Plasma nozzle for thermal spray gun and methods of making and using the same

Abstract

The plasma nozzle includes a nozzle body arranged to engage with a thermal spray gun. The nozzle body includes an axial throughbore having an upstream input orifice and a downstream nozzle outlet, at least one material injector positioned between the upstream input orifice and the nozzle outlet, the at least one material injector configured to introduce a feedstock into a gas flow through the axial throughbore, and at least one gas injector configured to introduce a shroud gas flow into the axial throughbore and located at a position upstream of the at least one material injector.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority under 35 USC § 119(e) to U.S. Provisional Patent Application No. 62 / 635,735, filed on February 27, 2018. The disclosure of the U.S. Provisional Patent Application is expressly incorporated herein by reference in its entirety.

[0003] Statement Regarding Sponsored Research or Development

[0004] not applicable. Technical Field

[0005] The present invention relates to a plasma nozzle having a nozzle body arranged to engage with a thermal spray gun, wherein the nozzle body has an axial through hole with an upstream input orifice and a downstream nozzle outlet. The nozzle body also has one or more material injector openings positioned between the input orifice and the nozzle outlet for providing material, and one or more gas injector openings for providing shield gas flow. In an embodiment, the gas injector opening is positioned upstream relative to the material injector opening. A method of making and using the same is also disclosed. Background Art

[0006] Thermal spray coating materials are known and are typically metal and / or ceramic powder materials. Some of these powder materials provide wear resistance, corrosion resistance, and act as thermal barrier coatings when used to form thermal spray coatings.

[0007] Plasma spraying is a widely used process for depositing a wide range of such coating materials. Material is supplied as powder, suspension, solution or liquid, and is ejected into a hot highly ionized gas stream. Material is therefore melted or vaporized in the hot plasma, and is simultaneously accelerated toward the substrate by the plasma stream. In the case of vacuum plasma spraying (wherein the spraying equipment is operated at low ambient pressure inside the container), the injection occurs in the anode / nozzle inside of the plasma generator. This layout is called internal injection.

[0008] Figure 1A schematic diagram of a prior art plasma spray gun with internal injection is shown. With respect to the gas flow direction, upstream US refers to the direction of the plasma gas GF injection around the cathode CA, and downstream DS refers to the direction of the anode / nozzle outlet, which is located on the downstream end of the anode An in this example. In this device, a plasma arc A is formed by applying a voltage from a powder supply PS between the cathode CA and the anode An, which simultaneously guides the gas flow GF. The arc A moves in the direction of the anode axis and over the entire circumference with arbitrary motion, but remains upstream of the injection point PI of the powder or suspension. The powder injection port P is used to introduce powder in the form of powder particles PP into the plasma jet PJ. The nozzle includes a coolant flow CW, the action of which allows cooling water to cool the nozzle. This is described in U.S. Patent 6,322,856 granted to HISLOP, the disclosure of which is expressly incorporated herein by reference in its entirety. The process occurs at low ambient pressure and is called low pressure plasma spraying (LPPS) or vacuum plasma spraying (VPS). Under certain conditions described in EP Patent 2439306 (the disclosure of which is expressly incorporated herein by reference in its entirety), the material is partially or completely transferred into the gas phase. This process regime is known as plasma spray physical vapor deposition (PS-PVD).

[0009] Internal spraying is also used in suspension plasma spray (SPS) or solution precursor plasma spray (SPPS). Both processes can be operated in the atmosphere (atmospheric pressure) and in a controlled atmosphere at pressures as low as those described in, for example, US Pat. No. 8,986,792 to HOSPACH et al.

[0010] Internal injection allows for more efficient transfer of heat energy from the plasma to the injected material. This is particularly important in processes where the injected powder material (or particles in suspension) is carried into the gas phase or broken into nano-sized clusters or solvents must be removed. Without confinement of the plasma-material mixture, heat transfer would be inadequate and result in low process efficiency and poor coating properties.

[0011] These LPPS / VPS / PS-PVD and SPS / SPPS processes are mainly used in commercial applications to apply MCrAlY alloys, thermal barrier coatings made of ceramic materials or dense ceramic layers. See, for example, Handbook of Thermal Spray Technology, the disclosure of which is expressly incorporated herein by reference in its entirety.

[0012] Since the anodes in such devices are typically water-cooled, there is an opportunity for the material on the anode wall to recondense or solidify at locations downstream of the material injection point and around the injection port. The deposited material can cause damage to the coating process or completely interrupt it. The phenomenon of material adhering to the anode wall (and the outlet of the feed injector) is called clogging. The most critical issues caused by clogging are a) deflection of the plasma jet, b) embedding of material that separates from the anode and finds its way into the coating (see Handbook of Thermal Spray Technology), and c) complete plugging of the injection port.

