Composite Compressor Impeller with An Erosion Resistant Coating and
Methods of Manufacturing
BACKGROUND
TECHNICAL FIELD
Embodiments of the subject matter disclosed herein generally relate to
methods of manufacturing and impellers manufactured to have an erosion
resistant coating.
DISCUSSION OF THE BACKGROUND
Compressors are a particular type of turbo-machine that increases the
pressure of a compressible fluid (e.g., gas) by using mechanical energy.
Various types of compressors are used in processing plants in the oil and gas
industry. Among these compressors, there is the so-called centrifugal
compressor in which energy is supplied to the gas particles by centrifugal
acceleration. The centrifugal acceleration may be achieved by the rotation of
a rotating member. The rotating member includes one or more impellers.
Depending on its particular geometry and its functional principle, an
impeller may include a well-defined fluid pathway. For example, a centrifugal
impeller 1 is shown in Figure 1 and has blades 3, connected to a hub 2, and
covered by a shroud 4, which may be made of composite material. The
impeller 1 has a substantially three-dimensional profile around a rotational
axis X3D. A fluid flow passes from an axial inlet orifice 5 towards a
substantially radial outlet orifice 7 . A pathway between the inlet orifice 5 and
the outlet orifice 7 is a flow path cavity.
Traditionally impellers were made of metal. Recently impellers made
partially or fully from composite materials have an increasing share in the
impeller market. The impellers made partially or fully from composite
materials have better corrosion resistance in certain environments, such as,
the ones occurring in oil and gas drilling.
One problem with the composite impeller is that the composite material
has a lower erosion resistance than metals, that is, the composite material
wears away due to impact with solid particles or liquid droplets in the flow.
This low erosion resistance, in particular around flow path cavities, leads to a
relative fast destruction of the impeller and, thus, to down time for replacing it.
Epoxy paints have been applied on composite impeller in an attempt to
enhance erosion resistance. However, these paints have low adhesion and
do not provide enough protection, for example, when impellers are used in oil
and gas industry where a mainly fluid flow includes solid particles or liquid
droplets.
Accordingly, it would be desirable to provide systems and methods that
avoid the afore-described problems and drawbacks.
SUMMARY
According to one exemplary embodiment, a method of manufacturing a
composite impeller with flow path cavities having an erosion resistant coating
is provided. The method includes (i) providing molds having shapes
corresponding to a negative geometry of the flow path cavities, (ii) covering
the molds with an erosion resistant coating, (iii) shaping a composite material
around the molds covered with the erosion resistant coating, according to a
predetermined impeller geometry, (iv) curing the composite material, and (v)
removing the molds to leave the erosion resistant coating on the flow path
cavities of the composite impeller.
According to another embodiment, an impeller has blades, a shroud in
contact with the blades and having flow path cavities therethrough, and an
erosion resistant coating on the flow path cavities. The erosion resistant
coating is made by (i) providing water-soluble molds having shapes
corresponding to a negative geometry of flow path cavities, (ii) coating the
molds with a sealant, (iii) applying a conductive paint over the sealant, (iv)
plating an erosion resistant layer over the conductive paint, (v) shaping a
composite material around the molds covered with the sealant, the conductive
paint and the erosion resistant coating, according to a predetermined
geometry, (vi) curing the composite material, and (vii) dissolving the molds in
a water-based solution while leaving at least the erosion resistant coating on
the flow path cavities of the impeller.
According to another exemplary embodiment, an impeller has blades, a
shroud in contact with the blades and having flow path cavities therethrough
and an erosion resistant coating on the flow path cavities. The erosion
resistant coating is made by (i) providing metallic molds having shapes
corresponding to a negative geometry of flow path cavities, (ii) covering the
molds with an erosion resistant layer using thermal spraying, (iii) shaping a
composite material around the molds covered with the erosion resistant
coating, according to a predetermined geometry, (iv) curing the composite
material, and (v) dissolving the molds in an acid solution or in a basic solution,
while leaving at least the erosion resistant coating on the flow path cavities of
the impeller.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute
a part of the specification, illustrate one or more embodiments and, together
with the description, explain these embodiments. In the drawings:
Figure 1 is an illustration of an impeller with a well defined flowpath
therethrough;
Figure 2 is an illustration of flow path cavity molds useable in various
exemplary embodiments;
Figure 3 is a flow chart of a method of manufacturing composite
impellers with flow path cavities having erosion resistant coating, according to
an exemplary embodiment;
Figure 4 is a schematic illustration of shaping of composite around
molds covered with an erosion resistant coating, which is incorporated in
various exemplary embodiments;
Figure 5 is a schematic diagram of material layers according to various
embodiments, prior to dissolving a mold material;
Figure 6 is a flow chart of a method of manufacturing composite
impellers with flow path cavities having erosion resistant coating, according to
another exemplary embodiment; and
Figure 7 is a flow chart of a method of manufacturing composite
impellers with flow path cavities having erosion resistant coating, according to
another exemplary embodiment.
