Patent Application
20250163814
This application is related to and claims all available benefit of Indian Provisional Patent Application IPA: 202311078198 filed Nov. 17, 2023, the entire contents of which are herein incorporated by reference.
The present disclosure generally relates to wheels for turbo-devices, for example, turbochargers, turbines or turbomachines, and/or the like. More particularly, the present disclosure relates to wheels having a bi-layered coating formed thereon and methods for making the same.
Turbo-devices can be used in a variety of applications. For example, turbochargers for gasoline and diesel internal combustion engines are devices known in the art that are used for pressurizing or boosting the intake air stream, routed to a combustion chamber of the engine, by using the heat and volumetric flow of exhaust gas exiting the engine. Another example includes turbines or turbomachines for fuel cells. The turbine may be operatively connected to a fuel cell system and may be configured as an e-charger, electric turbocharger, or other turbo-device for the fuel cell.
In the case of turbochargers for internal combustion engines, the exhaust gas exiting the engine is routed into a turbine housing of a turbocharger in a manner that causes an exhaust gas-driven turbine wheel to spin within the housing. The exhaust gas-driven turbine wheel is mounted onto one end of a shaft that is common to a radial air compressor mounted onto an opposite end of the shaft and housed in a compressor housing. Thus, rotary action of the turbine wheel also causes the air compressor to spin within a compressor housing of the turbocharger that is separate from the turbine housing. The spinning action of the air compressor causes intake air to enter the compressor housing and be pressurized or boosted to a desired amount before it is mixed with fuel and combusted within the engine combustion chamber.
In recent years, there has been increasing pressure in the form of governmental legislation to reduce internal combustion engine emissions, such as NOx and particulate matter (PM). Oxides of nitrogen (NOx) may be formed when temperatures in the combustion chamber are about 2500° F. or hotter. At these elevated temperatures, the nitrogen and oxygen in the combustion chamber may chemically combine to form nitrous oxides.
Exhaust gas recirculation (EGR) is a method that has been used to reduce the level of NOx in exhaust gases. In EGR systems, some of the exhaust gases that would otherwise be discharged into the environment are recirculated into the intake stream. The recirculated exhaust gases have already combusted and have a significantly lower oxygen content, so they do not burn again when they are recirculated. The exhaust gases may displace some of the normal intake charge. As a result, the combustion process may be cooler by several hundred degrees so that NOx formation may be reduced.
The use of EGR, however, results in an increased amount of water that is condensed out of the recirculated exhaust gases. The amount of water that is condensed may depend, for example, on temperature, humidity, and operating speed of the engine. When present, the condensed water droplets in the intake stream are passed through an inlet and impact the spinning compressor wheel, and as a result, an erosive effect may be observed over time. This can cause the components to prematurely fail.
Similarly in turbines for fuel cells, when present, condensed water droplets in the intake stream are passed through an inlet and impact the spinning fuel cell turbine wheel, and as a result, an erosive effect may also be observed over time. As a result, such components as well may prematurely fail.
Accordingly, it is desirable to provide wheels for turbo-devices that are able to withstand the erosive effects of water droplets, without requiring the use of heavier and relatively expensive materials. Furthermore, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description of the inventive subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the inventive subject matter.
Wheels having a bi-layered coating formed thereon and methods for making the same, are disclosed herein.
In an exemplary embodiment, a wheel includes a hub portion configured to rotate about a rotational axis. A plurality of blades extends radially outward from the hub portion. Each blade of the plurality of blades includes a leading edge and a trailing edge. The hub portion and the plurality of blades include a substrate metal. The substrate metal of the plurality of blades has coated directly thereon a first coating layer including electroless nickel-phosphorous having a phosphorous content of about 4 wt. % or greater. The first coating layer has coated directly thereon overlying the plurality of blades a second coating layer including electroless nickel-phosphorous poly-alloy having a phosphorous content that is lower than the phosphorous content of the first coating layer, wherein the second coating layer is a functional coating layer with enhanced erosion resistance.
In another exemplary embodiment, a wheel includes a hub portion configured to rotate about a rotational axis. A plurality of blades extends radially outward from the hub portion. Each blade of the plurality of blades includes a leading edge and a trailing edge. The hub portion and the plurality of blades include a substrate metal that includes aluminum or an alloy thereof. The substrate metal of the plurality of blades has coated directly thereon a first coating layer including electroless nickel-phosphorous having a phosphorous content of about 4 wt. % or greater. The first coating layer has coated directly thereon overlying the plurality of blades a second coating layer including electroless nickel-phosphorous poly-alloy having a phosphorous content of about 1 to about 1.5 wt. %, a cobalt content of about 0.5 to about 1.5 wt. %, and a tungsten content of about 0.05 to about 0.6 wt. %, wherein the second coating layer is a functional coating layer with enhanced erosion resistance.