[0013] Several prior art devices function by forming a shroud while spraying in the atmosphere around the plasma gas flow outside the anode (see articles by S. Matthews entitled Shrouded plasma spray of Ni-20Cr coatings utilizing internal shroud film cooling (https: / / www.sciencedirect.com / science / article / pii / S0257897214002679), by S. Yoon et al. entitled Tribological behavior of B4C reinforced Fe-base bulk metallic glass composite coating (https: / / www.sciencedirect.com / science / article / pii / S0257897210007279), by J. Li et al. entitled Effect of vapor deposition in shrouded plasma spraying on morphology, and wettability of the metallic Ni20Cr Coatingsurface (Effect of Vapor Deposition on Surface Morphology and Wettability of Metal Ni20Cr Coating in Shielded Plasma Spraying) (https: / / www.sciencedirect.com / science / article / pii / S0925838817338926) and EP2439306, the disclosure of which is expressly incorporated herein by reference in its entirety), or flame spraying around a flame (see US Pat. No. 5,285,967 to WEIDMAN, the disclosure of which is expressly incorporated herein by reference in its entirety) to protect the sprayed material from the surrounding environment (particularly from oxidation in the case of alloys or from burning in the case of plastics). In all those processes, the gas is injected in an extension mounted on the spray gun and thus occurs only downstream of the material injection point and outside the spray gun and outside the anode in the case of plasma processes. Figure 2 An example of a conventional plasma gun PG is schematically shown which uses a shroud gas flow which forms an internal shroud gas film ISGF along the inner wall of the shroud SH. The apparatus uses a powder jet PJ and a shroud gas jet ISI in conjunction with a powder trajectory PT to transform powder particles P into a coating material.

[0014] For most thermal spray processes, especially plasma spray processes, radial feed injection is placed outside the spray gun to avoid material accumulation on the nozzle and outlet of the spray gun, but this arrangement can be improved. For powder-based spray vacuum processes under working pressures below 100 mbar (and especially below 5 mbar), the spray plume expands radially once it leaves the constrained anode, which makes external injection unfeasible. In the case of suspension-based or solution-based spray processes, most of the transferred energy is absorbed, mainly to evaporate the solvent. As a result, in order to have a more efficient process for melting the feed, the injection of the material is completed inside the anode. At this position, due to the constraints from the anode wall, the plasma is denser and slower, resulting in longer residence time and higher heat transfer rate compared to the spray system with external injection of powder material.

[0015] Some plasma spray systems use an axial injection system for the feed material to allow internal injection into a denser, hotter plasma. However, this design suffers from two disadvantages. The first is that the injector is exposed to a higher heat flux, resulting in an increased likelihood of material accumulation on the injector itself (at the exit or also deeper inside the injector). The second is that using certain plasma parameter regimes or plasma gas compositions, the flow generated from the hot gas or plasma jet is turbulent, resulting in material deposition on the anode wall.

[0016] Because the plasma jet expands radially from the jet axis at the nozzle outlet, the vacuum type plasma spray process needs to have an internal injection of the material. The injection is radially toward the plasma jet relative to the plasma jet and can have an upstream or downstream direction between 45° and 135° relative to the jet axis. Optionally, the injection can also have a radial swirl between 0 and 20°, allowing the powder material to be injected radially but slightly offset from the center of the axis of the plasma jet.

[0017] In suspension type plasma spraying and solution precursor plasma spraying, the process is carried out in the atmosphere or in a controlled atmosphere at a minimum pressure of several millibars. In the latter case, the plasma gun and system are placed in a controlled atmosphere chamber, where the gas composition and pressure can be set and adjusted at a given pressure. The typical anode design for these applications does not usually include any shield forming gas inlet. However, atmospheric thermal spraying processes (such as atmospheric plasma spraying (APS), flame spraying (FS) or arc wire spraying) utilize shield gases generated by extensions or extension nozzles placed on the spraying device. They are characterized by shield gas inlets, which are located downstream of the feed injection, so that the volume around the gas jet containing the coating material is filled with an inert gas (such as nitrogen, argon or the like) to protect the spraying material from the surrounding air (especially oxygen). In this case, the shield gas injected is used so that it does not affect the hot gas flow and material flux inside the spray gun.

[0018] However, none of the above-mentioned prior art disclosures describe the use of anodes of the type presented herein to provide advantageous benefits. Summary of the invention

[0019] Embodiments of the present invention include a plasma nozzle comprising a nozzle body arranged to engage with a thermal spray gun, wherein the nozzle body includes: an axial throughbore having an upstream input orifice and a downstream nozzle outlet; at least one material injector positioned between the upstream input orifice and the nozzle outlet, the at least one material injector configured to introduce a feedstock into a gas flow through the axial throughbore; and at least one gas injector configured to introduce a shield gas flow into the axial throughbore and can be located at a position upstream of the at least one material injector.

[0020] The at least one gas injector may be an opening in a wall of the nozzle body and the at least one material injector is an opening in a wall of the nozzle body.

[0021] The at least one gas injector may be an opening in the wall of the nozzle body having a diameter or size that is smaller than the diameter of the at least one material injector.