DETAILED DESCRIPTION
The following description of the exemplary embodiments refers to the
accompanying drawings. The same reference numbers in different drawings
identify the same or similar elements. The following detailed description does
not limit the invention. Instead, the scope of the invention is defined by the
appended claims. The following embodiments are discussed, for simplicity, with
regard to the terminology and structure of composite impellers useable in the oil
and gas industry. However, the embodiments to be discussed next are not
limited to these systems, but may be applied to other systems that use
composite impellers in a fluid flow that includes solid particles or liquid droplets.
Reference throughout the specification to "one embodiment" or "an
embodiment" means that a particular feature, structure, or characteristic
described in connection with an embodiment is included in at least one
embodiment of the subject matter disclosed. Thus, the appearance of the
phrases "in one embodiment" or "in an embodiment" in various places
throughout the specification is not necessarily referring to the same
embodiment. Further, the particular features, structures or characteristics may
be combined in any suitable manner in one or more embodiments.
Flow path cavities soluble molds are used in manufacturing composite
impellers having flow path cavities. Flow path cavity molds 10 are illustrated
in Figure 2 . Each of the molds 10 has a complex three dimensional shape,
with a geometry which is complementary to the geometry of the flow path
cavity in the manufactured impeller. Being complementary means that a mold
has the shape of a liquid filling the cavity of the impeller, and the geometry of
the mold may be indicated as a negative geometry.
The molds 10 may be made of a water-soluble material or of a metal
that can be dissolved using strong acid or basic solutions. As an example of
water-soluble material may be a water-soluble epoxy resin or a material such
as the material currently marketed under the name AQUAPOUR™
(manufactured by AeroConsultants, Switzerland). Metals that can be used to
manufacture the molds are copper and mild steel (i.e., steel with less than
15% C) and other metal alloys.
A flow chart of a method 100 of manufacturing a composite impeller
with flow path cavities having erosion resistant coating according to an
exemplary embodiment is illustrated in Figure 3 . The method 100 includes
providing molds (e.g., 10) having shapes corresponding to a negative
geometry of the flow path cavities at S 110, and covering the molds with an
erosion resistant coating (e.g., at S 120. The method 100 further includes
shaping a composite material around the molds covered with the erosion
resistant coating, according to a predetermined impeller geometry, at S 130,
and curing the composite material, at S140. A way of shaping of the
composite material around the molds covered with the erosion resistant
coating, according to the predetermined impeller geometry is illustrated in
Figure 3 where the molds 10, which have been covered with the erosion
resistant coating 20 and are arranged around a core 30 are surrounded by the
composite material 40. The composite material may include a resin.
Depending on its exact composition a curing temperature may be from room
temperature to a few hundreds of degrees Celsius.
Finally, the method 100 includes dissolving the mold (e.g., 10) to leave
the erosion resistant coating (e.g., 20) on the flow path cavities of the
composite impeller (e.g., 40) having the predetermined impeller geometry at
S 150. Prior to dissolving the molds, at an interface between the mold material
10 and the composite material 40, there is the erosion resistant layer 20 as
illustrated in Figure 5 . Once the mold 10 is dissolved, the composite material
40 and the erosion resistant layer 20 remain together.
The manner in which the erosion resistant layer (e.g., 20) is applied on
the molds (e.g., 10) depends on the mold material. If the mold is made of a
water-soluble material, a plating process may be used. If the mold is made of
metal, a plating process, a thermal spraying process, a physical vapor
deposition (PVD) process, a chemical vapor deposition (CVD) process or a
cold spray process may be used.
