Method for producing tungsten carbide composite powder by magnetron sputtering and coating applications thereof

Abstract

The application provides a method for preparing tungsten carbide composite powder by magnetron sputtering and coating application thereof, and relates to the technical field of hard powder preparation, which comprises the following steps: adding tungsten carbide powder into a vacuum chamber of a magnetron sputtering device, and making the tungsten carbide powder in a continuous tumbling state under an inert atmosphere; performing argon ion etching treatment on the tumbling tungsten carbide powder; and controlling the sputtering power of a CrY alloy target and a Co target, so that the composition of the CrY / Co coating layer formed by deposition presents a continuous gradient change along the radial direction, and the content of the CrY alloy gradually decreases from the inner layer to the outer layer, and the content of Co gradually increases from the inner layer to the outer layer. The CrY / Co coating layer prepared by the application has a smooth composition transition and low interface stress, the CrY realizes synergistic modification, the coating density and interface bonding performance can be significantly improved, and the mechanical properties and corrosion resistance and wear resistance of the material are synergistically optimized.

Description

Technical Field

[0001] This invention relates to the field of hard powder preparation technology, specifically to a method for preparing tungsten carbide composite powder by magnetron sputtering and its coating application. Background Technology

[0002] WC-Co cemented carbide coatings, due to their combination of high hardness and good toughness, are widely used for surface protection of components in aerospace, marine engineering, and mining machinery. Industrially, HVOF (High-Velocity Volcanic Flame) spraying is commonly used to prepare WC-Co coatings, where WC particles act as hard reinforcement, and metallic cobalt acts as a binder phase filling the gaps between the hard phases to achieve overall coating formation. However, under high-temperature spraying and complex corrosion and wear conditions, coatings prepared from traditional unmodified WC powder generally suffer from defects such as weak interfacial bonding, easy pull-out and detachment of WC particles, high coating porosity, and poor corrosion resistance, severely shortening the service life of components. Therefore, controllable surface coating modification of WC powder and optimization of the elemental distribution and interfacial structure of the coating layer have become important research directions for improving the overall performance of WC-Co coatings.

[0003] Current surface coating modification technology for WC powder mainly relies on liquid-phase chemical coating. However, liquid-phase chemical coating requires large amounts of chemical reagents, easily generating waste liquid pollution. Furthermore, the coating layer often exhibits a multi-layered, abrupt structure with significant interlayer interface differences, leading to concentrated interfacial thermal stress during service and a high susceptibility to interlayer cracking and detachment. Additionally, liquid-phase coating suffers from uneven powder coating, poor batch stability, low process repeatability, and difficulty in industrial-scale mass production. Some technologies introduce yttrium and chromium for modification, but these are mostly oxide doping or uniform doping of a single element, resulting in limited elemental function and difficulty in simultaneously achieving interfacial bonding strength and material corrosion resistance. Moreover, excessive yttrium can easily precipitate brittle phases, thus deteriorating the coating's mechanical properties. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing tungsten carbide composite powder by magnetron sputtering and its coating application, aiming to solve at least one technical problem in the background art.

[0005] A first aspect of the present invention is to provide a method for preparing tungsten carbide composite powder by magnetron sputtering, the method comprising: Tungsten carbide powder is added to the vacuum chamber of a magnetron sputtering equipment and kept in a state of continuous agitation under an inert atmosphere. Argon ion etching is performed on the tungsten carbide powder that is being turned over. A CrY / Co coating layer was deposited on the surface of etched tungsten carbide powder particles by dual-target co-sputtering using a CrY alloy target and a Co target. In the dual-target co-sputtering process, by controlling the sputtering power of the CrY alloy target and the Co target, the composition of the deposited CrY / Co coating layer changes continuously in the radial direction. In the CrY / Co coating layer, the content of CrY alloy gradually decreases from the inner layer to the outer layer, and the content of Co gradually increases from the inner layer to the outer layer.