[0022] At least one gas injector may be a first opening and at least one material injector is a second opening, and wherein the first opening is arranged in a semicircular area defined by 3 times the diameter of the second opening, and the radius of the area extends from the central axis of the second opening.

[0023] The first opening may include a plurality of openings spaced apart by the same amount from the central axis of the second opening.

[0024] The first opening may include a plurality of openings spaced apart from a central axis of the second opening by different amounts.

[0025] The second opening may include a plurality of openings.

[0026] The nozzle may also include at least one downstream gas injector positioned downstream of the at least one material injector.

[0027] The at least one downstream gas injector may include a plurality of downstream gas injectors positioned at an azimuth angle relative to a central axis of the axial throughbore.

[0028] The nozzle body may be the anode.

[0029] The nozzle body may be the anode of a thermal spray gun.

[0030] The present invention also includes a thermal spray gun comprising the plasma nozzle described above.

[0031] The present invention also includes a thermal spray gun plasma nozzle, which includes an anode, which includes: an axial through hole having an upstream input orifice and a downstream nozzle outlet; at least one material injector opening, which is positioned between the upstream input orifice and the nozzle outlet, and the at least one material injector opening is configured to introduce a feed into the gas flow through the axial through hole; and at least one gas injector opening, which is configured to introduce a shield gas flow into the axial through hole and is located at a position upstream of the at least one material injector opening, wherein the at least one gas injector opening is smaller in diameter than the at least one material injector opening.

[0032] The at least one gas injector opening may be arranged in a semicircular area defined by 3 times the diameter of the at least one material injector opening, with the radius of the area extending from a central axis of the at least one material injector opening.

[0033] The at least one gas injector opening may include a plurality of openings spaced from a central axis of the at least one material injector opening.

[0034] The at least one gas injector opening may include a plurality of openings spaced at different amounts from a central axis of the at least one material injector opening.

[0035] The present invention also includes a thermal spray gun plasma nozzle, which includes an anode, which includes: an axial through hole having an upstream input orifice and a downstream nozzle outlet; at least one material injector opening, which is positioned between the upstream input orifice and the nozzle outlet, and the at least one material injector opening is configured to introduce powder feed into the gas flow through the axial through hole; and at least one gas injector opening, which is configured to introduce an inert shield gas flow into the axial through hole and is located at a position upstream of the at least one material injector opening, wherein the at least one gas injector opening is smaller in diameter or size than the at least one material injector opening.

[0036] The at least one gas injector opening may be arranged in a semicircular or arcuate region defined by 3 times the diameter or size of the at least one material injector opening, with the radius of the region extending from a central axis of the at least one material injector opening.

[0037] The at least one gas injector opening may include a plurality of openings spaced from a central axis of the at least one material injector opening.

[0038] The at least one gas injector opening may include a plurality of openings spaced at different amounts from a central axis of the at least one material injector opening.

[0039] The present invention also includes a method of manufacturing a plasma nozzle of any of the types described above, wherein the method includes arranging at least one gas injector opening upstream of at least one material injector opening and in a semicircular area defined by 3 times the diameter of the at least one material injector opening, and the radius of the area extends from the central axis of the at least one material injector opening.

[0040] The present invention also includes a method of using a plasma nozzle of any of the types described above, wherein the method includes introducing an inert gas through at least one gas injector opening when introducing powder via at least one material injector opening, the at least one gas injector opening being located upstream of the at least one material injector opening and in a semicircular area defined by 3 times the diameter of the at least one material injector opening, and the radius of the area extending from the central axis of the at least one material injector opening.

[0041] Embodiments of the invention also include an anode and / or a nozzle having an anode that prevents material from accumulating near and downstream of the material injection port in the anode. This is achieved by injecting a small amount of gas compared to the total gas flow of the plasma jet near and downstream of the material injection. The injection area can extend from close to the injection point upstream to the anode outlet. This forms a thin layer of gas that flows along the anode wall and prevents material from being deposited on the inside of the anode.

[0042] Embodiments of the present invention include anodes and / or nozzles having anodes in which the gas shroud generated in the anode acts like a shield and protects the anode wall from the sprayed material. As a result, the configuration prevents feedstock from accumulating on the anode wall. This results in increased anode life, extended operating time, and allows for longer continuous operation of the spray process without interruptions and deviations in coating quality.

[0043] The novel design can be used in thermal spray processes such as LPPS, VPS, PS-PVD, SPS and SPPS. The location of the different shroud gas inlets inside the anode, particularly upstream of the powder injection port, is advantageous and not used in conventional systems.

[0044] The present invention will not appear intuitive to those using conventional systems (with the common expectation that such configurations will cause the generated shroud gas to restrict the particle flow from the powder port to the hot gas or plasma, thereby reducing the efficiency of melting or vaporizing the injected feedstock. Second, with the injected shroud gas at room temperature, turbulence can be disadvantageously generated inside the nozzle or anode when the plasma jet is at temperatures up to 20,000K, which can deflect the particle flow from the axial direction.

