A current-carrying friction processing method for preparing a gradient nanocrystalline structure layer on a metal coating surface

Abstract

The application discloses a current-carrying friction processing method for preparing a gradient nanocrystalline structure layer on a metal coating surface, relates to the technical field of metal coating processing, and comprises the following steps: preparing a metal coating on the surface of a base body, polishing the metal coating with sandpaper, and cleaning the surface; connecting the metal coating to direct current, and performing current-carrying friction treatment on the whole region to be processed; different current voltages and grinding processes are adopted for different metal coating materials; the synergistic effect of an electric system and a friction system is utilized to make the crystal grains of the metal coating generate high-density dislocations, stacking faults, atomic rearrangement, intergranular thermal effects and the like at a microscale, so that the coarse crystal grains are converted into fine crystal grains, and the metal coating surface obtains a gradient nanocrystalline; and the application can realize the preparation of a large-area, high-forming-rate and structure-clear gradient nanocrystalline structure layer. The application solves the problems of complex process, low forming rate and structure ambiguity in the traditional preparation of a gradient nanocrystalline structure layer.

Description

Technical Field

[0001] This invention relates to the field of metal coating processing technology, and in particular to a current-carrying triboprocessing method for preparing a gradient nanocrystalline structure layer on the surface of a metal coating. Background Technology

[0002] Gradient nanocrystalline structures refer to materials where grain size gradually changes from one region to another, forming a gradient. Forming gradient nanocrystalline structures within or on the surface of a material can effectively achieve the following superior properties: mechanical properties: providing high strength and hardness (nanocrystalline regions), while offering better ductility and toughness in another region (larger grain regions); wear resistance: providing high surface hardness, thus enhancing wear resistance; reduced crack propagation rate: crack propagation is hindered in regions with different grain sizes, thereby reducing its propagation rate; composite functionality: gradient nanocrystalline structures can integrate multiple properties in a single material according to different application requirements, such as bonding strength, electrical conductivity, and thermal conductivity. In summary, introducing gradient nanocrystalline structures into the coating surface can effectively improve the coating's hardness, ductility, wear resistance, and corrosion resistance, thereby significantly extending the material's service life.

[0003] Common methods for preparing surface nanocrystals include high-energy shot peening (HESP), surface mechanical polishing (SMAT), and surface mechanical rolling. These methods involve repeated plastic deformation of the metal surface to achieve grain refinement. However, traditional methods for preparing gradient nanocrystal structures often suffer from problems such as unclear structures, low yield, and shallow forming regions, resulting in suboptimal gradient nanocrystal structures. Summary of the Invention

[0004] In view of the shortcomings of the above-mentioned technologies, the present invention aims to provide a current-carrying triboprocessing method for preparing gradient nanocrystalline structure layers on the surface of metal coatings, thereby solving the problems of structural ambiguity and shallow forming area in the preparation of gradient nanocrystalline structure layers on metal coatings.

[0005] To address the aforementioned technical shortcomings, the present invention is implemented through the following technical solution:

[0006] A current-carrying triboprocessing method for preparing a gradient nanocrystalline structure layer on a metal coating surface includes the following steps:

[0007] Step S1: Prepare a metal coating on the substrate surface, sand the metal coating, and clean the surface.

[0008] Step S2: Connect the metal coating to DC power and perform current-carrying friction treatment on the entire area to be processed;

[0009] Step S3: For different metal coating materials, different currents, voltages, and grinding processes are used to obtain a gradient nanocrystalline structure layer with a large area, high formability, and clear structure.

[0010] Further, the coating preparation in step S1 includes:

[0011] Step S11, Solution preparation: Silver nitrate concentration is 16-48 g / L, glyoxal is 25-50 ml / L, triethanolamine is 5-10 ml / L, and 2% ammonia is added; the silver nitrate solution is mixed with 2% ammonia to obtain a silver ammonia solution; glyoxal and triethanolamine are mixed to obtain a reducing agent;

[0012] Step S12, Rotary spray deposition of silver coating: spray flow rate is 5-16 ml / min, spray distance is 3-7 cm, spray time is 5-30 min, spray air pressure is 0.2-1 MPa, and rotation speed is 60-150 r / min;

[0013] Step S13: Polish the silver coating with SiC sandpaper. Use SiC sandpaper with grits of 1000#, 1500#, 2000# and 3000# in sequence to polish the coating surface. Place it in a container of anhydrous ethanol for ultrasonic cleaning for 15 minutes.

[0014] Furthermore, the metal coating material includes any one or a combination of iron, nickel, gold, silver, copper, aluminum, and magnesium, and the coating thickness is greater than 5 μm.