[0006] According to one aspect of the above technical solution, the average particle size of the tungsten carbide powder is 5μm-30μm, the inert atmosphere is argon, and the working pressure is 0.2Pa-1.0Pa.

[0007] According to one aspect of the above technical solution, the parameters of the argon ion etching process are: bias voltage of -200V to -50V, ion energy of 300eV to 800eV, and etching time of 10min to 30min.

[0008] According to one aspect of the above technical solution, the Y content in the CrY alloy target is 5 at%-15 at%.

[0009] According to one aspect of the above technical solution, the dual-target co-sputtering process includes multiple consecutive deposition stages, the number of which is 5-30; Within each deposition stage, the sputtering power of the CrY alloy target and the Co target remains constant. Between adjacent deposition stages, the sputtering power of the CrY alloy target and the Co target changes stepwise according to the first preset gradient power and the second preset gradient power, respectively, and the first preset gradient power and the second preset gradient power are both no greater than 100W.

[0010] According to one aspect of the above technical solution, the deposition power of the CrY alloy target is 30W-300W, the deposition power of the Co target is 0W-300W, and during the sputtering process, the working gas pressure is 0.2Pa-1.0Pa, the cavity temperature is 30℃-200℃, and the sputtering time is 90min-150min.

[0011] According to one aspect of the above technical solution, in the CrY / Co coating layer, the content of Co gradually increases from 0at%-20at% to 80at%-100at% in the radial direction from the inner layer to the outer layer, while the content of CrY alloy gradually decreases from 80at%-100at% to 0at%-20at%.

[0012] According to one aspect of the above technical solution, the thickness of the CrY / Co coating layer is 1μm-5μm, and the thickness of each deposition stage is 0.1μm-0.6μm.

[0013] A second aspect of the present invention is to provide a tungsten carbide composite powder, which is prepared by the above-described method for preparing tungsten carbide composite powder by magnetron sputtering.

[0014] A third aspect of the present invention is to provide an application of the tungsten carbide composite powder as described above in a coating, wherein the tungsten carbide composite powder is mixed with cobalt powder, nickel powder or cobalt-nickel alloy powder, and then sprayed and granulated or mechanically fused to obtain a thermal spray powder with a particle size of 10μm-60μm, which is then deposited on the surface of a metal substrate by supersonic flame spraying, plasma spraying or cold spraying to form a coating.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. By adopting stepped power control in multiple deposition stages, the composition of the coating layer is radially smooth and continuous, without obvious abrupt interface changes. This effectively releases residual thermal stress in the coating, avoids interface cracking and peeling, and ultimately achieves a comprehensive improvement in coating hardness, wear resistance, corrosion resistance and density, making it suitable for service under complex and harsh working conditions.

[0016] 2. Optimization of the Cr and Y ratio achieves synergistic modification, which not only strengthens the interfacial bonding between the CrY / Co coating layer and the tungsten carbide matrix, but also avoids the precipitation of brittle phases. At the same time, the inner layer of the CrY / Co coating layer is enriched with CrY to strengthen the interfacial bonding, while the outer layer is enriched with Co to improve compatibility with the binder phase, improve wetting effect, and enhance the coating density and resistance to particle peeling. The CrY / Co gradient solves the contradiction between interfacial bonding (requiring strong chemical bonds between CrY and WC) and wetting (requiring compatibility between Co and the binder phase) of the WC-Co coating in the HVOF spraying process.

[0017] 3. This invention uses a vacuum magnetron sputtering dry method for preparation, which produces no chemical waste liquid, is green and environmentally friendly, and can effectively inhibit element oxidation; the process power control is simple, the parameters are highly adjustable, and the batch stability is good. Attached Figure Description

[0018] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a SEM image of the tungsten carbide composite powder prepared in Example 1 of the present invention; Figure 2 This is a SEM-EDS line scan image of the tungsten carbide composite powder prepared in Example 1 of the present invention; Figure 3 This is a SEM image of the coating prepared in Example 1 of the present invention. Detailed Implementation

[0019] To make the objectives, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. Several embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0020] This invention provides a method for preparing tungsten carbide composite powder by magnetron sputtering, the method comprising: steps S1-S3.