[0045] However, experimental observations show that in the case of conventional anodes, coating accumulation begins with recondensation and / or liquid phase formation around the powder port. This is due to the fact that the feedstock as a powder has a certain size distribution and is injected into a mixture of cold gas and hot plasma gas (such as a plasma jet) of the carrier gas from the powder port. The cold walls of the anode, turbulence and strong temperature gradients at the powder port allow the coating material to accumulate around the powder port. However, when one places at least one inlet for supplying shroud gas near the powder port in the anode of the present invention (particularly upstream), this will limit this accumulation around the powder port on the anode wall by creating a gas film in which the feedstock cannot be deposited. The type and amount of the gas flow of the shroud gas and the precise position upstream can be controlled to allow limiting the negative effects of introducing cold gas upstream of the powder port as described previously, but at the same time will reduce the chance of feedstock accumulating upstream of the powder port. Additional configurations of shroud gas injection radially around and downstream of the powder port can be used to completely stop the formation of material accumulation during longer operation of the spray system.

[0046] Experimental data and numerical simulations also show that the use of shroud gas in the manner of the present invention can serve to direct and concentrate the powder particles toward the center of the hot gas or plasma jet and into the hottest zone, and the injected shroud gas thus forms a thin film of cold gas along the anode wall. In particular, injecting shroud gas upstream of the powder port can serve to prevent recondensation and / or liquid formation upstream of the powder port. This optimal configuration is due to the different flow rates present inside the nozzle from the injected shroud gas, the injected carrier gas, the powder particles, and the mixture of these colder gases together with the hotter gas flow generated by the plasma gas.

[0047] The gas inlet of the shield generating gas flow of the present invention can be arranged in the section of the anode where the powder injection is located. The powder material can be injected from one or several powder ports. The possible and optimal zone where the shield gas inlet should be located can be upstream of the powder port and downstream between the powder port toward the anode outlet. The total gas flow through one or several shield gas inlets can be between 50% and 150% of the total carrier gas flow injected through the powder port. The injected shield gas can be any inert gas, in particular argon or helium, but can also be a diatomic gas, such as nitrogen. The shield gas can be the same or different from the carrier gas used to inject the powder particles. The diameter or size of the shield gas inlet can be between 20% and 120% compared to the diameter or size of the powder port, in particular between 20% and 80%, preferably between 20% and 50%.

[0048] The powder injection port (and gas injector port 1) arranged in the nozzle / anode wall can be circular or non-circular, such as oval or elliptical (e.g., oblique elliptical), with the elongated end oriented in the upstream / downstream direction. In such cases, one can define it by an average diameter or opening size. Alternatively, one can define such an opening as having a diameter defined as the larger distance of the opening. Alternatively, one can define the opening by its open area, which can be used as its size. In addition to circular, oval or elliptical, the shape for the port can have other shapes, such as substantially rectangular, square, triangular, etc.

[0049] In all arrangements, there should be at least one shield gas inlet that can be located upstream of the powder port. There should be at least one upstream inlet located in an area with a radius of up to 3 times the diameter or size of the powder port around the powder port. Additional shield gas inlets can be placed upstream, in an area that is up to 3 times the diameter or size of the powder port in length relative to the powder port on the entire circumference. Downstream of the powder port, they can be located at any distance between the powder port and the anode outlet on the entire circumference. When one compares the minimum diameter and the maximum diameter, the diameter of the shield gas inlet can differ by up to 100%. The area in which at least one gas inlet is placed can be characterized as area A or the first area. The area in which additional inlets can be placed in different arrangements and undefined numbers can be characterized as area B or the second area. Typically, the diameter or size of the powder port in a vacuum system is between 0.5 and 5 mm, in particular between 1 and 3 mm. Practical examples have shown that a shield gas inlet diameter between 0.5 and 1.5 mm (preferably between 0.75 and 1 mm) can provide the best results. Similar to the powder injection ports, the injection of shroud gas may have different directions, axially and radially, relative to the main process gas flow, inducing some swirl effect to follow or counteract the flow and / or swirl of the main process gas flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The accompanying drawings are included to provide a further understanding of the present invention and are incorporated into and constitute a part of this specification. The accompanying drawings illustrate embodiments of the present invention and together with the description serve to explain the principles of the present invention. In the drawings:

[0051] Figure 1 A prior art VPS F4 spray gun is shown which employs internal injection of powder material inside the anode;

[0052] Figure 2 A prior art arrangement employing an internal shroud gas membrane is shown;

[0053] Figure 3 shows a cross section of a segment of an anode that can be used to practice the present invention, and shows various locations and area sizes;

[0054] Figure 4A and Figure 4B Shown is a cross section of a segment of an anode according to one non-limiting embodiment of the invention. Figure 4B The cross section of FIG. 4A is schematic and is taken orthogonally with respect to the cross section of FIG. 4A ;

[0055] Figure 5A and Figure 5B Shown is a cross section of a segment of an anode according to another non-limiting embodiment of the invention. Figure 5B The cross section of FIG. 5A is schematic and is taken orthogonally with respect to the cross section of FIG. 5A ;