The plating process applied on a water-soluble mold includes (i)
coating the mold with a sealant, (ii) applying a conductive paint over the
sealant and (iii) plating the erosion resistant layer over the conductive layer.
The sealant may be a thin layer of epoxy paint applied with a brush. The
conductive layer may be a thin layer of paint including silver (Ag) and may
also be applied with a brush.
The plating of the erosion layer may include plating a Ni-base layer to
provide a basis of growing an erosion resistant structure over it. The plating
of this Ni-based layer may be performed using Woods nickel strike. The
thickness of the Ni-based layer may be less than 1 mil (i.e., 1/1 000 of an
inch).
The bulk of the erosion resistant layer may then be applied using
electroless nickel plating (ENP). Electroless plating utilized a chemical
solution containing metallic ions but no direct current is applied. The
electroless plating provides the advantage that uniform layers can be applied
uniformly on objects having complex geometries.
The erosion resistant layer plated using ENP may include diamonds of
less than 2 maximum size, in a proportion around 35% by volume. After
the composite material is cured, the water-soluble mold is easily removed
using water. The erosion resistance of an impeller having such an erosion
resistant layer is about five times larger than that of an impeller without such a
layer.
The plating process may be applied also on a mold made of metal.
However, on a mold made of metal, the erosion resistant layers may also be
applied using a thermal spraying process. The erosion resistant layers
applied by thermal spraying provide ten times better resistance than the
erosion resistant layers applied by plating.
The erosion resistant layers applied by thermal spraying may be either
metallic or cermets. The preferred erosion resistant thermal spray coatings
are and cermets and they include both a ceramic and a metallic matrix. For
example, the ceramic is WC and the metallic matrix may be a combination of
Co and Cr, Ni or a combination of Ni and Cr. Specifically, for the ceramic WC,
a combination 10Co4Cr has been tested where 10 and 4 represent volume
percentage of the metals. In another example, the ceramic is C 2Co3 and the
metallic matrix is NiCr. The thickness of the erosion resistant layer applied
using thermal spraying may be over 10 mil.
A composite impeller with flow path cavities having an erosion resistant
coating according to another exemplary embodiment can be made using the
method 200 illustrated in Figure 6 . The method 200 includes providing watersoluble
molds having shapes corresponding to a negative geometry of the
flow path cavities at S21 0, coating the molds with a sealant at S220, applying
a conductive paint over the sealant at S230, plating an erosion resistant layer
over the conductive paint at S240, shaping a composite material around the
molds covered with the sealant, the conductive paint and the erosion resistant
coating, according to a predetermined impeller geometry at S250, curing the
composite material at S260 and dissolving the molds in a water-based
solution while leaving at least the erosion resistant coating on the composite
impeller at S270.
A composite impeller with flow path cavities having an erosion resistant
coating according to another exemplary embodiment can be made using the
method 300 illustrated in Figure 6 . The method 300 includes providing
metallic molds having shapes corresponding to a negative geometry of the
flow path cavities at S31 0, covering the molds with an erosion resistant
coating using thermal spraying at S320, shaping a composite material around
the molds covered with the erosion resistant coating, according to a
predetermined impeller geometry at S330, curing the composite material at
S340, and dissolving the molds in an acid solution or in a basic solution, while
leaving the erosion resistant coating on the composite material at S350.
The disclosed exemplary embodiments provide methods of producing
impellers made of composite materials to have flow path cavities covered by
an erosion resistant coating, the erosion resistant coating being initially
applied on molds by plating or thermal spraying. It should be understood that
this description is not intended to limit the invention. The exemplary
embodiments are intended to cover alternatives, modifications and
equivalents, which are included in the spirit and scope of the invention as
defined by the appended claims. Further, in the detailed description of the
exemplary embodiments, numerous specific details are set forth in order to
provide a comprehensive understanding of the claimed invention. However,
one skilled in the art would understand that various embodiments may be
practiced without such specific details.
Although the features and elements of the present exemplary
embodiments are described in the embodiments in particular combinations,
each feature or element can be used alone without the other features and
elements of the embodiments or in various combinations with or without other
features and elements disclosed herein.