[0021] Step S1: Add tungsten carbide powder into the vacuum chamber of the magnetron sputtering equipment and keep the tungsten carbide powder in a state of continuous tumbling under an inert atmosphere. The tungsten carbide powder has an average particle size of 5μm-30μm, the inert atmosphere is argon, and the working pressure is 0.2Pa-1.0Pa, forming a high vacuum environment to reduce the contamination of the subsequent sputtering process by residual gas, especially to avoid the reaction of active γ with oxygen and water vapor.

[0022] The rotation speed of the vacuum chamber is controlled at 30rpm-60rpm to keep the tungsten carbide powder in the vacuum chamber in a continuous and uniform state of continuous tumbling throughout the entire process, and the powder tumbling is maintained throughout the subsequent ion etching and sputtering deposition processes.

[0023] Step S2: Perform argon ion etching on the tungsten carbide powder that is being turned over; The parameters for the argon ion etching process are: bias voltage of -50V to 200V, ion energy of 300eV to 800eV, and etching time of 10min to 30min. High-energy argon ions bombard the surface of WC particles, removing the surface oxide layer and adsorbed contaminants through physical sputtering. Simultaneously, surface lattice defects and dangling bonds are generated, increasing surface energy and improving the bonding force between subsequent sputtered atoms and the substrate. The activated surface is more conducive to the nucleation and growth of Cr, Y, and Co atoms, avoiding peeling or poor adhesion of the coating layer caused by contaminants.

[0024] Step S3 involves co-sputtering with a CrY alloy target and a Co target to deposit a CrY / Co coating layer on the surface of etched tungsten carbide powder particles. In the dual-target co-sputtering process, by controlling the sputtering power of the CrY alloy target and the Co target, the composition of the deposited CrY / Co coating layer changes continuously in the radial direction. In the CrY / Co coating layer, the content of CrY alloy gradually decreases from the inner layer to the outer layer, and the content of Co gradually increases from the inner layer to the outer layer. The Y content in the CrY alloy target is 5 at%-15 at%.

[0025] Specifically, the dual-target co-sputtering process includes multiple consecutive deposition stages, the number of which is 5-30; Within each deposition stage, the sputtering power of the CrY alloy target and the Co target remains constant. Between adjacent deposition stages, the sputtering power of the CrY alloy target and the Co target changes stepwise according to the first preset gradient power and the second preset gradient power, respectively, and the first preset gradient power and the second preset gradient power are both no greater than 100W.

[0026] Specifically, the deposition power of the CrY alloy target is 30W-300W, the deposition power of the Co target is 0W-300W, the working gas pressure is 0.2Pa-1.0Pa, the cavity temperature is 30℃-200℃, and the sputtering time is 90min-150min.

[0027] In the CrY / Co coating layer, the Co content gradually increases from 0at%-20at% to 80at%-100at% radially from the inner layer to the outer layer, while the CrY alloy content gradually decreases from 80at%-100at% to 0at%-20at%.

[0028] Furthermore, the thickness of the CrY / Co coating layer is 1μm-5μm, and the thickness of each deposition stage is 0.1μm-0.6μm.

[0029] The step power control during the deposition stage causes the composition of the CrY / Co coating layer deposited on the surface of tungsten carbide powder particles to change stepwise with radial position (from inner layer to outer layer), with an approximately continuous gradient. This results in a smooth composition change without significant abrupt interfaces, unlike the obvious abrupt interfaces of traditional multilayer coatings. This significantly reduces the interfacial thermal stress generated during the high-temperature spraying process and structurally avoids interface cracking and interlayer delamination failure.

[0030] Furthermore, the inner layer near the tungsten carbide powder has a high content of CrY phase, and Cr and Y form strong chemical bonds with the tungsten carbide powder, which significantly enhances the interfacial bonding strength; the outer layer is rich in Co, which has the same chemical composition as the Co binder phase in the WC-Co coating. During the spraying process, it can promote the wetting of molten Co on the tungsten carbide powder particles and improve the density of the coating.