[0056] Figure 6A and Figure 6B Shown is a cross section of a segment of an anode according to another non-limiting embodiment of the invention. Figure 6B The cross section of FIG. 6A is schematic and is taken orthogonally with respect to the cross section of FIG. 6A ;

[0057] Figure 7A and Figure 7B Shown is a cross section of a segment of an anode according to another non-limiting embodiment of the invention. Figure 7B The cross section of is schematic and is taken orthogonally with respect to the cross section of FIG. 7A ; and

[0058] Figure 8 An exemplary powder port is shown with an arcuate region defined by oblique elliptical powder injector openings of varying diameters. DETAILED DESCRIPTION

[0059] The following detailed description illustrates the principles of the present disclosure by way of example and not by way of limitation. This description will clearly enable one skilled in the art to make and use the present disclosure, and describes several embodiments, variations, modifications, substitutions, and uses of the present disclosure, including those currently considered to be the best modes for carrying out the present disclosure. It should be understood that the figures are diagrammatic and schematic representations of exemplary embodiments of the present disclosure, and do not limit the present disclosure, nor are they necessarily drawn to scale.

[0060] The novel features characteristic of the present disclosure, both as to its structure and method of operation, together with further objects and advantages thereof, will be understood from the following description considered in conjunction with the accompanying drawings, in which embodiments of the present disclosure are shown as examples. It is to be expressly understood, however, that the drawings are for purposes of illustration and description only and that they are not intended as a definition of the limits of the present disclosure.

[0061] In the following description, various embodiments of the present disclosure will be described with reference to the accompanying drawings. Detailed embodiments of the present disclosure are discussed herein as needed; however, it should be understood that the disclosed embodiments are merely examples of embodiments of the present disclosure that may be embodied in various and alternative forms. The drawings are not necessarily to scale, and some features may be enlarged or reduced to show details of particular components. Therefore, the specific structural and functional details disclosed herein are not to be considered restrictive, but merely as a representative basis for teaching those skilled in the art to adopt the present disclosure differently.

[0062] The details shown herein are presented as examples only and for the purpose of illustrative discussion of embodiments of the present disclosure, and are presented for the purpose of providing what is believed to be the most useful and easily understood description of the principles and concepts of the present disclosure. In this regard, no attempt is made to show the structural details of the present disclosure in more detail than is necessary for a basic understanding of the present disclosure, so that the description in conjunction with the figures makes it apparent to those skilled in the art how the form of the present disclosure may be embodied in implementation.

[0063] Unless the context clearly indicates otherwise, as used herein, the singular forms "a", "an", and "the" include plural referents. For example, reference to "a powder material" would also mean that, unless specifically excluded, a mixture of one or more powder materials may be present. As used herein, the indefinite article "a" indicates one as well as more than one, and does not necessarily limit the noun it refers to to the singular.

[0064] Unless otherwise indicated, all numbers used to express quantities in the specification and claims should be understood as being modified in all instances by the term "about". Therefore, unless indicated to the contrary, the numerical parameters set forth in the specification and claims are approximate values, which may vary depending on the desired properties sought to be obtained by the embodiments of the present disclosure. At the very least, and not to be construed as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should be interpreted in light of the number of significant digits and ordinary rounding conventions.

[0065] In addition, the enumeration of numerical ranges within this specification is considered to be the disclosure of all numerical values ​​and ranges within the range (unless otherwise explicitly indicated). For example, if the range is from about 1 to about 50, it is considered that the range includes, for example, 1, 7, 34, 46.1, 23.7, or any other value or range within the range.

[0066] As used herein, the terms "about" and "approximately" indicate that the amount or value in question may be the specified particular value or some other value in the vicinity thereof. Generally, the terms "about" and "approximately" indicating a value are intended to indicate a range within ±5% of that value. As an example, the phrase "about 100" indicates a range of 100±5, i.e., a range from 95 to 105. Generally, when the terms "about" and "approximately" are used, it is expected that similar results or effects according to the present disclosure can be obtained within a range of ±5% of the indicated value.

[0067] As used herein, the term "and / or" indicates that all or only one element of the group may be present. For example, "A and / or B" shall mean "only A, or only B, or both A and B". In the case of "only A", the term also covers the possibility of not having B, i.e., "only A, but not B".

[0068] The term "at least partially" is intended to mean that the following characteristics are achieved to some extent or completely.

[0069] The terms "substantially" and "substantially" are used to indicate that the following features, characteristics or parameters are fully (entirely) achieved or satisfied, or the expected results are not adversely affected to a large extent.

[0070] As used herein, the term "comprising" is intended to be non-exclusive and open-ended. Thus, for example, a composition comprising compound A may include other compounds in addition to A. However, the term "comprising" also encompasses the stricter meanings of "consisting essentially of" and "consisting of", such that, for example, a "composition comprising compound A" may also consist (essentially) of compound A.

[0071] Unless specifically stated to the contrary, the various embodiments disclosed herein may be used alone and in various combinations.