In another exemplary embodiment, a method for making a wheel includes providing a substrate wheel. The substrate wheel includes a hub portion configured to rotate about a rotational axis, and a plurality of blades extending radially outward from the hub portion. Each blade of the plurality of blades includes a leading edge and a trailing edge. The hub portion and the plurality of blades include a substrate metal that includes aluminum or an alloy thereof. The method further includes forming on the substrate metal a first coating layer including electroless nickel-phosphorous having a phosphorous content of about 4 wt. % or greater. Forming the first coating layer includes immersing the substrate wheel in a first electroless nickel-phosphorous plating bath that includes nickel cations and phosphorous oxide anions. The method further includes forming on the first coating layer a second coating layer and includes electroless nickel-phosphorous poly-alloy having a phosphorous content that is lower than the phosphorous content of the first coating layer on the first coating layer. Forming the second coating layer includes immersing the substrate wheel with the first coating layer in a second electroless nickel-phosphorous plating bath that includes nickel cations, phosphorous oxide anions and other alloy ions and subsequently, exposing the substrate wheel including the first and second coating layers to a heat treatment process to thereby increase a hardness of the second coating layer as a functional coating layer with enhanced erosion resistance.
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
The inventive subject matter will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein:
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. As used herein, the word “exemplary” means “serving as an example, instance, or illustration.” Thus, any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described herein are exemplary embodiments provided to enable persons skilled in the art to make or use the invention and not to limit the scope of the invention which is defined by the claims. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary, or the following detailed description.
Unless specifically stated or obvious from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 5%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. “About” can alternatively be understood as implying the exact value stated. Unless otherwise clear from the context, all numerical values provided herein are modified by the term “about.”
The present disclosure is generally directed to wheels for turbo-devices in which the wheels have a bi-layered coating disposed thereon and methods for making the same. In particular, the present disclosure addresses the aforementioned erosion problem with the use of a relatively medium range phosphorous content (e.g., about 4 wt. % or greater), electroless nickel-phosphorus as a coating base layer followed by a relatively low phosphorous content (e.g., about 1 to about 1.5 wt. %), electroless nickel-phosphorous poly-alloy coating top layer. The purpose of the relatively medium range phosphorous content, electroless nickel-phosphorus coating base layer is twofold. First, during the manufacturing process, the relatively medium range phosphorus content, electroless nickel-phosphorous coating base layer is applied as a flash layer to the substrate wheel that helps provide protection to the underlying substrate material e.g., aluminum or an aluminum alloy, for subsequent application of the relatively low phosphorous content, electroless nickel-phosphorous coating top layer, which is carried out in a mildly-acidic to alkaline bath (e.g., pH of about 6 to 9). Second, the base layer helps to minimize any difference in hardness between the relatively low phosphorous content, electroless nickel-phosphorous coating top layer, which has a relatively high hardness (about 800 HV or greater), and the relatively soft aluminum substrate. That is, a relatively hard coating top layer disposed directly on the soft aluminum substrate could potentially compromise fatigue properties of the wheel due to a poor combination of mechanical strength and coefficient of thermal expansion mismatch between the aluminum substrate and the coating top layer.
As discussed above, the present disclosure utilizes the relatively low phosphorous content, electroless nickel-phosphorous as a coating top layer. In an exemplary embodiment, the electroless nickel-phosphorous coating top layer is a poly-alloy functional layer and is further alloyed with cobalt (e.g., about 0.5 to about 1.5 wt. %) and tungsten (e.g., about 0.05 to about 0.6 wt. %) that help in maintaining a compressive residual stress in the coating and also helps to increase hardness of the coating achieved after heat treatment, for example, at a temperature of about 175 to about 250° C. for a time of about 0.5 to about 4 hours. In an exemplary embodiment, ensuring a compressive residual stress in the coating helps to reduce potential issues of the wheel due to fatigue. Further, providing additional hardness (e.g., about 800 HV or greater) to the coating top layer helps the wheel including particularly the blades to withstand the erosive effects of water droplets, without requiring the use of heavier and relatively expensive materials.