[0015] Furthermore, the metal coating preparation method includes any one of electroplating, electroless plating, magnetron sputtering, spray deposition, thermal spraying, and cold spraying.

[0016] Furthermore, the mechanical grinding method includes any one of cylindrical grinding, ball-disc reciprocating friction, and pin-disc friction.

[0017] Furthermore, the DC current has a current of 1–20A and a voltage of 5–50V.

[0018] Furthermore, in the aforementioned grinding process, the load is 1–50 N, the friction time is 10–180 minutes, and the friction frequency is 1–10 Hz.

[0019] Furthermore, in step S3, the silver coating surface is subjected to current-carrying friction processing using a pin-disc friction method; the silver coating is connected to a DC current of 2A, the load is 3N, the friction time is 30 minutes, and the friction frequency is 1Hz.

[0020] Furthermore, in step S3, the silver coating surface is subjected to current-carrying friction processing using a pin-disc friction method; the silver coating is connected to a DC current of 2A, the load is 0.5N, the friction time is 20 minutes, and the friction frequency is 1Hz.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] This invention provides a current-carrying triboprocessing method for preparing gradient nanocrystalline structure layers on metal coating surfaces. This method achieves gradient nanocrystalline structure layers on metal coatings through current-carrying triboprocessing. Microscopically, shear stress within the grains leads to the generation of numerous dislocations, stacking faults, atomic rearrangements, and large-angle grain boundaries. Simultaneously, current flow is obstructed under these conditions, generating a "thermal effect," further promoting dislocations and accelerating the transformation of grains from coarse to fine grains, thus achieving grain refinement. As the coating depth increases, the shear stress and normal pressure are gradually weakened, and the number of coarse grains being cut into fine grains begins to decrease, thereby gradually forming a gradient nanocrystalline structure layer. Through the synergistic effect of the triboprocessing system and the electrical system, a gradient nanocrystalline structure layer with a large area, clear structure, and high formability is effectively prepared. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a TEM image of the cross-section of the silver coating of Embodiment 1 of the present invention after undergoing current-carrying friction processing.

[0025] Figure 2 This is a statistical diagram of the grain size of the silver coating gradient nanocrystalline structure layer in Example 1 of the present invention.

[0026] Figure 3 This is a load-displacement curve of the silver coating surface of Example 1 of the present invention, characterized by nanoindentation.

[0027] Figure 4 This is a load-displacement curve of the silver coating surface of Embodiment 2 of the present invention, characterized by nanoindentation. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] The following is in conjunction with the appendix Figure 1-4 The present invention will be described in further detail below.

[0030] A current-carrying triboprocessing method for preparing a gradient nanocrystalline structure layer on a metal coating surface includes the following steps:

[0031] Step S1: Prepare a metal coating on the substrate surface, sand the metal coating, and clean the surface.

[0032] Step S2: Connect the metal coating to DC power and perform current-carrying friction treatment on the entire area to be processed;

[0033] Step S3: For different metal coating materials, different currents, voltages, and grinding processes are used to obtain a gradient nanocrystalline structure layer with a large area, high formability, and clear structure.

[0034] Specifically, in this embodiment, the coating preparation in step S1 includes:

[0035] Step S11, Solution preparation: Silver nitrate concentration is 16-48 g / L, glyoxal is 25-50 ml / L, triethanolamine is 5-10 ml / L, and 2% ammonia is added; the silver nitrate solution is mixed with 2% ammonia to obtain a silver ammonia solution; glyoxal and triethanolamine are mixed to obtain a reducing agent;

[0036] Step S12, Rotary spray deposition of silver coating: spray flow rate is 5-16 ml / min, spray distance is 3-7 cm, spray time is 5-30 min, spray air pressure is 0.2-1 MPa, and rotation speed is 60-150 r / min;

[0037] Step S13: Polish the silver coating with SiC sandpaper. Use SiC sandpaper with grits of 1000#, 1500#, 2000# and 3000# in sequence to polish the coating surface. Place it in a container of anhydrous ethanol for ultrasonic cleaning for 15 minutes.

[0038] Specifically, in this embodiment, the metal coating material includes any one or a combination of iron, nickel, gold, silver, copper, aluminum, and magnesium, and the coating thickness is greater than 5 μm.

[0039] Specifically, in this embodiment, the method for preparing the metal coating includes any one of electroplating, chemical plating, magnetron sputtering, spray deposition, thermal spraying, and cold spraying.

[0040] Specifically, in this embodiment, the mechanical grinding method includes any one of cylindrical grinding, ball-disc reciprocating friction, and pin-disc friction.

