Method for preparing coating by ultrasonic-assisted jet plasma

Abstract

The invention discloses an ultrasonic-assisted jet machining method and a workpiece. The ultrasonic-assisted jet machining method comprises the steps that a jet device and a workpiece to be machined are oppositely arranged, a jet outlet faces the surface of the workpiece, and the workpiece and the jet device are connected with a plasma power source; electrolyte is guided into the cavity, the jet device is controlled to conduct ultrasonic vibration, the electrolyte is made to generate cavitation bubbles, and mixed fluid is obtained; and the voltage and duty ratio of the plasma power supply are adjusted, so that the mixed fluid generates plasma through the jet flow outlet, and a plasma oxide layer is generated on the surface of the workpiece. The plasma intensity is improved through ultrasonic cavitation, the thickness of an oxidation layer is increased, a compact and uniform ceramic film layer can be generated on the metal surface through plasma oxidation, the wear resistance and the corrosion resistance of the ceramic film layer are remarkably superior to those of an anodic oxidation or hard anodic oxidation film, and the service life of a workpiece can be remarkably prolonged.

Description

Technical Field

[0001] The present application relates to the technical field of microstructure processing, and in particular to a method for preparing coatings using ultrasonic-assisted jet plasma. Background Art

[0002] Micro-arc oxidation technology (MAO), also known as plasma electrolytic oxidation (PEO), is a surface treatment technology developed from the anodizing process. For the base metal material of the workpiece, on the basis of ordinary anodizing, the inter-electrode voltage is increased from the Faraday zone of ordinary anodizing to the high-voltage discharge zone, and the arc discharge is used to enhance and activate the reaction on the anode to produce micro-arc plasma spark discharge. Relying on the instantaneous high temperature and high pressure, a ceramic film layer mainly composed of base metal oxide is grown in situ to protect the substrate. However, the traditional micro-arc oxidation process is to immerse the workpiece in the working fluid. The presence of the electrolytic cell not only limits the size of the workpiece, but also makes it difficult to carry out on-site protection and repair of some parts that have been installed and positioned. In addition, the plasma intensity generated by this method is difficult to guarantee, and the growth rate of the metal oxide ceramic film layer needs to be improved. Summary of the invention

[0003] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes a simple and convenient method for preparing a coating by ultrasonic-assisted jet plasma, which has high plasma intensity and fast growth rate of a metal oxide ceramic film layer.

[0004] In a first aspect of the present application, there is provided a method for preparing a coating by ultrasonic-assisted jet plasma, comprising the following steps:

[0005] The ejector is arranged opposite to the workpiece to be processed, the ejector has a shell, a chamber for containing electrolyte is formed in the shell, a jet outlet is arranged at one end of the chamber, the jet outlet is directed toward the surface of the workpiece, and the workpiece and the ejector are respectively connected to a plasma power supply;

[0006] Electrolyte is introduced into the chamber, and the ejector is controlled to ultrasonically vibrate to generate cavitation bubbles in the electrolyte to obtain a mixed fluid;

[0007] The voltage and duty cycle of the plasma power supply are adjusted so that the mixed fluid generates plasma through the jet outlet and generates a plasma oxidation layer on the surface of the workpiece.

[0008] The method for preparing coating by ultrasonic-assisted jet plasma according to the embodiment of the present application has at least the following beneficial effects:

[0009] In an embodiment of the present application, the ultrasonic cavitation effect and the micro-arc plasma oxidation method are combined, the electrolyte generates cavitation bubbles in the chamber to obtain a mixed fluid, and the mixed fluid generates plasma between the jet outlet and the workpiece surface, and then generates a plasma oxide layer on the workpiece surface. The plasma intensity is enhanced by ultrasonic cavitation, and the thickness of the oxide layer is increased.

[0010] In some embodiments of the present application, the voltage of the plasma power supply is 250V to 400V.

[0011] In some embodiments of the present application, the duty cycle of the plasma power supply is 30% to 60%.

[0012] By controlling the voltage and duty cycle of the plasma power supply, we can avoid the voltage or duty cycle being too low, resulting in poor plasma intensity, and the voltage or duty cycle being too high, resulting in plasma melting, which in turn reduces the thickness of the plasma oxide layer and affects the processing effect.

[0013] In some embodiments of the present application, the distance between the jet outlet and the surface of the workpiece is 0.1 mm to 10 mm.