[0072] Now refer to Figure 3 To describe the present invention, Figure 3 A cross section of a section of an anode An is shown with a powder inlet or injection port P having a diameter "d" located in the wall W of the anode An. The port P may be arranged in a manner similar to Figure 1. The semicircular area marked with the letter A shows an area in which one or more shield gas inlets can be placed, which will be located near port P. Area A around the powder port P is located upstream of port P and is defined by a diameter of 3 times the diameter "d" of port P. The second larger area B may also include additional optional gas inlets and extends from an upstream position "x" to a downstream position "y". For example, in LPPS and PS-PVD type systems, the common powder port P diameter "d" is 3mm. Therefore, in such applications, at least one gas inlet (not shown) should be placed upstream of area A, which is defined by a semicircle with a diameter of 9mm. Upstream of the powder port P, additional gas inlets may be placed in the 9mm area A, and one or more additional gas inlets may also be placed upstream or downstream of the port P and outside the semicircular area A (i.e., in area B).

[0073] Figure 4A and Figure 4B Two orthogonal cross sections of an embodiment of an anode An are shown, the anode An comprising Figure 3 5 gas inlets I in region A of the powder port P are equidistant from and adjacent to the powder port P. In the case of such an arrangement, accumulation of carrier gas material around the powder port P is avoided. In the case of such an arrangement, the total shield gas through all gas inlet openings I may be different from the carrier gas flow through the anode An by 50% to 150%. Preferably, the gas flow is provided through the inlet I at a flow rate lower than 100% of the carrier gas flow. In addition, in the case of spraying conditions that are those used in LPPS (wherein the material is vaporized), one should note that excessive shield gas flow may lead to undesirable recondensation. The flow rate of the carrier gas and the shield gas may be 10% to 30% compared to the gas flow used to generate the plasma gas jet. The carrier gas flow may also be split among several powder port injectors or ports P and the covering gas inlet I. Typically, the total carrier gas flow may be between 5 and 60 NLPM (standard liters per minute). They may also be between 20 and 50 NLPM, and preferably between 25 and 40 NLPM. In another aspect, shroud airflow through inlet I may be set between 5 and 80 NLPM, typically between 20 and 75 NLPM, and preferably between 25 and 40 NLPM.

[0074] Figure 5A and Figure 5B Another embodiment of an anode A'n is shown, which has one or more powder injection ports P' and multiple gas inlets I'. In this case, the air inlet I' is located Figure 3 In the region A, at different distances from the powder port P'. Downstream of the port P', additional air inlets I' are arranged at another azimuth angle relative to the powder port P', some of which are located Figure 3 In region B. This embodiment is designed to generate a gas shield that follows the diffusion of the injected carrier gas. In addition to forming a protective gas shield between the anode wall and the material / plasma jet, this construction also causes the injected powder material to be deflected toward the anode axis into the zone of highest plasma temperature. Numerical simulations indicate that this will improve the heat transfer from the hot plasma jet to the powder particles, which brings higher efficiency relative to material deposition versus the amount of material injected. Especially in the case of PS-PVD spraying (where the powder material is transferred to the gas phase), a larger portion of the powder material will be vaporized compared to the classical anode design lacking a shield air inlet. As in the previous embodiment, the role of the inlet I' in region A is to prevent material from accumulating in the most critical area around the powder injection port P'. However, in this embodiment, the inlet I' located in region B is used to prevent material from accumulating in the anode wall.

[0075] Figure 6A and Figure 6B Another embodiment of an anode A''n is shown, which has one or more powder injection ports P' and a plurality of gas inlets I''. In this case, some of the air inlets I'' are located Figure 3 In the region A, at different distances from the powder port P''. Downstream of the port P'', additional air inlets I'' are arranged, and these are at another azimuth angle relative to the powder port P'', some of which are located at Figure 3 In region B. In addition, one or more air inlets I'' are located in region B between air inlets I'' arranged at a certain azimuth angle relative to the powder port P'', and these form a substantially circular group of gas inlets '' around the powder port P''. This embodiment is also designed to generate a gas shield that follows the diffusion of the injected carrier gas. In addition to forming a protective gas shield between the anode wall and the material / plasma jet, this construction also causes the injected powder material to be deflected toward the anode axis into the zone of highest plasma temperature. It is believed that this arrangement can improve the heat transfer from the hot plasma jet to the powder particles, which can bring higher efficiency relative to material deposition versus the amount of material injected. Especially in the case of PS-PVD spraying (where the powder material is transferred to the gas phase), a larger portion of the powder material will be vaporized compared to the classical anode design lacking a shield air inlet. As with the previous embodiment, the inlet I'' in region A is used to prevent material from accumulating in the most critical area around the powder injection port P''. However, in this embodiment, the inlet I' located in the region B is believed to function to prevent accumulation of material in the anode wall.