[0031] Accordingly, the present invention also provides a tungsten carbide composite powder, which is prepared by the above-described method for preparing tungsten carbide composite powder by magnetron sputtering.

[0032] In addition, the present invention also provides an application of the tungsten carbide composite powder as described above in a coating, wherein the tungsten carbide composite powder is mixed with cobalt powder, nickel powder or cobalt-nickel alloy powder, and then sprayed and granulated or mechanically fused to obtain a thermal spray powder with a particle size of 10μm-60μm, which is then deposited on the surface of a metal substrate by supersonic flame spraying, plasma spraying or cold spraying to form a coating.

[0033] The technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0034] Example 1 The present invention provides a method for preparing tungsten carbide composite powder by magnetron sputtering, the method comprising: steps S1-S3.

[0035] Step S1: Take 50g of tungsten carbide powder with an average particle size of 10μm and add it to the vacuum chamber of the magnetron sputtering equipment. The powder filling ratio is 25% of the powder container volume. Use DC magnetron sputtering mode and evacuate to a background vacuum of 5×10⁻⁶. - 4 Pa, introduce argon gas at a flow rate of 40 sccm, adjust the working pressure to 0.6 Pa, set the target distance to 80 mm, and rotate the vacuum chamber at a speed of 40 rpm.

[0036] Step S2: Turn on the argon ion source, set the argon ion energy to 500 eV, the substrate bias voltage to -120 V, and the etching time to 20 min to complete the argon ion etching process.

[0037] Step S3: Co-sputtering of the CrY target (Y atom percentage of 10 at%) and the Co target is initiated using a DC power supply. The total deposition time is set to 120 min, which is then divided into 10 deposition stages, each lasting 12 min. The power for each deposition stage is set as follows: Inner layer - first deposition stage: CrY alloy target 300W, Co target 0W; Second deposition stage: CrY alloy target 270W, Co target 30W; Third deposition stage: CrY alloy target 240W, Co target 60W; Fourth deposition stage: CrY alloy target 210W, Co target 90W; Fifth deposition stage: CrY alloy target 180W, Co target 120W; 6th deposition stage: CrY alloy target 150W, Co target 150W; 7th deposition stage: CrY alloy target 120W, Co target 180W; 8th deposition stage: CrY alloy target 90W, Co target 210W; 9th deposition stage: CrY alloy target 60W, Co target 240W; Outer layer - 10th deposition stage: CrY alloy target 30W, Co target 270W.

[0038] During deposition, the working gas pressure was maintained at 0.6 Pa, and the substrate temperature was approximately 80 °C. The Y content in the CrY alloy target was 10 at%.

[0039] From the inner layer to the outer layer, the Co content gradually increases from 0 at% to approximately 97 at%, while the CrY alloy content gradually decreases from approximately 97 at% to approximately 3 at%. Figure 2 As shown, it exhibits an approximately continuous gradient distribution.

[0040] The compositional variation between adjacent depositional stages is approximately 10 at%, with each stage corresponding to a thickness of approximately 0.2 μm. For example... Figure 1 As shown, the total thickness of the CrY / Co coating is approximately 2 μm; The above-mentioned tungsten carbide composite powder was mixed with 8 wt% Co powder, and spray-granulated to obtain a thermal spray powder with a particle size of 10 μm-60 μm. The coating was then prepared by HVOF supersonic flame spraying. (See...) Figure 3 .

[0041] Example 2 The difference between Embodiment 2 and Embodiment 1 is that the number of deposition stages is 20, the power of the CrY alloy target is changed from 300W to 30W, the power of the Co target is changed from 0W to 270W, and the other steps remain unchanged.

[0042] Example 3 The difference between Embodiment 3 and Embodiment 1 is that the number of deposition stages is 5, the power of the CrY alloy target is changed from 300W to 30W, the power of the Co target is changed from 0W to 270W, and the other steps remain unchanged.