[0014] In some embodiments of the present application, the amplitude of the ultrasonic vibration does not exceed 200 μm.

[0015] In some embodiments of the present application, the amplitude of the ultrasonic vibration does not exceed 25 μm.

[0016] In some embodiments of the present application, the shell is in the shape of a round rod.

[0017] In some embodiments of the present application, the length of the shell is 10 mm to 20 mm, and the diameter is 10 mm to 30 mm.

[0018] In some embodiments of the present application, a cross-sectional shape of the chamber along the axial direction of the shell includes any one of a rectangle, a diamond and a triangle, or a combination thereof.

[0019] In some embodiments of the present application, the cross-sectional area along the axial direction of the shell gradually increases from the jet outlet.

[0020] In some embodiments of the present application, the ejector is ultrasonically vibrated by an ultrasonic transducer.

[0021] In some embodiments of the present application, the workpiece is an anode and the ejector is a cathode.

[0022] In some embodiments of the present application, the electrolyte includes a salt solution, and the cations in the salt solution may be, for example, at least one cation of an element such as sodium, potassium, magnesium, calcium, aluminum, iron, cobalt, nickel, copper, zinc, etc., and the cations in the salt solution may be, for example, halogen ions (such as chloride ions, bromide ions), inorganic or organic acid radical ions (such as sulfate ions, nitrate ions, phosphate ions), etc. At least one of them. The concentration of the salt solution may be, for example, 0.5 mol / L or more, for example, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L. In some embodiments, the salt solution is a saturated salt solution. In some embodiments, the concentration of the salt solution is more than 50% of its saturated concentration, for example, 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 100% of the saturated concentration.

[0023] A second aspect of the present application provides a workpiece, which is processed by the aforementioned method for preparing a coating by ultrasonic-assisted jet plasma.

[0024] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the cross-sectional shape of the ejector along the axial direction of the shell in one embodiment of the present application.

[0026] Figure 2 It is a schematic diagram of the cross-sectional shape of the ejector along the axial direction of the shell in another embodiment of the present application.

[0027] Figure 3 This is a schematic diagram of the cross-sectional shape of the ejector along the axial direction of the shell in another embodiment of the present application.

[0028] Figure 4 The present invention is a flowchart of an ultrasonic-assisted fluid jet machining method according to an embodiment of the present application.

[0029] Figure 5 Schematic diagram of plasma region under different voltages in one embodiment of the present application, wherein (a) to (d) are the results when the voltage of the plasma power supply is 250V, 300V, 350V, and 400V, respectively.

[0030] Figure 6 Schematic diagram of the appearance of plasma oxide layer and micropores formed on the surface of a workpiece under different voltages in one embodiment of the present application, wherein (a) to (d) are the results of the plasma power supply voltage being 250V, 300V, 350V, and 400V, respectively.

[0031] Figure 7 Schematic diagram of the outline of the plasma oxide layer and micropores formed on the surface of a workpiece under different voltages in one embodiment of the present application.

[0032] Figure 8 This is a schematic diagram of the height and micropore depth of the plasma oxidation layer formed on the surface of a workpiece under different voltages in an embodiment of the present application.

[0033] Fig. 9 Schematic diagram of plasma region under different duty cycles in one embodiment of the present application, wherein (a) to (d) are the results when the duty cycles of the plasma power supply are 20%, 40%, 60%, and 80%, respectively.

[0034] Fig.10 Schematic diagram of the appearance of the plasma oxide layer and micropores formed on the surface of the workpiece under different duty cycles in one embodiment of the present application, wherein (a) to (d) are the results when the duty cycle of the plasma power source is 20%, 40%, 60%, and 80%, respectively.

[0035] Fig.11 Schematic diagram of the outline of the plasma oxide layer and micropores formed on the surface of a workpiece at different duty cycles in one embodiment of the present application.

[0036] Fig.12 This is a schematic diagram of the height and micropore depth of the plasma oxidation layer formed on the surface of a workpiece at different duty cycles in an embodiment of the present application.

[0037] Fig.13 Schematic diagram of plasma region under different ultrasonic amplitudes in one embodiment of the present application, wherein (a) to (f) are the results of ultrasonic amplitudes of the ultrasonic transducer being 0 μm, 16.6 μm, 18.8 μm, 21.5 μm, 23.6 μm, and 25.4 μm, respectively.

