVAF method are higher than the speeds obtained by plasma or
HVOF spraying. Thus, the lapse of time between the moment when the
particles are sprayed and the moment when they reach the part to be
coated, during which time lapse the particles are particularly
sensitive to oxidizing, is itself shortened. This also contributes
to reducing the extent to which the coating is oxidized.
[0014] In addition, the high kinetic energy of the particles
sprayed onto the part for coating makes it possible firstly to
achieve better bonding of the particles on the part, and secondly
to obtain a coating that is more compact, presenting porosity that
is less than that obtained with the methods that have been used in
the past. In particular, the structure of the resulting coating is
unitary and not lamellar.
[0015] Decreasing the porosity and the quantity of oxide in the
coating leads specifically to a reduction in the number of
incipient cracks in the microstructure of the coating. This leads
to greater ability to withstand stresses and more particularly the
compression stresses to which the coating is subjected. Since the
coating is also more compact and adheres better to the part on
which it is coated, it is found in practice that problems of
flaking occur less quickly during operation of the gas turbine, and
that the lifetime of the coating of the invention is considerably
better than that of known coatings.
[0016] Finally, by its very nature, AC-HVAF thermal spraying is
less expensive than plasma spraying.
[0017] Advantageously, said coating is constituted by a
copper-based alloy containing 30% to 42% by weight of nickel and 2%
to 8% by weight of indium.
[0018] More advantageously, it is possible for said coating to
comprise a copper-based alloy comprising 34% to 38% by weight of
nickel and 4% to 6% by weight of indium.
[0019] As already emphasized, CuNiIn coatings are advantageous
since they are mechanically very strong at high temperatures.
[0020] While undertaking research to improve the lifetime of
anti-wear coatings of this type, the Applicant company has found
that the melting temperatures of CuNiIn alloys are much lower than
the temperatures reached during plasma spraying, and lower than
those reached during a HVOF type spraying. In contrast, the
temperatures reached during AC-HVAF spraying turn out to be of the
same order as the melting temperatures of said CuNiIn alloy. It has
thus been found that by using the AC-HVAF method, it is possible to
melt a CuNiIn alloy while avoiding any useless oxidation associated
with temperatures that are too high. The AC-HVAF method thus turns
out to be particularly well suited to depositing CuNiIn
coatings.
[0021] Advantageously, once the CuNiIn anti-wear coating has been
deposited, a lubricating varnish layer is deposited thereon, e.g.
comprising molybdenum disulfide (MoS.sub.2) and an organic resin.
CuNiIn coatings present high roughness and it is advisable to cover
them in a layer of varnish having a low coefficient of friction in
order to encourage sliding and limit wear. The combined coating of
CuNiIn and a layer of lubricant gives results that are entirely
satisfactory in terms of protecting the part and in terms of the
lifetime of the coating.
[0022] Although the only embodiment of a part described in the
present description is a titanium blade for a turbomachine
compressor or fan, it is clear that the method of the invention can
be used for coating any type of part, regardless of whether it is
made of titanium or a titanium alloy. For example, the method can
be used for coating at least one part taken from any two gas
turbine parts of any kind that are liable to come into contact with
each other.
BRIEF DESCRIPTION OF THE DRAWING
[0023] The invention and its advantages can be better understood on
reading the following detailed description of embodiments of the
invention that are given as non-limiting examples. The description
refers to the accompanying figures, in which:
[0024] FIG. 1 is a comparative plot;
[0025] FIG. 2 is a micrograph of a CuNiIn coating deposited by
AC-HVAF spraying in accordance with the method of the
invention;
[0026] FIG. 3 is a micrograph of a CuNiIn coating deposited by
plasma spraying;
[0027] FIG. 4 is a diagram of a device enabling the stresses
exerted on a fan blade root in operation to be simulated; and
[0028] FIG. 5 is a graph showing a cycle in the variation of the
traction force exerted on a fan blade root in operation, as a
function of time.
MORE DETAILED DESCRIPTION
[0029] The plot of FIG. 1 has spray speed in m/s plotted along the
abscissa and spray temperature in .degree. C. plotted up the
ordinate, as obtained when using various thermal spraying methods.