Referring to
As illustrated, the wheel 10 is operatively disposed in the turbo-device 12 between an inlet 18 and an outlet 20 to rotate (indicated by single headed arrow 13) about a rotational axis 22. The wheel 10 is a radial wheel that includes a hub portion 24 and a plurality of blades 26 that extend radially outward from the hub portion 24. The blades 26 have a backward curvature rather than being configured to extend in a purely radial blade configuration. Each blade 26 includes a leading edge 28 that is in fluid communication with the inlet 18 and a trailing edge 30 that is in fluid communication with the outlet 20. The leading edges 28 define the beginning of an intake area for the combined set of blades 26, extending through the circular paths of roughly the upstream ⅓ of the blades 26. The trailing edges 30 define the end of an annular output area for the combined set of blades 26, extending through the circular paths of roughly the downstream ⅓ of the blades 26.
During operation of the turbo-device 12, the wheel 10 rotates about the rotational axis 22 and the leading edges 28 receive intake air that passes through the inlet 18 and advances rearwardly (indicated by single headed arrow 32) along the blades 26 towards the trailing edges 30. As such, the leading edges 28 are positioned longitudinally forward of the trailing edges 30 of the blades 26 with respect to the rotational axis 22 and the flow of air 32 along the wheel 10. As noted above, the wheel 10 is a turbocharger compressor wheel 16 in which the blades 26 are configured to compress the intake air to form compressed or pressurized air. The pressurized air passes from the trailing edges 30 and is ejected out through the outlet 20.
In some embodiments, the hub portion 24 and the blades 26 are formed of a substrate metal 36, such as, aluminum or an aluminum alloy, for example, via a casting and/or machining process. The wheel 10 is provided with a first (base) coating layer 34 on and overlying the substrate metal 36 and includes or is formed of electroless nickel-phosphorous. The phosphorous content of the first coating layer 34 may be greater than or equal to about 4 wt. %, for example from about 4 to about 9 wt. %, such as from about 5 to about 8.5 wt. %, such as about 6 to about 8 wt. %, for example about 7 wt. %. In an exemplary embodiment, the nickel content of the first coating layer 34 is less than or equal to about 96 wt. %, such, from about 91 to about 96 wt. %, for example, from about 91.5 to about 95 wt. %.
In an exemplary embodiment, the first coating layer 34 is a flash coating layer, or relatively thin coating layer, having a thickness from about 1 to about 5 microns, for example about 3 microns. The first coating layer 34 may be provided on all or most of the surfaces of the wheel 10, both forward and rear facing. If the first coating layer 34 is not provided on all of the surfaces, the surfaces not coated with the first coating layer 34 may include functional surfaces, such as portions of the back facing hub portion 24 about the centerline (axis of rotation 22) or portions of the forward-facing hub portion 24.
The wheel 10 is provided with a second (top) coating layer 38 on and overlying the first coating layer 34 and includes or is formed of electroless nickel-phosphorous poly-alloy that has a phosphorous content that is lower than the phosphorous content of the first coating layer 34. In an exemplary embodiment, the phosphorous content of the second coating layer 38 is less than about 4 wt. %, for example from about 1 to about 1.5 wt. %. In an exemplary embodiment, the nickel content of the second coating layer 38 is from about 97 to about 98 wt. %. In one or more embodiments of the present disclosure, the second coating layer 38 is a poly-alloy functional layer and further has a cobalt content of about 0.5 to about 1.5 wt. % and a tungsten content of about 0.05 to about 0.6 wt. %.
In an exemplary embodiment, the second coating layer 38 has a thickness from about 20 to about 25 microns. The second coating layer 38 may be provided overlying the first coating layer 34 on all or most of the surfaces of the wheel 10, both forward and rear facing. In an exemplary embodiment, if the first coating layer 34 is not provided on all of the surfaces neither will be second coating layer 38. For example, if the surfaces not coated with the first coating layer 34 include portions of the back facing hub portion 24 about the centerline (axis of rotation 22) or portions of the forward-facing hub portion 24, then neither will the same portions of the back facing hub portion 24 or portions of the forward-facing hub portion 24 be coated with the second coating layer 38. In one or more embodiments, the first and second coating layers 34 and 38 are coated on the blades 26 and extend overlying the substrate metal 36 of the hub portion 24.