[0038] Fig.14 Schematic diagram of the appearance of the plasma oxide layer formed on the surface of the workpiece under different ultrasonic amplitudes in one embodiment of the present application. (a) to (f) are the results of the ultrasonic amplitude of the ultrasonic transducer being 0 μm, 16.6 μm, 18.8 μm, 21.5 μm, 23.6 μm, and 25.4 μm, respectively.

[0039] Fig.15 Schematic diagram of the outline of the plasma oxidation layer formed on the surface of a workpiece under different ultrasonic amplitudes in one embodiment of the present application.

[0040] Fig.16It is a highly schematic diagram of the plasma oxide layer formed by processing the surface of a workpiece under different ultrasonic amplitudes in one embodiment of the present application.

[0041] Reference numerals: housing 100 , chamber 110 , jet outlet 111 , jet inlet 112 , transducer 120 , workpiece 200 . DETAILED DESCRIPTION

[0042] The following will clearly and completely describe the concept of the present application and the technical effects produced in combination with the embodiments, so as to fully understand the purpose, features and effects of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of them. Based on the embodiments of the present application, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present application.

[0043] The embodiments of the present application are described in detail below. The described embodiments are exemplary and are only used to explain the present application, and should not be understood as limiting the present application.

[0044] In the description of this application, "several" means more than one, "more" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0045] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein are only for the purpose of describing the embodiments of this application and are not intended to limit this application.

[0046] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0047] refer to Figure 1, shows a schematic diagram of the structure of an ejector according to an embodiment of the present application. The ejector includes a housing 100, a chamber 110 is formed in the housing 100, the chamber 110 is used to contain electrolyte, and an ejection outlet 111 is provided at one end of the chamber 110. When working, the ejector is arranged opposite to the workpiece 220, and the ejection outlet 111 faces the position of the surface of the workpiece 200 to be processed.

[0048] In some embodiments, the chamber 110 is further provided with a jet inlet 112 at one end relative to the jet outlet 111, and the electrolyte is introduced into the chamber 110 through the jet inlet 112, and the fluid in the chamber is discharged from the jet outlet 111. In some other embodiments, the jet inlet 112 can also be set on the side wall of the housing 100 or other feasible positions, as long as the electrolyte can be introduced into the chamber 110 from the jet inlet 112. In some embodiments, the chamber 110 is connected to the jet inlet 112 and the jet outlet 111 through a jet channel. In some embodiments, the jet inlet 112, the jet outlet 111, and the jet channel connecting the jet inlet 112 and the jet outlet 111 are coaxially arranged. In some embodiments, the jet inlet 112, the jet outlet 111, the jet channel and the chamber 110 are coaxially arranged. In some embodiments, a switch portion is provided on the jet inlet 112 to realize the opening and closing of the jet inlet 112. In some embodiments, the electrolyte or fluid in the chamber 110 is confined in the chamber 110 under pressure, and leaves the chamber 110 through the jet outlet 111 when the pressure changes.

[0049] In some embodiments, an ultrasonic transducer 120 is also provided on the ejector, and the ultrasonic transducer 120 is used to provide the ejector with corresponding ultrasonic vibration conditions so that the electrolyte in the chamber 110 generates cavitation bubbles through ultrasonic vibration to form a gas-liquid mixed fluid. In some embodiments, the ultrasonic transducer 120 is arranged inside the shell 100 of the ejector; and in other embodiments, the ultrasonic transducer 120 is arranged outside the shell 100 of the ejector. In some embodiments, the ultrasonic transducer 120 is fixedly connected or detachably connected to the shell 100. In some embodiments, the ultrasonic transducer 120 is supported on the shell 100. In the above manner, the jet is turned on first, and then the ultrasonic vibration is turned on, the fluid will generate cavitation in the cavity, so that the jet becomes a gas-liquid mixed fluid; or the ultrasonic vibration is turned on first and then the jet is turned on, the above effect can also be achieved.