[0041] Specifically, in this embodiment, the DC current is 1-20A and the voltage is 5-50V.

[0042] Specifically, in this embodiment, the grinding process has a load of 1-50N, a friction time of 10-180 minutes, and a friction frequency of 1-10Hz.

[0043] Example 1

[0044] A current-carrying triboprocessing method for preparing a gradient nanocrystalline structure layer on a metal coating surface, the specific operation steps of which are as follows:

[0045] Step 1: Coating preparation.

[0046] Solution preparation: Silver nitrate concentration 16–48 g / L, glyoxal 25–50 ml / L, triethanolamine 5–10 ml / L, 2% ammonia. Mix the silver nitrate solution with 2% ammonia to obtain a silver ammonia solution. Mix glyoxal and triethanolamine to obtain a reducing agent.

[0047] Rotary spray deposition of silver coating: spray flow rate of 5-16 ml / min, spray distance of 3-7 cm, spray time of 5-30 min, spray air pressure of 0.2-1 MPa, and rotation speed of 60-150 r / min.

[0048] Step 2: Polish the silver coating with SiC sandpaper. Use SiC sandpaper with grits of 1000#, 1500#, 2000#, and 3000# in sequence to polish the coating surface. Place the coating in a container of anhydrous ethanol and perform ultrasonic cleaning for 15 minutes.

[0049] Step 3: Perform current-carrying friction processing on the silver coating surface using a pin-disc friction method. Connect the silver coating to a DC current of 2A, with a load of 3N, a friction time of 30 minutes, and a friction frequency of 1Hz.

[0050] Step 4: Clean the surface of the processed silver coating by ultrasonic cleaning in a container of anhydrous ethanol for 15 minutes.

[0051] The prepared silver coating and the processed silver coating were characterized by the following tests:

[0052] 1) The average thickness of the silver coating is 48 μm.

[0053] 2) The silver coating was characterized by X-ray diffraction. The average size of the silver grains in the silver coating before processing was 130 nm.

[0054] 3) TEM characterization of the cross-section of the silver coating after surface processing confirmed that the coating formed a gradient nanocrystalline structure layer, and the grain size was statistically analyzed, with an average grain size of 42 nm.

[0055] 4) The resistivity of the silver coating before and after processing was tested. The resistivity before processing was 1.72 × 10⁻⁶. -8 Ω·m, the resistivity after processing is 1.81×10⁻⁶. -8 The resistivity increases slightly by Ω·m.

[0056] 5) Nano-indentation characterization was performed on the silver coating before and after processing. The hardness before processing was 1.78 GPa and the hardness after processing was 2.81 GPa, indicating that the hardness of the silver coating was improved after processing.

[0057] Example 2

[0058] A current-carrying triboprocessing method for preparing a gradient nanocrystalline structure layer on a metal coating surface, the specific operation steps of which are as follows:

[0059] Step 1: Deposit a pure silver coating on a stainless steel substrate using magnetron sputtering for 5 hours.

[0060] Step 2: Due to the low surface roughness of the silver coating prepared by magnetron sputtering, surface polishing is unnecessary. The silver coating surface is then subjected to current-carrying triboelectric processing using a pin-disc friction method. A direct current of 2A is applied to the silver coating, the load is 0.5N, the friction time is 20 minutes, and the friction frequency is 1Hz.

[0061] Step 4: Clean the surface of the processed silver coating by ultrasonic cleaning in a container of anhydrous ethanol for 15 minutes.

[0062] The prepared silver coating and the processed silver coating were characterized by the following tests:

[0063] 1) The average thickness of the silver coating is 6 μm.

[0064] 2) The silver coating was characterized by X-ray diffraction. The average size of the silver grains in the silver coating before processing was 250 nm.

[0065] 3) TEM characterization of the cross-section of the silver coating after surface processing confirmed that the coating formed a gradient nanocrystalline structure layer, and the grain size was statistically analyzed, with an average grain size of 110 nm.

[0066] 4) The resistivity of the silver coating before and after processing was tested. The resistivity before processing was 1.69 × 10⁻⁶. -8 Ω·m, the resistivity after processing is 1.71×10⁻⁶. -8 The resistivity increases slightly by Ω·m.

[0067] 5) Nano-indentation characterization was performed on the silver coating before and after processing. The hardness before processing was 1.2 GPa, and the hardness after processing was 1.98 GPa, indicating that the hardness of the silver coating was improved after processing.

