NOZZLE ASSEMBLY FOR COLD SPRAY

A nozzle assembly is provided that includes two sections, the first section may be contoured and the second section may be a converging and diverging section that is downstream from the second section in the direction of gas flow. The contoured section, with a range of bend angles, allows for non-line-of-sight cold spray deposition, thereby providing location-specific control of the cold spray deposition process.

BACKGROUND

Cold spray deposition is a material deposition technique that enables powdered feedstock material to be heated, accelerated towards a target substrate, and eventually deposited in layers to build a coating. To achieve uniform thickness in the coating, the spraying nozzle may be scanned along the substrate in a line-of-sight process. Traditional nozzles that deliver powder or feedstock material for cold spray deposition are straight and are designed to accelerate the feedstock material, propelled by a high velocity gas stream, towards the target substrate for maximum adhesion and/or cohesion. However, in many applications, the target substrate may have complex geometries (e.g., interior surfaces of pipes) and line-of-sight deposition is insufficient for these applications.

SUMMARY

This Summary is intended to introduce, in simplified form, a selection of concepts that are further described in the Detailed Description. This Summary is not intended to identify key 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. Instead, it is merely presented as a brief overview of the subject matter described and claimed herein.

Embodiments described herein are directed to a nozzle assembly, for use with cold spray equipment. The nozzle assembly includes two sections, one being a tubular section that may be contoured or bent (e.g., variable from 10 to 180 degrees) and the other being a converging and diverging section that is downstream in the direction of the gas flow from the tubular section. This nozzle assembly allows for non-line-of-sight cold spray deposition, thereby providing greater location-specific control of the cold spray deposition process.

In an embodiment, a nozzle assembly is provided that includes a first section that has a flanged end and a first coupling end, and a second section that has an internal converging section and an internal diverging section to allow powder particles to be accelerated toward a target substrate. The second section may include an output end of the nozzle assembly and a second coupling end configured to be coupled with the first coupling end.

Another embodiment is directed to a cold spray system. The system includes a cold spray gun and a nozzle assembly that includes a first section that has a flanged end and a first coupling end. The nozzle assembly further includes a second section that has an internal converging section and an internal diverging section to allow powder particles to be accelerated toward a target substrate, the second section comprising an output end of the nozzle assembly and a second coupling end configured to be coupled with the first coupling end.

Further features and advantages of the invention, as well as the structure and operation of various embodiments are described in detail below with reference to the accompanying drawings.

DETAILED DESCRIPTION

Definitions

In describing and claiming the disclosed embodiments, the following terminology will be used in accordance with the definition set forth below.

As used herein, the singular forms “a,” “an,” “the,” and “said” do not preclude plural referents, unless the content clearly dictates otherwise.

As used herein, the term “about” or “approximately” when used in conjunction with a stated numerical value or range denotes somewhat more or somewhat less than the stated value or range, to within a range of ±10% of that stated.

Terminology used herein should not be construed as being “means-plus-function” language unless the term “means” is expressly used in association therewith.

Overview

Cold spray is an emerging materials deposition process, first patented in the 1990s with accelerated development in the early 2000s. Cold spray allows for metallic and metallic-ceramic coatings to be formed from power feedstock material that is not melted. For cold spray, hot gasses are forced through a de Laval nozzle (a converging/diverging design) to accelerate deposition gas and entrapped feedstock particles towards a target ahead of the torch or cold spray gun opening. The accelerated feedstock particles are then deposited in layers on the target to build a coating. Typical nozzles are made from hard, brittle materials that are impossible or impractical to bend. Thus, because of the fabrication material and the converging/diverging (CD) design, these nozzles are traditionally configured to be straight.

One of the many longstanding challenges with cold spray deposition is the line-of-sight nature of the coating process, in contrast to other surface coating techniques like physical or chemical vapor deposition. Applications involving targets with complex geometries (e.g., interiors of pipes, valves, piping systems) or difficult to reach targets, would benefit greatly from a non-line-of-sight deposition process.

Embodiments described herein are directed to a nozzle assembly, for use with a cold spray system. In an example embodiment, the nozzle assembly includes two sections. The first section is one that may be contoured or bent (e.g., variable in degree), depending on the application. The first section may also be straight, with a bend degree of 0, if desired. The second section is a converging and diverging (CD) section (i.e., having an internal convergent and divergent design) that is downstream in the direction of gas flow from the first section. This nozzle assembly allows for non-line-of-sight cold spray deposition, thereby providing greater location-specific control of the cold spray deposition process and enable coating of otherwise hard to reach locations. These sections may be configured to have a range of bend angles, sizes, and lengths while still providing particle velocity control via fluid mechanics. In an example embodiment, the first and second sections may be directly coupled. In another example embodiment, the first and second sections may be coupled via an adapter and a coupling nut.