[0050] In some embodiments, the shell is in the shape of a round rod. It is understood that the round rod shape means that it is in the shape of a long strip or other shapes similar to a long strip in the axial direction, and in the shape of a circle or other shapes similar to a circle in the cross-sectional direction perpendicular to the axial direction. In some embodiments, the length of the shell (i.e., the length along the axial direction) is 10 mm to 20 mm, and the diameter (i.e., the diameter of the circle in the cross-sectional direction perpendicular to the axial direction) is 10 mm to 30 mm. In some embodiments, the cross-sectional shape of the chamber 110 along the axial direction of the shell 100 includes any one of a rectangle, a rhombus, and a triangle, or a combination thereof. For example, refer to Figure 1 to Figure 3 , Figure 1 The cross-sectional shape of the middle chamber 110 along the axial direction of the housing 100 is rectangular. Figure 2 The cross-sectional shape of the middle chamber 110 along the axial direction of the housing 100 is a rhombus, that is, the upper and lower parts of the cross-sectional shape are symmetrically arranged conical structures. Figure 3 The cross-sectional shape of the middle chamber 110 along the axial direction of the housing 100 is a combination of a rectangle and a triangle. In some embodiments, the cross-sectional area from the jet outlet 111 along the axial direction of the housing 100 (i.e., in the opposite direction of the flow of the electrolyte) gradually increases, that is, the area of ​​the triangular cross-section of the lower conical structure perpendicular to the ejector housing gradually decreases along the flow direction of the electrolyte, which can improve the cavitation effect of the electrolyte in the chamber and further improve the working efficiency of the processing method. In some embodiments, the size and shape of the chamber can be adjusted according to the size of the housing.

[0051] refer to Figure 4 , shows an ultrasonic-assisted jet machining method of an embodiment of the present application, the ultrasonic-assisted jet machining method involves the above-mentioned ejector, and the ultrasonic-assisted jet machining method includes the following steps S100 to S300.

[0052] Step S100: The ejector is arranged opposite to the workpiece to be processed, with the jet outlet facing the surface of the workpiece, and the workpiece and the ejector are connected to a plasma power supply respectively.

[0053] In some embodiments, the workpiece to be processed is the anode and the ejector is the cathode, and in this way, anodization is performed to achieve processing of the workpiece surface. In some embodiments, the transducer is connected to an ultrasonic power supply to drive the transducer to generate ultrasound. The surface of the ejector and the workpiece to be processed are respectively connected to a plasma power supply, that is, the workpiece to be processed is used as the anode and the surface of the ejector is used as the cathode, so that the workpiece surface is processed.

[0054] In some embodiments, the distance between the jet outlet and the surface of the workpiece is 0.1 mm to 10 mm, for example, 0.1 mm, 0.2 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.8 mm, 1 mm, 2 mm, 4 mm, 5 mm, 6 mm, 8 mm, 10 mm. If the distance between the jet outlet and the surface of the workpiece is too small or too large, the processing quality of the workpiece surface will be affected and the processing efficiency will be affected.

[0055] Step S200: Introduce electrolyte into the chamber, and control the ejector to vibrate ultrasonically, so that the electrolyte generates cavitation bubbles to obtain a mixed fluid. When the ejector is controlled to vibrate ultrasonically and a certain ultrasonic amplitude is applied, the electrolyte in the chamber will generate a pressure difference under the high-frequency ultrasonic vibration, and then bubbles will be stimulated, and the bubbles will break to form a local vacuum, that is, cavitation bubbles are generated to achieve the cavitation effect.

[0056] In some embodiments, the electrolyte is introduced into the chamber by a peristaltic pump, and the flow rate and rate of the electrolyte introduction can be controlled according to actual needs to ensure that plasma can be generated.

[0057] In some embodiments, the ultrasonic vibration generated by the ejector is controlled to be a longitudinal vibration (i.e., along the axial direction of the ejector), so that the electrolyte can reliably generate cavitation bubbles in the chamber and reduce the impact on the installation and positioning of the ejector. It is understandable that the ejector can also use other vibration forms known in the art to cause the electrolyte to generate cavitation bubbles in the chamber for subsequent steps, which is not limited here.

[0058] Step S300: Adjust the voltage and duty cycle of the plasma power supply so that the mixed fluid generates plasma through the jet outlet and generates a plasma oxide layer on the surface of the workpiece. Specifically, adjust the voltage and duty cycle of the plasma power supply for generating plasma so that the shell of the ejector is conductive, control the mixed fluid in the chamber of the ejector to pass through the jet outlet, and the mixed fluid generates plasma between the jet outlet and the surface of the workpiece, and generates a plasma oxide layer on the surface of the workpiece to meet the needs of specific processing.