[0068] Comparative Example 1

[0069] A current-carrying triboprocessing method for preparing a gradient nanocrystalline structure layer on a metal coating surface, the specific operation steps of which are as follows:

[0070] Step 1: Coating Preparation

[0071] Solution preparation: Silver nitrate concentration 16–48 g / L, glyoxal 25–50 ml / L, triethanolamine 5–10 ml / L, 2% ammonia. Mix the silver nitrate solution with 2% ammonia to obtain a silver ammonia solution. Mix glyoxal and triethanolamine to obtain a reducing agent.

[0072] Rotary spray deposition of silver coating: spray flow rate of 5-16 ml / min, spray distance of 3-7 cm, spray time of 5-30 min, spray air pressure of 0.2-1 MPa, and rotation speed of 60-150 r / min.

[0073] Step 2: Polish the silver coating with SiC sandpaper. Use SiC sandpaper with grits of 1000#, 1500#, 2000#, and 3000# in sequence to polish the coating surface. Place the coating in a container of anhydrous ethanol and perform ultrasonic cleaning for 15 minutes.

[0074] Step 3: The silver coating surface is subjected to friction processing using a pin-disc friction method. The load is 3N, the friction time is 30 minutes, and the friction frequency is 1Hz.

[0075] Step 4: Clean the surface of the processed silver coating by ultrasonic cleaning in a container of anhydrous ethanol for 15 minutes.

[0076] The prepared silver coating and the processed silver coating were characterized by the following tests:

[0077] 1) The average thickness of the silver coating is 48 μm.

[0078] 2) The silver coating was characterized by X-ray diffraction. The average size of the silver grains in the silver coating before processing was 130 nm.

[0079] 3) TEM characterization of the cross-section of the silver coating after surface processing revealed only a grain refinement region with a depth of 500 nm and an average grain size of 105 nm. No large-area and clearly structured gradient nanocrystalline structure layer was observed.

[0080] 4) The resistivity of the silver coating before and after processing was tested. The resistivity before processing was 1.72 × 10⁻⁶. -8 Ω·m, the resistivity after processing is 2.11×10 -8 The resistivity increases slightly by Ω·m.

[0081] 5) Nano-indentation characterization of the silver coating before and after processing showed that the hardness before processing was 1.78 GPa and the hardness after processing was 1.91 GPa, indicating that the hardness of the silver coating increased very little after processing.

[0082] Compared with existing technologies, the beneficial effects of this invention are as follows:

[0083] This invention provides a current-carrying triboprocessing method for preparing gradient nanocrystalline structure layers on metal coating surfaces. This method achieves gradient nanocrystalline structure layers on metal coatings through current-carrying triboprocessing. Microscopically, shear stress within the grains leads to the generation of numerous dislocations, stacking faults, atomic rearrangements, and large-angle grain boundaries. Simultaneously, current flow is obstructed under these conditions, generating a "thermal effect," further promoting dislocations and accelerating the transformation of grains from coarse to fine grains, thus achieving grain refinement. As the coating depth increases, the shear stress and normal pressure are gradually weakened, and the number of coarse grains being cut into fine grains begins to decrease, thereby gradually forming a gradient nanocrystalline structure layer. Through the synergistic effect of the triboprocessing system and the electrical system, a gradient nanocrystalline structure layer with a large area, clear structure, and high formability is effectively prepared.

[0084] The technical solutions provided by the embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the embodiments of the present invention. The descriptions of the embodiments above are only intended to help understand the principles of the embodiments of the present invention. Furthermore, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the embodiments of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A current-carrying triboprocessing method for preparing a gradient nanocrystalline structure layer on a metal coating surface, characterized in that, Includes the following steps: Step S1: A silver coating is deposited by rotary spraying using silver ammonia solution and reducing agent, with a coating thickness greater than 5 μm; the metal coating is then sanded with sandpaper and ultrasonically cleaned in anhydrous ethanol for 15 minutes to achieve surface cleaning. Step S2: Connect the metal coating to a DC power source, wherein the current is 1~20A and the voltage is 5~50V. Use any one of the mechanical grinding methods, such as cylindrical grinding, ball-disc reciprocating friction, or pin-disc friction, to perform current-carrying friction on the entire area to be processed. Step S3: For different metal coating materials, different grinding processes are adopted. The grinding process has a load of 1~50N, a friction time of 10~180 minutes, and a friction frequency of 1~10Hz. Among them, for silver coating, when using the pin-disc friction method, the current is 2A, the load is 3N, the friction time is 30 minutes, and the friction frequency is 1Hz, or the load is 0.5N, the friction time is 20 minutes, and the friction frequency is 1Hz, thereby obtaining a gradient nanocrystalline structure layer.

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