Because the gas stream of the cold spray process can be relatively easily controlled with conduit geometry and because small size particles tend to follow the gas flow contour, especially when constrained radially, it is possible to tailor the nozzle shape (e.g., bend angle) to allow for angled particle flow. Additionally, by locating the CD feature downstream of the bend radius, particle flow is ensured as the gases and feedstock particles do not have to flow through a bent or contoured section of the nozzle assembly in an accelerated state. The CD feature placement also improves the life and performance of the nozzle assembly as the contoured section is not subjected to the acceleration of particles and gases, which occurs in the CD section that is downstream from the contoured section.

Accordingly, the nozzle assembly with a variable bend allows for targeted deposition in areas where the prior line-of-sight straight nozzle approach is not sufficient. Bent nozzles also allows for targeted material deposition in hard to reach locations, resulting in increased adhesion and cohesion strengths that straight nozzles are not able to obtain. The nozzle assembly may be configured with multiple sections (not just two) to allow for greater flexibility and deposition control. Furthermore, the different sections of the nozzle assembly are not limited in size or length, and may be varied in lengths and diameters compared to typical cold spray nozzles to accommodate higher pressure air or gas of various composition and/or allow for either fine area or wide area deposition.

The nozzle assembly may be adapted with an air-cooled heat exchanger (e.g., U.S. patent application Ser. No. 17/354,780 filed on Jun. 22, 2021, entitled “Cooling System and Fabrication Method thereof,” the entirety of which is incorporated herein by reference) for additional particle kinetic energy control with higher gas temperatures. In addition, the nozzle assembly may be used in a cold spray process that has an accompanying post-treatment process (e.g., U.S. patent application Ser. No. 17/242,445 filed on Apr. 28, 2021, entitled “Post-Treatment via Ultrasonic Consolidation of Spray Coatings,” the entirety of which is incorporated herein by reference).

FIG.1depicts an orthogonal view of a nozzle assembly100, according to an embodiment. Nozzle assembly100may include a first section102that is tubular and has two ends. One end of first section102is configured to be connected to a second section104and the other end is configured to be connected to coupling nut106.

FIG.2depicts a cross-sectional view along line C-C of nozzle assembly100ofFIG.1. Nozzle assembly200shown inFIG.2may include first section202that is directly coupled to second section204and coupling nut206. First section202may include a first coupling end208and a flanged end210. Second section204may include a second coupling end220and an output end216, which is the output of nozzle assembly200, from which gases and feedstock particles may be discharged to form a coating on a target.

To couple first section202to second section204, first coupling end208and second coupling end220may be connected together in a tight fit such that the connecting surfaces are as close together as possible. In an embodiment, second coupling end220may be configured to receive first coupling end208. For example, second coupling end220may include internal threads and a larger diameter for receiving first coupling end208, which may include external threads, as shown inFIG.2. Thus, the external and internal threads are configured to lock first section202and second section204together. First coupling end208and second coupling end220may be pitched so that the external shoulder of first section202is flushed against the internal shoulder of second section204such that there is no gap between the two sections or any disparities in the connecting surfaces that may trap particles or promote build up inside the nozzle assembly.

In an embodiment, coupling nut206may be placed on first section202and slid down its length to form a tight fit with flanged end210before first section202is coupled to second section204. This is because the external diameter of second coupling end220may be too large, and therefore would not allow coupling nut206to pass through from output end216to flanged end210. In an embodiment, a sealant and/or a gasket may be placed adjacent to the second coupling end220, between first section202and second section204to secure the two sections together and prevent leakage. In another embodiment, a fastening and/or locking means, such as an adhesive (e.g., Loctite® threadlocker), may be placed on connecting surfaces of first section202and/or second section204to lock and seal the two sections together. In other embodiments, other means of coupling the different components of nozzle assembly200may be utilized.

As shown inFIG.2, second section204may include an internal converging section212connected to a throat218that is connected to a diverging section214. Thus, second section204may also be referred to as the converging and diverging (CD) section. Coupling nut206is configured to connect first section202to a cold spray system via flanged end210. Coupling nut206may include a countersunk hole or a counterbored hole to allow it to slide up the length of first section202and stop at flanged end210.