[0059] By combining the ultrasonic cavitation effect with the micro-arc plasma oxidation method, the electrolyte generates cavitation bubbles in the chamber to obtain a mixed fluid, and the mixed fluid generates plasma between the jet outlet and the workpiece surface, thereby generating a plasma oxide layer on the workpiece surface. The plasma intensity is enhanced by ultrasonic cavitation, and the thickness of the oxide layer is increased. Plasma oxidation can generate a dense and uniform ceramic film layer on the metal surface. Its wear resistance and corrosion resistance are also significantly better than anodizing or hard anodizing films, which can significantly improve the service life of the workpiece.

[0060] Among them, the voltage of the plasma power supply for generating plasma is 250V to 400V, for example, it can be 250V, 300V, 350V, 400V. When the duty cycle of the plasma power supply is constant, the greater the voltage of the plasma power supply, the larger the diameter of the area where the plasma is generated, and the greater the intensity of the plasma. The duty cycle of the plasma power supply for generating plasma is 30% to 60%, for example, it can be 30%, 35%, 40%, 45%, 50%, 55%, 60%. When the voltage of the plasma power supply is constant, the greater the duty cycle, the longer the power supply voltage acts, the more helpful it is to improve the intensity of the plasma, and the greater the intensity of the plasma generated. In some embodiments, the duty cycle of the plasma power supply is 40-60%, 45-55%, and a plasma oxide layer can be generated on the surface of the workpiece, and the phenomenon of melting and removal of the workpiece material will not occur.

[0061] In some embodiments, the amplitude of the ultrasonic vibration of the ejector is less than 200 μm. When the voltage and duty cycle of the plasma power supply are constant, the larger the ultrasonic amplitude of the ejector, the stronger the plasma generated. In some embodiments, the amplitude of the ultrasonic vibration of the ejector is 0 to 200 μm, for example, it can be 0, 1 μm, 2 μm, 3 μm, 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm. Since the size of the ultrasonic amplitude directly determines the number of cavitation bubbles, only when the ultrasonic amplitude is within a suitable range can a suitable number of bubbles be excited, thereby enhancing the plasma and generating a plasma oxide layer.

[0062] In some embodiments, the length of the ejector is 10 mm to 20 mm, and the diameter is 10 mm to 30 mm. The ultrasonic amplitude of the ejector is 0 to 25 μm to stimulate a suitable number of cavitation bubbles, thereby enhancing the strength of the plasma.

[0063] It can be understood that the above-mentioned sequence of S100 to S300 is only the sequence in one embodiment of the present application. When the working conditions are met, the sequence of S100 to S300 can be reasonably adjusted without limitation. For example, S100 and S200 can be performed simultaneously, or the sequence can be reversed to perform S200 first and then S100. The voltage adjustment and duty cycle in S300 can also be pre-set when the plasma power supply is connected in S100.

[0064] In some embodiments, a mobile platform is provided to connect to the ejector, and the mobile platform can drive the ejector to translate according to a set trajectory to complete different processing requirements for different surfaces on the workpiece.

[0065] A second aspect of the present application provides a workpiece, which is machined using the aforementioned ultrasonic-assisted jet machining method.

[0066] In some embodiments, the workpiece includes a metal layer. In some embodiments, the metal element of the metal layer includes at least one of magnesium, aluminum, titanium, etc. In some embodiments, the metal layer includes a single substance, an alloy or a mixture of the metal element.

[0067] The present application is described below in conjunction with specific embodiments.

[0068] Example 1: Effect of plasma power supply on plasma oxide layer

[0069] This embodiment provides an ultrasonic assisted fluid jet processing method, and the fluid jet used is referenced Figure 1 , including a shell, a chamber 110 is formed in the shell 100, an ultrasonic transducer 120 is arranged outside the chamber 110, the chamber 110 has a jet channel arranged along the axial direction, and a jet inlet 112 and a jet outlet 111 are formed on the shell on both sides of the jet channel. The ultrasonic transducer is connected to an ultrasonic power supply, and the shell of the ejector and the titanium alloy workpiece 200 arranged opposite to the jet outlet 111 with a spacing of 10 mm are connected to a plasma power supply as a cathode and an anode respectively. A 2 mol / L NaSO4 solution is introduced into the chamber 110 from the jet inlet 112 as an electrolyte. The amplitude of the ultrasonic transducer is controlled to be 0 μm, and the duty cycle of the plasma power supply is controlled to be 50%, and the workpiece is processed under different voltage conditions of the plasma power supply.