[0076] Figure 7A and Figure 7BAnother embodiment of an anode A'''n having one or more powder injection ports P''' and a single arc-shaped gas inlet I''' is shown. In this case, the arc-shaped air inlet I''' is located Figure 3 In region A, where the end portion is located at a different distance from the powder port P'''. Downstream of the port P''', an additional gas inlet I''' (not shown in Figure 7) can be arranged in a manner similar to the previous embodiment. This embodiment can also be designed to generate a gas shield that follows the diffusion of the injected carrier gas. In addition to forming a protective gas shield between the anode wall and the material / plasma jet, the construction also causes the injected powder material to be deflected toward the anode axis to the zone of the highest plasma temperature. It is believed that this arrangement can improve the heat transfer from the hot plasma jet to the powder particles, which can bring higher efficiency relative to the amount of material deposited versus injected. Especially in the case of PS-PVD spraying (where the powder material is transferred to the gas phase), a larger portion of the powder material will be vaporized compared to the classical anode design lacking a shield air inlet. As in the previous embodiment, the elongated arc inlet I''' in region A is used to prevent material from accumulating in the most critical area around the powder injection port P'''.

[0077] The powder injection ports P, P', P" or P'" and the gas injector ports or inlets I, I', I" and I'" may be circular or non-circular, such as oval or elliptical (eg, oblique elliptical), with the elongated ends oriented in the upstream / downstream direction. Figure 8 An example of an oblique oval powder port P is shown. In such a case, the port P may be defined by an average diameter or by the size of the opening. Alternatively, such an opening may be defined as having a diameter defined as the greater distance of the opening (based on the use of the major axis), i.e., Figure 8 When defining area A, vertical arrow R1 can be used to determine area A (indicating Figure 8 The area A (indicated by the larger semicircle in the figure) can be determined by 3 times the distance D1, or the horizontal arrow R2 (based on the use of the minor axis) can be used to determine the area A (indicated by the larger semicircle in the figure). Figure 8 The area covered by the smaller semicircle in the middle is 3 times the distance D2. In the case of such non-circular openings or ports P, the present invention contemplates the use of either option. Alternatively, the opening or port P can be defined by its open area, and this can be used as its size. In addition to circular, oval or elliptical shapes, the shape for the port can have other shapes, such as generally rectangular, square, triangular, etc.

[0078] The air inlets I, I', I'' and I''' of the shield generating air flow of the present invention can be arranged in the section of the anodes An, A'n, A''n and A'''n where the powder injection ports P, P', P'' and P''' are located. Powder material can be injected from one or several powder ports. The possible and optimal zone where the shield gas inlet should be located can be upstream of the powder port and downstream between the powder port and the outlet toward the anode. The total airflow through one or several shield gas inlets can be between 50% and 150% of the total carrier gas flow injected through the powder port. The injected shield gas can be any inert gas, in particular argon or helium, but can also be a diatomic gas, such as nitrogen. The shield gas can be the same as or different from the carrier gas used to inject the powder particles. The diameter of each shroud gas inlet I, I', I'' and I''' may be between 20% and 120%, particularly between 20% and 80%, preferably between 20% and 50%, compared to the diameter of the powder ports P, P', P'' and P'''.

[0079] In all arrangements, there should be at least one shroud gas inlet that may be located upstream of the powder port. There should be at least one upstream inlet located in an area with a radius of up to 3 times the diameter or dimension of the powder port around the powder port P, P', P'' or P'''. Additional shroud gas inlets I, I', I'' or I''' may be placed upstream in an area of ​​up to 3 times the diameter or length dimension of the powder port relative to the powder port over the entire circumference. Downstream of the powder port, they may be located at any distance between the powder port P, P', P'' or P''' and the anode outlet over the entire circumference. The diameter or dimension of the shroud gas inlet I, I', I'' or I''' may differ by up to 100% when comparing the minimum diameter and the maximum diameter. The area in which at least one gas inlet is placed may be characterized as area A or the first area (see Figure 3 The area in which the additional inlets can be placed in different arrangements and in an undefined number can be characterized as area B or second area (see Figure 3 ). Typically, the powder port diameter of the powder port in a vacuum type system is between 0.5 and 5 mm, in particular between 1 and 3 mm. Practical examples have demonstrated that a diameter of the shroud gas inlet I, I', I'' or I''' of the gas inlet I of between 0.5 and 1.5 mm, preferably between 0.75 and 1 mm, provides the best results. Similar to the powder injection port P, P', P'' or P''', the injection of the shroud gas via the inlet I, I', I'' or I''' may have different directions axially and radially relative to the main process gas flow, inducing a certain swirl effect to follow or counteract the flow and / or swirl of the main process gas flow.

[0080] Furthermore, at least because the invention is disclosed herein in a manner that enables one to make and use the invention (such as by way of disclosure of specific exemplary embodiments for simplicity or efficiency), the invention may be practiced without any additional elements or additional structures not specifically disclosed herein.