FIG.3depicts an example cold spray system300. System300may include, among other components not shown inFIG.3, a cold spray torch or gun302coupled a nozzle assembly304. A coupling nut, such as coupling nut206shown inFIG.2, may be used to couple nozzle assembly304to cold spray gun302. In operation, cold spray system300may be utilized for solid-state powder deposition, which involves accelerating powder feedstock particles (e.g., 10-100 μm in size) through nozzle assembly304with a compressible carrier gas (e.g., helium, nitrogen or air) or a combination of gases to achieve supersonic gas velocities for favorable deposition of coating layer(s) on a target306. Target306may be a substrate or any surface to be repaired, enhanced, or modified in some manner, including a surface that has previously been coated. For example, the substrate may be a surface of a piece of field equipment, rotating components (e.g., shafts, rollers, etc.), hydraulic parts, engines, turbines, cavities, or medical devices to be repaired, enhanced, or manufactured.

Feedstock materials for cold spray include pure metals (e.g., aluminum, nickel, copper, or titanium), metal alloys, polymers, and hybrid materials (e.g., metal-metal, metal-alloy, metal-ceramic, or metal-graphene/carbon nanotubes). These materials allow for the application of different coatings, for example, to repair a component with similar or improved materials or to form desired features into the cold spray coatings deposited on a substrate or a target surface of the component. Modifying or repairing a component may be a more economical choice than replacing that component. The cold spray process may be a useful alternative for brush plating, electroplating, weld repairs, etc., because it is a quick process and can build material reliably in a relatively short time.

The internal geometries of nozzle assembly304, particularly, the CD section is designed to convert heat energy of the carrier gas and feedstock powder flow into kinetic energy. The carrier gas, at an established pressure and temperature, enters nozzle assembly304CD section, specifically the converging section, which compresses the gas at subsonic velocity through its length until the gas reaches the constriction or throat (e.g., through218shown inFIG.2). The particle velocity is relatively slow at this location, compared to the gas velocity, and the particles continue to absorb heat from the carrier gas. As the gas exits the throat and enters the diverging section of the CD section, pressure and temperature reduce, while velocities increases to near or supersonic velocities. Particles may accelerate in the gas stream from the end of the throat to nozzle exit (e.g., output end216shown inFIG.2), where compressible gas velocities, Vg, follow equation 1:

where R is the specific gas constant, T is the temperature, γ is the specific heat ratio (e.g., 1.4 for diatomic nitrogen, and 1.66 for monatomic helium), and M is the Mach number. Gas velocities may also be influenced by aspects of the nozzle throat as follows.

where A is the calculated cross-sectional area along the nozzle, and A* is the area of the nozzle throat. Employing gas stream velocities, pressures, and temperatures, the particle velocity (Vp) may be modeled based on the estimated particle drag coefficient (Cd), mass of the particle (m), gas velocity (Vg), cross sectional area of a particle (Ap), and the assumption that the particle velocity is much less than the gas velocity, as follows.

where ρgis the gas density. Particle drag is dependent on particle density, size and shape, where the larger or the more irregular the shape, drag increases and particle velocity or kinetic energy decreases. This aspect is important, especially when carrier gas temperatures and pressures are low, such as for portable cold spray systems. Additionally, the particle temperature is subsequently lower than its melting point upon exit from the nozzle, thus resulting in limited oxide formation, in contrast to inflight particles of many thermal spray processes. This is a desirable aspect of cold spray, where the feedstock properties are retained during deposition and particle exit velocities can range from 500-1200 m/s. The basis of particle velocity and momentum create the relatively high kinetic energy, coupled with the cold spray fluid mechanics, which is the driving force for the critical velocity window of deposition, determine coating adhesion, cohesion, and deposit compaction and efficiency. The solid-state particle undergoes deformation and adiabatic shear instability as it impacts and craters into the target substrate, which consequently results in substrate deformation, improving first layer adhesion.

As shown inFIG.2, first section202is a straight section. However, in other embodiments, section202may be a contoured section with a variable degree of bend (e.g., 10°, 20°, 45°, 90°, 180°, 360°) with no limitation on the bend angle. This enables the nozzle assembly to deposit material in a non-line-of-sight process, particularly useful for hard to reach locations and/or on components with complex geometries not suitable for line-of-sight deposition. For example,FIGS.4-7illustrate different embodiments of the nozzle assembly described herein, each of which includes a contoured section upstream from a CD section.

FIG.4depicts an orthogonal view of a nozzle assembly400with a contoured section.FIG.5depicts a cross-sectional view of nozzle assembly400shown inFIG.4. Nozzle assembly500shown inFIG.5includes first section502, second section504, and coupling nut506. As shown inFIG.5, first section502is a contoured section with a bend angle of 90°.