[0070] During the processing, the size of the plasma generated by the jet outlet 111 is observed, and the results are as follows: Figure 5 As shown in the figure, when the duty cycle is 50%, as the voltage increases, the diameter of the plasma area gradually increases. When the voltage increases from 250V to 300V, then to 350V, and finally to 400V, the diameter of the plasma area increases from 0.52mm to 0.62mm, then to 0.72mm, and finally to 0.79mm. The results show that when the duty cycle is constant, the greater the voltage, the greater the intensity of the plasma.

[0071] The appearance of the plasma oxide layer formed on the workpiece surface was characterized by laser confocal microscopy. Figure 6 As shown, the plasma oxide layer was extracted using the laser confocal microscope's built-in software. The extraction results are shown in Figure 7The statistics of oxide layer height or hole depth are shown in Figure 8 As shown. It can be seen from the figure that when the duty cycle is 50%, when it does not exceed 350V, a plasma oxide layer higher than the original surface of the workpiece will grow after processing, and as the voltage increases, the protruding height of the plasma oxide layer relative to the original surface increases. At 350V, the height of the plasma oxide layer reaches 106.2μm. When the voltage is increased to 400V, a micropore with a depth of 132.7μm is generated on the surface of the workpiece, indicating that material removal has occurred at this time. This is because under high voltage, the high-energy plasma generated melts the workpiece material, and the molten material is immediately washed away by the jet. Therefore, the voltage needs to be controlled within the effective voltage range that does not produce material melting and removal. Therefore, the duty cycle is 50%, and the plasma power supply voltage is 250V to 400V, preferably 350V, then a plasma oxide layer can be generated on the surface of the workpiece, and the phenomenon of workpiece material melting and removal will not occur.

[0072] Example 2: Effects of different duty cycles on plasma oxide layer

[0073] Referring to the ultrasonic-assisted jet machining method of Example 1, the voltage of the plasma power supply is kept constant at 350V, and the workpiece is machined by adjusting different duty cycles of the plasma power supply.

[0074] During the processing, the size of the plasma generated by the jet outlet 111 is observed, and the results are as follows: Fig. 9 As shown. As the duty cycle increases, the diameter of the plasma region also shows a gradual increase trend. When the duty cycle increases from 20% to 40%, then to 60%, and finally to 80%, the diameter of the plasma region increases from 0.60mm to 0.68mm, then to 0.97mm, and finally to 1.14mm. That is, when the power supply voltage is constant, the larger the duty cycle and the longer the voltage action time, the more helpful it is to improve the intensity of the plasma.

[0075] The appearance of the plasma oxide layer formed on the workpiece surface was characterized by laser confocal microscopy. Fig.10 As shown, the plasma oxide layer was extracted using the laser confocal microscope's built-in software. The extraction results are shown in Fig.11 The statistics of oxide layer height or hole depth are shown in Fig.12As shown. It can be seen from the figure that when the power supply voltage is 350V, when the duty cycle increases from 20% to 40%, the height of the plasma oxide layer increases from 22.5μm to 46.5μm. When the duty cycle is further increased to 60%, it can be seen that the plasma oxide layer presents a shape with a convex edge of the middle depression. The height of the plasma oxide layer is 88.6μm, and the depth of the depression from the highest point is 72.0μm, indicating that at a duty cycle of 60%, plasma oxidation and plasma melting occur simultaneously, and plasma oxidation dominates, so the overall growth oxide layer. When the duty cycle rises to 80%, the morphology of the plasma oxide layer is similar to that of the duty cycle of 60%. The difference is that the height of the convexity of the plasma oxide layer is reduced to 63.4μm, and the depth of the depression from the highest point of the plasma oxide layer increases to 75.5μm, indicating that plasma melting under a duty cycle of 80% plays a dominant role, and ultimately manifests as the removal of workpiece material. Therefore, the duty cycle is set between 30% and 60%, preferably 50%, so that a plasma oxidation layer can be generated on the surface of the workpiece, and the workpiece material will not be melted and removed.

[0076] Example 3: Effects of different amplitudes on plasma oxidation layer

[0077] Referring to the ultrasonic-assisted jet machining method of Example 1, the voltage of the plasma power supply is kept constant at 350V, the duty cycle is kept constant at 50%, and the ultrasonic transducer is adjusted to different ultrasonic amplitudes to machine the workpiece.