This written description uses examples of the subject matter disclosed to
enable any person skilled in the art to practice the same, including making and
using any devices or systems and performing any incorporated methods. The
patentable scope of the subject matter is defined by the claims, and may include
other examples that occur to those skilled in the art. Such other examples are
intended to be within the scope of the claims.
CLAIMS
1. A method of manufacturing a composite impeller with flow path
cavities having an erosion resistant coating, the method comprising:
providing molds having shapes corresponding to a negative geometry
of the flow path cavities;
covering the molds with an erosion resistant coating;
shaping a composite material around the molds covered with the
erosion resistant coating, according to a predetermined impeller geometry;
curing the composite material; and
removing the molds to leave the erosion resistant coating on the flow
path cavities of the composite impeller.
2 . The method of claim 1, wherein a manner of the covering of the
molds with the erosion resistant material depends on a mold material.
3 . The method of claim 1 or claim 2, wherein the composite
material includes a resin.
4 . The method of any preceding claim, wherein the molds are
made of a water-soluble material and the removing of the molds is performed
by dissolving in a water-based solution.
5 . The method of any preceding claim, wherein the covering of the
molds with the erosion resistant coating comprises:
coating the molds with a sealant;
applying a conductive paint over the sealant; and
plating the erosion resistant layer over the conductive paint.
6 . The method of any preceding claim, wherein the sealant is an
epoxy paint.
7 . The method of any preceding claim, wherein the conductive
paint includes silver.
8 . The method of any preceding claim, wherein the plating of the
corrosion layer comprises:
plating a Ni-based layer over the conductive paint; and
plating the erosion resistant layer over the Ni-based layer using
electroless nickel plating (ENP).
9 . The method of any preceding claim, wherein the plating of the
Ni-based layer over the conductive paint is performed using a Woods nickel
strike.
10 . The method of any preceding claim, wherein the Ni-based layer
over the conductive paint has a thickness of less than 1 mil.
11. The method of claim 8, wherein the erosion resistant layer
plated using ENP includes diamonds of less than 2 size, in a proportion
around 35% by volume.
12 . The method of any preceding claim, wherein the molds are
made of a metal and the removing of the mold is performed by dissolving in
an acid solution or in a basic solution.
13 . The method of any preceding claim, wherein the molds are
made of copper or mild steel.
14. The method of any preceding claim, wherein the removing of the
mold is performed by dissolving in nitric acid.
15 . The method of any preceding claim, wherein the covering of the
molds with the erosion resistant coating is performed by thermal spraying.
16 . The method of any preceding claim, wherein the erosion
resistant coating is made of a ceramic and a metallic glue.
17 . The method of any preceding claim, wherein (a) the ceramic is
WC and the metallic glue is one of (i) a combination of Co and Cr, (ii) Ni, or
(iii) a combination of Ni and Cr, or (b) the ceramic is C 2C 3 and the metallic
glue is a combination of Ni and Cr.
18 . The method of any preceding claim, wherein the erosion
resistant coating has a thickness of at least 10 mil.
19 . An impeller, comprising:
blades;
a shroud in contact with the blades and having flow path cavities
therethrough; and
an erosion resistant coating on the flow path cavities, the erosion
resistant coating being made by
providing water-soluble molds having shapes corresponding to a
negative geometry of flow path cavities;
coating the molds with a sealant;
applying a conductive paint over the sealant;
plating an erosion resistant layer over the conductive paint;
shaping a composite material around the molds covered with the
sealant, the conductive paint and the erosion resistant coating,
according to a predetermined geometry;
curing the composite material; and
dissolving the molds in a water-based solution while leaving at
least the erosion resistant coating on the flow path cavities of the
impeller.
20. An impeller, comprising:
plural blades;
a shroud in contact with the blades and having flow path cavities
therethrough; and
an erosion resistant coating on the flow path cavities, the erosion
resistant coating being made by
providing metallic molds having shapes corresponding to a
negative geometry of the flow path cavities;
covering the molds with an erosion resistant coating using
thermal spraying;
shaping a composite material around the molds covered with the
erosion resistant coating, according to a predetermined impeller
geometry;
curing the composite material; and
dissolving the molds in an acid solution or in a basic solution,
while leaving the erosion resistant coating on the flow path cavities of
the impeller.