FIG.6depicts an orthogonal view of a nozzle assembly600with a contoured section.FIG.7depicts a cross-sectional view of nozzle assembly600shown inFIG.6. Nozzle assembly700shown inFIG.7includes first section702, second section704, and coupling nut706. As shown inFIG.7, first section702is a contoured section with a bend angle of 180°.

The embodiments shown inFIGS.4-7are intended to be example embodiments and are not intended to be limiting. The sizes/diameters (internal and external), lengths, bend radius or angle of bend for each section may be configured for a particular application and/or to control particle velocity via fluid mechanics, governed by the above equations. The nozzle assembly may be configured in any logical manner, for example, more than two sections may be connected together in a series as long as they do not become too cumbersome as to inhibit gas and/or particular flow. In this case, the ends of the different sections may need to be adapted such that the desired sections may be appropriately joined together with a first section connected to a coupling nut and with the last section being a CD section, with respect to the direction of gas/particle flow. For example, in a nozzle assembly with three sections, the middle section may be a straight or contoured section with internal threads on one end and external threads on the other end.

One challenge with the cold spray process is that there is a propensity for accelerated particles to stick to or adhere or adsorb onto the internal walls of the cold spray nozzle. This is typically an issue for softer metallic materials, such as aluminum and copper, or when higher operating temperatures are used for cold spray. One way to address this challenge is to apply a protective treatment to the surfaces of one or more sections of the nozzle assembly to reduce particular sticking via case-hardening or hardfacing. Such treatment may also reduce wear-and-tear of the treated surfaces as the treatment may be erosion and/or corrosion resistant. In addition, such treatment and/or the choice of material from which the nozzle assembly is fabricated, may have an effect on process characteristics, such as materials compatibility or wettability. Thus, in embodiments, a treatment configured to produce a certain effect, such as to improve wear properties and/or to reduce degradation and particle sticking, or to impact process characteristics, may be provided on one or more internal or external surfaces of one or more sections of the nozzle assembly. For the hardfacing process, many materials may be utilized, for example, nitride, titanium nitride, boron nitride, or diamond-like carbon. It may be more beneficial to apply such treatment to the internal walls of the different sections of the nozzle assembly, especially if the material or process is costly or time consuming and thus should be utilized sparingly. For example, it may be more economical and efficient to replace a section (e.g., a non-CD section) rather than spend the resources to protect that section with a treatment. However, in certain applications (e.g., harsh operating environments), the exterior surfaces may benefit from such treatment. Different surfaces and/or sections may undergo the same or different treatments, depending on the application.

The different sections of a nozzle assembly will be described below in connection withFIGS.8-16.FIG.8depicts an orthogonal view of a CD section800of a nozzle assembly.FIG.9depicts a cross-sectional view of CD section800shown inFIG.8. As shown inFIG.9, CD section900includes a threaded end902, with internal threads, configured to receive the externally threaded end of another section. CD section900also includes output end904, from which gas(es) and feedstock particles are discharged onto a target substrate. CD section900may be made from a metal or metal alloy (e.g., carbon steel, stainless steel, tungsten carbide) via any suitable process, for example, machining, extrusion, etc. As CD section900have to withstand the acceleration of gases and particles at high velocities, the material(s) used for fabricating may be wear-resistant. As mentioned above, the sizes/diameters and lengths of CD section900may be customized for different applications with no limitation beyond what is required to maintain process control (e.g., velocity control) via fluid dynamics. As shown inFIG.9, CD section900may include an exterior chamfered edge906at threaded end902and an exterior filleted edge908at a predetermined distance (e.g., 0.723 inches) down the length of CD section900. CD section900may also include a threaded portion910. In embodiments, threaded portion910may be configured in any manner and/or standard, for example, with ¼″-18 NPTF. In an embodiment, the interior diameter of threaded portion910may be 0.375 inches with a length of 0.473 inches. CD section900may also include a converging section912(e.g., 0.787 inches in length), a throat section914(0.197 inches in length and 0.106 inches in diameter), and a diverging section916(e.g., 0.244 inches in diameter at output end904). The length of diverging section916may vary, depending on the application, and may include example lengths of 1.5, 2.5, 4.016 or 5.516 inches. The length of diverging section916and the diameter at output end904may be varied, individually or in combination, to allow for fine area or wide area deposition and/or usage of different types and/or composition of gases.