[0043] Example 4 The difference between Embodiment 4 and Embodiment 1 is that the coating thickness is 5 μm, which is achieved by extending the sputtering time of each deposition stage from 12 min to 30 min (total deposition time 300 min). The number of deposition stages remains 10, the power settings of each stage are the same as in Embodiment 1, and other steps remain unchanged.

[0044] Example 5 The difference between Example 5 and Example 1 is that the Y content in the CrY alloy target is 5 at%, while the other steps remain unchanged.

[0045] Example 6 The difference between Example 6 and Example 1 is that the Y content in the CrY alloy target is 15 at%, while the other steps remain unchanged.

[0046] Comparative Example 1 The difference between Comparative Example 1 and Example 1 of the present invention is that the Cr target is replaced with a CrY alloy target, Y is not added, and the other steps remain unchanged.

[0047] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the Y target is replaced with a CrY alloy target, Cr is not added, and the other steps remain unchanged.

[0048] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the power of the CrY alloy target is 150W, the power of the Co target is 150W, the power remains constant, the total thickness is about 2μm, and other steps remain unchanged.

[0049] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the number of deposition stages is 2, the power of the CrY alloy target is changed from 300W to 30W, the power of the Co target is changed from 0W to 270W, and the other steps remain unchanged.

[0050] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that only a Co target is used for sputtering (coating a pure Co layer), and no CrY alloy target is used, while the other steps remain unchanged.

[0051] Comparative Example 6 The difference between Comparative Example 6 and Example 1 of this invention is that: The power of the CrY alloy target was changed from 300W to 30W, and the power of the Co target was changed from 0W to 270W, with the power continuously varying. The total thickness was about 2μm, while other steps remained unchanged.

[0052] Comparative Example 7 The difference between Comparative Example 6 and Example 1 of this invention is that: The power of the CrY alloy target is 150W, the power of the Co target is 150W, and the power remains constant. The multilayer structure formed by the alternating sputtering of the two targets has a total thickness of about 2μm, and other steps remain unchanged.

[0053] Comparative Example 8 The difference between Comparative Example 8 and Example 1 of this invention is that: Argon ion etching is not performed; all other steps remain unchanged.

[0054] Comparative Example 9 The difference between Comparative Example 9 and Example 1 of this invention is that: The Y content in the CrY alloy target is 1 at%, while other steps remain unchanged.

[0055] Please refer to Table 1 below, which shows the parameters corresponding to the above embodiments and comparative examples of the present invention. The powders corresponding to the above embodiments and comparative examples were mixed with 8 wt% Co powder (based on the mass of tungsten carbide composite powder), and spray-granulated to obtain thermal spray powder with a particle size of 10 μm-60 μm. A coating was prepared by HVOF supersonic flame spraying, and then performance tests were performed. Hardness was tested using the Vickers microhardness test, and wear rate was tested using the ball-and-disc wear test method. Corrosion current density was tested using a three-electrode system + potentiodynamic polarization method + Tafel extrapolation method, and porosity was measured using SEM cross-sectional image analysis, 5000x magnification, and the average value of 5 fields of view. See Table 1.

[0056] Table 1:

[0057] As shown in Table 1, this application significantly improves the coating density and interfacial bonding performance through the synergistic effect of argon ion etching pretreatment and CrY / Co gradient coating. After omitting the argon ion etching treatment, the porosity of the coating increases significantly and the hardness decreases significantly, proving that the etching step is the key to obtaining a high-quality coating layer.

[0058] The Y content in the CrY alloy target used in this application (5 at%-15 at%) is much higher than the Y content (1 at%) in proportion 9. This high Y content has a synergistic modification effect with Cr. When the Y content is increased from 1 at% to more than 5 at%, the corrosion resistance of the coating shows a significant leap, while the performance remains stable when the Y content is further increased (to 15 at%).

[0059] Meanwhile, when the number of deposition stages increased from 5 to 10, the porosity and wear rate of the coating were significantly improved; when the number of stages was further increased to 20, the performance was further optimized.