[0078] During the processing, the size of the plasma generated by the jet outlet 111 is observed, and the results are as follows: Fig.13 As shown in the figure, with the increase of ultrasonic amplitude, the diameter of the plasma region shows a trend of increasing first and then decreasing. When no ultrasonic amplitude is applied, the diameter of the plasma region is 0.72mm, and when the ultrasonic amplitude is 18.8μm, the diameter of the plasma region increases to a maximum value of 1.09mm; then, when the ultrasonic amplitude continues to increase to 21.5μm, the diameter of the plasma region will shrink to 0.73mm, and when the ultrasonic amplitude increases to 25.4μm, the diameter of the plasma region will shrink to 0.56mm.

[0079] The appearance of the plasma oxide layer formed on the workpiece surface was characterized by laser confocal microscopy. Fig.14 As shown, the plasma oxide layer was extracted using the laser confocal microscope's built-in software. The extraction results are shown in Fig.15 The statistics of oxide layer height or hole depth are shown in Fig.16As shown in the figure, under the condition of power supply voltage of 350V and duty cycle of 50%, when the ultrasonic amplitude gradually increases from 0μm to 18.8μm, the height of the plasma oxide layer gradually increases from 106.2μm to 152.7μm; and when the ultrasonic amplitude continues to increase from 18.8μm to 25.4μm, the height of the oxide layer also gradually decreases from 152.7μm to 109.7μm. Since the size of the ultrasonic amplitude directly determines the number of cavitation bubbles, the ultrasonic amplitude can only excite a suitable number of bubbles within a suitable range, thereby enhancing the plasma and generating a plasma oxide layer.

[0080] Therefore, the ultrasonic amplitude of the transducer is 0 to 200 μm, that is, the ultrasonic amplitude is greater than 0 μm. When the power supply voltage and duty cycle for generating plasma are constant, the larger the ultrasonic amplitude is, the stronger the generated plasma is.

[0081] In this embodiment, when the length of the ejector is 10 mm to 20 mm and the diameter is 10 to 30 mm, the ultrasonic amplitude of the ejector rod 10 is 0 to 25 μm to stimulate a suitable number of cavitation bubbles, thereby enhancing the intensity of the plasma.

[0082] The present application is described in detail above in conjunction with the embodiments, but the present application is not limited to the above embodiments, and various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present application. In addition, the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

Claims

1. Ultrasonic assisted jet plasma coating preparation method, characterized in that: The following steps are involved: The ejector is arranged opposite to the workpiece to be processed, the ejector having a shell, a chamber for containing electrolyte formed in the shell, a jet outlet is arranged at one end of the chamber, the jet outlet is directed toward the surface of the workpiece, and the workpiece and the ejector are respectively connected to a plasma power supply; Introducing electrolyte into the chamber, and controlling the ejector to ultrasonically vibrate, so that cavitation bubbles are generated in the electrolyte to obtain a mixed fluid; The voltage and duty cycle of the plasma power supply are adjusted so that the mixed fluid generates plasma through the jet outlet and generates a plasma oxidation layer on the surface of the workpiece.

2. The method for preparing coating by ultrasonic-assisted jet plasma according to claim 1, characterized in that: The voltage of the plasma power supply is 250V to 400V, and / or the duty cycle of the plasma power supply is 30% to 60%.

3. The method for preparing coating by ultrasonic-assisted jet plasma according to claim 1, characterized in that: The distance between the jet outlet and the surface of the workpiece is 0.1 mm to 10 mm.

4. The method for preparing coating by ultrasonic-assisted jet plasma according to claim 1, characterized in that: The amplitude of the ultrasonic vibration is 0 to 200 μm.

5. The method for preparing coating by ultrasonic-assisted jet plasma according to claim 4, characterized in that: The amplitude of the ultrasonic vibration does not exceed 25 μm.

6. The method for preparing coating by ultrasonic-assisted jet plasma according to claim 1, characterized in that: The shell is in the shape of a round rod, and the length of the shell is 10 mm to 20 mm, and the diameter of the shell is 10 mm to 30 mm.

7. The method for preparing coating by ultrasonic-assisted jet plasma according to claim 1, characterized in that: The ejector is caused to generate ultrasonic vibration by an ultrasonic transducer.

8. The method for preparing coating by ultrasonic-assisted jet plasma according to claim 1, characterized in that: The workpiece is an anode and the ejector is a cathode.

9. The method for preparing coating by ultrasonic-assisted jet plasma according to claim 1, characterized in that: The electrolyte includes a salt solution.

10. A workpiece, characterized in that The coating is prepared by the method for preparing the coating by ultrasonic-assisted jet plasma as described in any one of claims 1 to 9.

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