In an embodiment, the second coating layer 38 has a hardness of about 800 HV or greater. Some embodiments, the second coating layer 38 is a hardness of about 800 HV to about 1000 HV. As will be discussed in further detail below, in some embodiments, the wheel 10 has been subjected to a heat treating process after deposition of the electroless nickel-phosphorous that forms the second coating layer 38 to improve the hardness of the second coating layer 38 to enhance erosion resistance.
Referring to
In particular, the wheel 100 including the rotational axis 122, the hub portion 124, the blades 126, the leading edges 128, the trailing edges 130, the substrate metal 136, the first coating layer 134, and the second coating layer 138 are similarly configured to the wheel 10 as discussed above in relation to
Referring to
The method 200 continues with a step 204 of forming (e.g., via depositing) a first (base) electroless nickel-phosphorous coating layer onto the substrate metal of the substrate wheel. Electroless nickel-phosphorus plating is a chemical process that deposits an even layer of nickel-phosphorus alloy on the surface of the substrate metal. The process involves dipping the substrate wheel in a water solution containing a nickel salt and a phosphorus-containing reducing agent, for example a hypophosphite salt. The concentration of the phosphorous-containing reducing agent is selected so as to achieve a phosphorous amount in the first coating layer greater than or equal to about 4 wt. %, and a nickel amount in the first coating layer less than or equal to about 96 wt. %, as described above. The reduction of the metal cations in solution to metallic form is achieved by purely chemical means, through an autocatalytic reaction. Before plating, the surface of the substrate may be cleaned. Cleaning may be achieved by a series of chemical baths, including non-polar solvents to remove oils and greases, as well as acids and alkalis to remove oxides, insoluble organics, and other surface contaminants. Further, functional portions of the substrate metal, as described above, may be optionally masked. Ingredients of the electroless nickel plating bath include a source of nickel cations Ni2+, for example nickel sulfate and a suitable reducing agent, such as hypophosphite H2PO3−. The plating bath may further include complexing agents, such as carboxylic acids or amines; stabilizers, such as lead salts or sulfur compounds; buffers; surfactants; and accelerators. In an exemplary embodiment, the plating bath has a pH of about 4 to about 5. The plating process is controlled with temperature and time to achieve a desired uniform thickness of about 1 to about 5 microns, as described above. In an exemplary embodiment, the substrate wheel is immersed in the plating bath for a time of about 20 to about 40 minutes, for example about 30 minutes. Once Ni—P plating is complete, the substrate metal, now having the first coating layer plated thereon, may be rinsed to remove any residues from the plating process, and the masking (if any) may be removed.
The method 200 continues with a step 206 of forming (e.g., via depositing) a second (top) electroless nickel-phosphorous coating layer over the first Ni—P layer via a second plating bath. The second plating bath is a water solution containing a nickel salt and a phosphorus-containing reducing agent, for example a hypophosphite salt. The concentration of the phosphorous-containing reducing agent is selected so as to achieve a phosphorous amount in the second coating layer less than about 4 wt. %, for example about 1 to about 1.5 wt. %, and a nickel amount in the second coating layer of about 97 to about 98 wt., as described above.
Further, the second plating bath contains other alloying ions including cobalt cations so as to achieve a cobalt amount in the second coating layer of about 0.5 to about 1.5 wt. %, and tungsten cations so as to achieve a tungsten amount in the second coating layer of about 0.05 to about 0.6 wt. % and is at a pH of about 6 to about 9. In an exemplary embodiment, the substrate wheel with the first coating layer disposed thereon is immersed in the second plating bath for a time of about 130 to about 170 minutes, for example about 150 minutes.
The method 200 may include performing various finishing processes, such as final cleaning, polishing, machining, heat treatment at temperatures. In an exemplary embodiment, the method includes exposing the substrate wheel including the first and second coating layers to a heat treatment process to thereby increase hardness of the second coating layer. In an exemplary embodiment, the heat treatment process includes exposing the substrate wheel including the first and second coating layers to a temperature of about 175° C. to about 250° C., such as about 195° C. to about 240° C., for example about 230° C., for a time of about 0.5 to about 4 hours, such as about 1 to about 4 hours, for example about 1 hour. The result is a wheel 10, 100 in accordance with that described above in connection with
While at least one exemplary embodiment has been presented in the foregoing detailed description of the inventive subject matter, 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 inventive subject matter 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 inventive subject matter. 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 inventive subject matter as set forth in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202311078198 | Nov 2023 | IN | national |