[0081] Note that the foregoing examples are provided for illustrative purposes only and are in no way to be considered as limiting the present invention. Although the present invention is described with reference to exemplary embodiments, it is to be understood that the words used herein are words of description and illustration, not words of limitation. Changes may be made within the scope of the appended claims as currently stated and amended without departing from the scope and spirit of the present invention in its aspects. Although the present invention is described herein with reference to specific devices, materials, and embodiments, the present invention is not intended to be limited to the details disclosed herein; on the contrary, the present invention extends to all functionally equivalent structures, methods, and uses, such as those within the scope of the appended claims.

Claims

1. A plasma nozzle, comprising: a nozzle body arranged to engage with a thermal spray gun; The nozzle body comprises: an axial throughbore having an upstream input orifice and a downstream nozzle outlet; at least one material injector opening in a wall of the nozzle body positioned between the upstream input orifice and the nozzle outlet, the at least one material injector configured to introduce feedstock into the gas flow through the axial throughbore; and At least one gas injector opening in the wall of the nozzle body is configured to introduce a shroud gas flow into the axial through hole perpendicular to the axis of the nozzle body and is located at a position upstream of the at least one material injector opening, wherein the at least one gas injector opening is arranged in a semicircular or arc-shaped area defined by 3 times the diameter or size of the at least one material injector opening, and the radius of the area extends from the central axis of the at least one material injector opening, wherein the at least one gas injector opening is a first opening, and the at least one material injector opening is a second opening.

2. The plasma nozzle according to claim 1, characterized in that The at least one gas injector opening is smaller in diameter or size than the at least one material injector opening.

3. The plasma nozzle according to claim 1, characterized in that The first opening includes a plurality of openings spaced apart by the same amount from a central axis of the second opening.

4. The plasma nozzle according to claim 1, characterized in that The first opening includes a plurality of openings spaced apart from a central axis of the second opening by different amounts.

5. The plasma nozzle according to claim 1, characterized in that The second opening includes a plurality of openings.

6. The plasma nozzle according to claim 1, characterized in that The plasma nozzle also includes at least one downstream gas injector positioned downstream of the at least one material injector.

7. The plasma nozzle according to claim 6, characterized in that The at least one downstream gas injector includes a plurality of downstream gas injectors positioned at an azimuth angle relative to a central axis of the axial throughbore.

8. The plasma nozzle according to claim 1, characterized in that The nozzle body is an anode.

9. The plasma nozzle according to claim 1, characterized in that The nozzle body is the anode of the thermal spray gun.

10. The plasma nozzle according to claim 1, characterized in that The at least one gas injector is a circular opening in the inner wall of the nozzle body, and the at least one material injector is a circular opening in the inner wall of the nozzle body.

11. The plasma nozzle according to claim 1, characterized in that The at least one gas injector is a non-circular opening in the inner wall of the nozzle body and the at least one material injector is a circular opening in the inner wall of the nozzle body.

12. The plasma nozzle according to claim 1, characterized in that The at least one gas injector is a circular opening in the inner wall of the nozzle body and the at least one material injector is a non-circular opening in the inner wall of the nozzle body.

13. The plasma nozzle according to claim 1, characterized in that The at least one gas injector is a non-circular opening in the inner wall of the nozzle body, and the at least one material injector is a non-circular opening in the inner wall of the nozzle body.

14. A thermal spray gun comprising the plasma nozzle according to claim 1.

15. A thermal spray gun plasma nozzle comprising: an anode, the anode comprising: an axial throughbore having an upstream input orifice and a downstream nozzle outlet; at least one material ejector opening in a wall of the nozzle body positioned between the upstream input orifice and the nozzle outlet, the at least one material ejector opening configured to introduce feedstock into the gas flow through the axial throughbore; and at least one gas injector opening in the wall of the nozzle body configured to direct a shroud gas flow into the axial throughbore perpendicular to the axis of the nozzle body and located at a position upstream of the at least one material injector opening, wherein the at least one gas injector opening is smaller in diameter or size than the at least one material injector opening, Wherein the at least one gas injector opening is arranged in a semicircular or arcuate area defined by 3 times the diameter or size of the at least one material injector opening, and the radius of the area extends from the central axis of the at least one material injector opening.

16. The thermal spray gun plasma nozzle according to claim 15, characterized in that The at least one gas injector opening includes a plurality of openings spaced from a central axis of the at least one material injector opening.

17. The thermal spray gun plasma nozzle according to claim 15, characterized in that The at least one gas injector opening includes a plurality of openings spaced at different amounts from a central axis of the at least one material injector opening.

18. A method of using a plasma nozzle according to any one of claims 1 to 13 or a thermal spray gun plasma nozzle according to any one of claims 15 to 17, the method comprising: When the powder is introduced via the at least one material injector opening using a carrier gas flow, the inert gas is introduced through the at least one gas injector opening at a total gas flow of between 50% and 150% of the total carrier gas flow, the at least one gas injector opening being located upstream of the at least one material injector opening and within a semicircular or arc-shaped area defined by 3 times the diameter or size of the at least one material injector opening, and the radius of the area extends from the central axis of the at least one material injector opening.

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