[0060] Furthermore, the porosity and wear rate of Comparative Example 7 (abruptly multilayered structure formed by alternating dual-target sputtering) were significantly worse than those of Example 1, demonstrating that a continuous gradient structure with smooth radial transition of components can effectively reduce interfacial thermal stress and defects. Comparative Example 6 (continuously varying power) also exhibited worse porosity and wear rate than Example 1, proving that the multi-stage stepped power (constant at each stage, gradually varying) of this application is more conducive to ensuring the consistency of sputtering flux received by each particle under powder tumbling conditions, thereby obtaining a denser coating.

[0061] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0062] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for preparing tungsten carbide composite powder by magnetron sputtering, characterized in that, The method includes: Tungsten carbide powder is added to the vacuum chamber of a magnetron sputtering equipment and kept in a state of continuous agitation under an inert atmosphere. Argon ion etching is performed on the tungsten carbide powder that is being turned over. A CrY / Co coating layer was deposited on the surface of etched tungsten carbide powder particles by dual-target co-sputtering using a CrY alloy target and a Co target. In the dual-target co-sputtering process, by controlling the sputtering power of the CrY alloy target and the Co target, the composition of the deposited CrY / Co coating layer changes in a stepwise manner along the radial direction. In the CrY / Co coating layer, the content of CrY alloy gradually decreases from the inner layer to the outer layer, and the content of Co gradually increases from the inner layer to the outer layer. The Y content in the CrY alloy target is 5 at%-15 at%. The dual-target co-sputtering process includes multiple consecutive deposition stages, and the number of deposition stages is 5-30. Within each deposition stage, the sputtering power of the CrY alloy target and the Co target remains constant. Between adjacent deposition stages, the sputtering power of the CrY alloy target and the Co target changes stepwise according to the first preset gradient power and the second preset gradient power, respectively, and the first preset gradient power and the second preset gradient power are both no greater than 100W.

2. The method for preparing tungsten carbide composite powder by magnetron sputtering according to claim 1, characterized in that, The tungsten carbide powder has an average particle size of 5μm-30μm, the inert atmosphere is argon, and the working pressure is 0.2Pa-1.0Pa.

3. The method for preparing tungsten carbide composite powder by magnetron sputtering according to claim 1, characterized in that, The parameters for the argon ion etching process are: bias voltage of -200V to -50V, ion energy of 300eV to 800eV, and etching time of 10min to 30min.

4. The method for preparing tungsten carbide composite powder by magnetron sputtering according to claim 1, characterized in that, The deposition power of the CrY alloy target is 30W-300W, and the deposition power of the Co target is 0W-300W. During the sputtering process, the working gas pressure is 0.2Pa-1.0Pa, the cavity temperature is 30℃-200℃, and the sputtering time is 90min-150min.

5. The method for preparing tungsten carbide composite powder by magnetron sputtering according to claim 1, characterized in that, In the CrY / Co coating layer, the Co content gradually increases from 0at%-20at% to 80at%-100at% radially from the inner layer to the outer layer, while the CrY alloy content gradually decreases from 80at%-100at% to 0at%-20at%.

6. The method for preparing tungsten carbide composite powder by magnetron sputtering according to claim 1, characterized in that, The thickness of the CrY / Co coating is 1μm-5μm, and the thickness of each deposition stage is 0.1μm-0.6μm.

7. A tungsten carbide composite powder, characterized in that, The tungsten carbide composite powder is prepared by the method for preparing tungsten carbide composite powder by magnetron sputtering according to any one of claims 1-6.

8. The application of the tungsten carbide composite powder as described in claim 7 in a coating, characterized in that, The tungsten carbide composite powder is mixed with cobalt powder, nickel powder or cobalt-nickel alloy powder, and then sprayed and granulated or mechanically fused to obtain a thermal spray powder with a particle size of 10μm-60μm. The powder is then deposited on the surface of a metal substrate to form a coating by supersonic flame spraying, plasma spraying or cold spraying.

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