FIGS.10-12illustrate different views of a contoured section of a nozzle assembly.FIG.10depicts an orthogonal view of a section, configured to have a variable bend degree, of a nozzle assembly. As shown inFIG.10, the bend degree of contoured section1000is 45°.FIG.11depicts a perspective view of contoured section1000ofFIG.10. As shown inFIG.11, contoured section1100is configured to be tubular with substantially the same internal diameter throughout its length.FIG.12depicts a cross-sectional view along line D-D of contoured section1100shown inFIG.11. Contoured section1200shown inFIG.12includes a flanged end1202and an externally threaded end1204, configured to be received by another section (e.g., a CD section) for coupling the two sections together. Flanged end1202may be coupled to a cold spray system via a coupling nut.

Contoured section1200may be made from a metal or metal alloy (e.g., carbon steel, stainless steel, etc.) that is pliable and/or ductile to allow for bending. Feedstock particles may flow into contoured section1200from the cold spray system at a relatively slow speed and may be fairly warm. As the particles travel downstream, they cool off and accelerate in velocity at the CD section. Thus, contoured section1200does not have to have high tolerance against wear or particle sticking as the particles do not tend to stick if they move slowly. Accordingly, contoured section1200may be made from readily available and/or inexpensive materials via a suitable process (e.g., machining, extrusion, etc.) In this sense, contoured section1200may be considered a consumable part that is relatively easy to replace in comparison with the CD section.

As shown inFIG.12, flanged end1202may include exterior chamfered edges1206and1208and have an opening1210with a predefined exterior diameter (e.g., 075 inches). Flanged end1202may include collar1212that serves as an attachment point for connecting contoured section1200to the body of a cold spray gun. Collar1212may have a particular length (e.g., 0.25 inches). The size and/or shape of flanged end1202and collar1212may be configured for a particular cold spray system (i.e., cold spray equipment specific) as different cold spray systems may have their own configurations. The external diameter of contoured section1200may be, for example, 0.6 inches. Contoured section1200may include two flattened areas1214and1216(e.g., 0.25, 0.375, 0.464, or 0.5 inches in length and 0.267 in width) usable as anchor and/or leverage points to tighten contoured section1200with another section. Contoured section1200may be configured to be straight for a predefined length (e.g., 1.8 inches) before it is bent, for example, with a bend radius of 3 inches. Threaded end1204may include a portion (e.g., 0.438 inches) that is externally threaded in any manner and/or standard, for example, with ¾″-18 NPTF. Threaded end1204may include opening1218(e.g., 0.375 inches in diameter).

The contoured section shown inFIGS.10-12is merely an example. As the bend may be variable from 0° and above, other configurations of contoured section may be utilized for a nozzle assembly. Non-limiting examples of contoured sections are provided inFIGS.13-16.FIG.13depicts a cross-sectional view of a section with bend degree of 0.FIG.14depicts an orthogonal view of a section with bend degree of 20.FIG.15depicts an orthogonal view of a section with bend degree of 90.FIG.16depicts a cross-sectional view of a section with a bend degree of 180. In operation, efficiency may be improved by having multiple contoured sections, each with a particular bend degree, such that one contoured section may be replaced with another contoured section, depending on the desired application.

FIG.17depicts an exploded view of a nozzle assembly, according to an example embodiment. Nozzle assembly1700may include a first section1702, a first coupling nut1706, an adapter1710, a washer1712, a second coupling nut1708and a second section1704. In this embodiment, adapter1710is a female-male adapter, but any suitable adapter may be used to implement adapter1710. First coupling nut1706may be configured to be placed onto first section1702from first coupling end1728and moved up to flanged end1722before adapter1710is connected to first section1702. Washer1702may be placed into adapter1710before it is connected to section1704. Then, second coupling nut1708may be placed on second section1704at output end1716and moved up to flanged end1720, over adapter1710. In an embodiment, washer1702may be a sealing washer that is suitable for cold spray operation, i.e., can withstand the high temperature range of cold spray. In another embodiment, instead of or in addition to washer1702, an adhesive may be used.

FIG.18depicts an orthogonal view of the nozzle assembly ofFIG.17. As shown inFIG.18, nozzle assembly1800is a complete assembly of the various components shown inFIG.17.

For purpose of illustration and not intended to be limiting,FIGS.19-21depict various components of a nozzle assembly with specific dimensions. These various components may be assembled together to form a nozzle assembly that has a bend degree of 0.FIG.19depicts a cross-section view of a first section1900of a nozzle assembly.FIG.20depicts a cross-sectional view of an adapter2000.FIG.21depicts a cross-sectional view of a second section2100or CD section of a nozzle assembly.

CONCLUSION

While various embodiments of the disclosed subject matter have been described above, it should be understood that they have been presented by way of example only, and not limitation. Various modifications and variations are possible without departing from the spirit and scope of the described embodiments. Accordingly, the breadth and scope of the disclosed subject matter should not be limited by any of the above-described exemplary embodiments.