In this plot, there can be seen outlines for temperature and spray
speed ranges for plasma, HVAF, and AC-HVAF spraying. Furthermore,
the range of temperatures over which a copper-based alloy such as
the CuNiIn alloy melts is also shown.
[0030] In this diagram, and as described above, it can be seen that
the temperatures reached in AC-HVAF spraying are adapted to the
melting range of the CuNiIn alloy used in the invention, thus
making it possible to melt these alloys without useless overheating
that would encourage oxidation. Furthermore, it can also be seen
that higher spraying speeds can be obtained by using AC-HVAF
spraying.
[0031] An implementation of the method of the invention is
described below by way of example, in which a CuNiIn alloy was
deposited on a part made of a titanium alloy of the TA6V type.
Operating conditions were as follows:
Device Used:
[0032] An SB-500 model AC-HVAF torch sold by the supplier
Uniquecoat Technologies.
Powder Used:
[0033] Composition: CuNiIn alloy comprising 36% by weight Ni, 5% by
weight In, with the balance being Cu;
[0034] Particle size: 11 micrometers (.mu.m) to 45 .mu.m;
[0035] Torch feed rate: 8 kilograms per hour (kg/h);
[0036] Carrier gas: nitrogen.
Operating Parameters of the Torch:
[0037] Gas: propane;
[0038] Air pressure: 85 pounds per square inch (psi);
[0039] Pressure 1, propane; 74 psi;
[0040] Pressure 2 (0) of propane: 38 psi;
[0041] Pressure of carrier gas: 41 psi;
[0042] Distance: 150 millimeters (mm) to 165 mm;
[0043] Coating deposition rate: 45 .mu.m per pass.
Information Concerning the Coated Part:
[0044] Preparation: sandblasting with aluminum oxide particles
having a mean size of 300 .mu.m;
[0045] Initial temperature: 29.degree. C.;
[0046] Temperature variation: 50.degree. C. to 95.degree. C.
[0047] The thickness of the deposited coating was 165 .mu.m, but
greater thicknesses could have been obtained without any particular
difficulty. The measured porosity of the coating was less than
1%.
[0048] The micrograph of FIG. 2 was taken of the CuNiIn coating
deposited using AC-HVAF in accordance with the invention, while the
micrograph of FIG. 3 was taken using a CuNiIn coating obtained by
plasma spraying.
[0049] The oxides and the pores appear in the form of black spots
in the layer of coating 2 deposited on the substrate 1.
[0050] It can clearly be seen that the presence of oxides and pores
in the coating of FIG. 2 is less than in the coating of FIG. 3.
Furthermore, it can be seen that the coating of FIG. 2 presents a
microstructure that is compact and unitary, whereas that of the
coating of FIG. 3 is lamellar. Consequently, the coating deposited
with the method of the invention is less subject to becoming
delaminated (and thus to flaking) than is the coating obtained by
plasma spraying. To sum up, the microstructure of the coating in
FIG. 2 is mechanically stronger.
[0051] In order to simulate the mechanical stresses to which a fan
blade is subjected in operation, a device was used similar to that
shown in FIG. 4 in which a mechanical part 10 representing the
blade was mounted via its root 14 in a slot 15 defined between two
uprights 16a and 16b, and it was held in position between two jaws
18. The assembly made in this way is analogous to a dovetail
assembly. In this case the uprights 16a and 16b represented the fan
disk. The root 14 of the part 10 had two surfaces 14a and 14b that
were in contact with the uprights 16a and 16b. A cyclical traction
force F was exerted on the part 10. The way the force F varied as a
function of time is shown in FIG. 5.
[0052] The behavior of a CuNiIn coating deposited using AC-HVAF
spraying in accordance with the invention was tested for 30,000
traction cycles. After 30,000 cycles, no flaking and no wear were
observed. With a CuNiIn coating deposited by plasma spraying,
flaking appeared in the range 15,000 cycles to 19,000 cycles.
[0053] This test demonstrates the significant improvement in terms
of coating lifetime that the invention makes it possible to
obtain.
* * * * *