A method of producing a metal carbide coating

Abstract

The application discloses a preparation method of a metal carbide coating, which comprises the following steps: mixing metal carbide particles and metal binders in proportion, loading the mixture into a metal thin-walled tube, and pressing the metal thin-walled tube into a coating sheet through a roller press; stacking a metal sheet on the coating sheet and stacking the two together on the surface of a metal base to form a cladding assembly; placing the cladding assembly on an operation platform, fixing a tungsten electrode to a moving platform, making the moving platform drive the tungsten electrode to move in X and Y axial directions above the cladding assembly, and connecting the tungsten electrode and the base to the positive and negative poles of a pulse power source respectively; after power-on, the coating sheet is melted on the surface of the base to form a coating, and argon is introduced to protect a discharge area. The method provided by the application is simple in equipment, strong in operability, wide in practicability, and capable of realizing the preparation of all conductive metal carbide coatings.

Description

Technical Field

[0001] This invention relates to the field of metal materials technology, and specifically to a method for preparing a metal carbide coating. Background Technology

[0002] Cladding refers to a process in which a selected coating material is placed on the surface of a substrate using different fillers. Through heat transfer, the coating material and the substrate surface melt simultaneously and solidify rapidly to form a surface coating with extremely low dilution that is metallurgically bonded to the substrate material. This process significantly improves the wear resistance, corrosion resistance, heat resistance, oxidation resistance, and electrical properties of the substrate material.

[0003] Carbide coatings are coatings prepared on the surface of a substrate, with tungsten carbide as their main component. Tungsten carbide is a very hard ceramic material with excellent properties such as high melting point, high hardness, high wear resistance, and high corrosion resistance. Applying tungsten carbide coatings to metal surfaces can improve the hardness, wear resistance, corrosion resistance, and high-temperature resistance of the metal surface, and it is widely used in tools, molds, aerospace, automotive, and machinery industries.

[0004] Currently, the common methods for preparing carbide coatings include electroplating, electroless plating, vapor deposition, hot-dip galvanizing, thermal spraying, and cladding. Hot cladding, as an efficient and commonly used coating preparation method, mainly includes plasma cladding and laser cladding. Both plasma cladding and laser cladding utilize wind power to transport coating powder to form coating material on the surface of the substrate. The cladding process needs to be carried out on a special machine tool, which has a high equipment cost. Moreover, due to the large difference in density between carbides and metal binders, the use of wind transport will cause the separation of light and heavy particles, resulting in poor uniformity of the coating structure. Summary of the Invention

[0005] To address the above problems, this invention provides a method for preparing a metal carbide coating.

[0006] The technical solution adopted in this invention is:

[0007] A method for preparing a metal carbide coating includes the following steps:

[0008] (1) Fabrication of a metal substrate;

[0009] (2) After mixing metal carbide particles with metal binder in a certain proportion, the mixture is loaded into a metal thin-walled tube and the metal thin-walled tube is pressed into a coating sheet by a roller press.

[0010] (3) A metal sheet is stacked on top of the coating sheet, and the two are stacked together on the surface of the metal substrate to form a cladding assembly;

[0011] (4) Place the cladding assembly on the operating platform, fix the tungsten electrode on the motion platform, and drive the tungsten electrode to move in the X and Y axes above the cladding assembly so that the tungsten electrode and the substrate are respectively connected to the positive and negative terminals of the pulse power supply.

[0012] (5) After power is applied, the gap between the tungsten electrode and the cladding component is broken down by high voltage, and the arc current is used to keep it continuously discharged. Finally, the instantaneous high temperature generated by the high current pulse of the pulse power supply melts the coating sheet on the substrate surface to form a coating. At the same time, argon gas is introduced to protect the discharge area.

[0013] A metal sheet is stacked on top of the coating sheet, and the metal sheet is used as a protective layer. This not only prevents the metal carbide from melting due to excessive local temperature during the cladding process, but also allows the heat to be transferred evenly to the coating sheet through the metal sheet, resulting in a more uniform coating structure.

[0014] Furthermore, the metal carbide particles are tungsten carbide or titanium carbide, with a particle size of 10 μm to 200 μm.

[0015] Furthermore, the metal binder is iron, nickel, or cobalt, with a particle size of 1 μm to 100 μm.

[0016] Furthermore, the metal sheet is made of the same material as the metal adhesive, with a thickness of 0.5mm to 2mm and a width of 2mm to 4mm. This avoids introducing impurities and ensures coating performance.

[0017] Furthermore, the mixing ratio of metal carbide particles to metal binder is 1:4 to 4:1 by mass.

[0018] Furthermore, the thin-walled metal tube is a stainless steel tube with a wall thickness of 0.05mm to 0.5mm and an outer diameter of 2mm to 3mm.

[0019] Furthermore, in step 2), the coating sheet has a thickness of 0.5 mm to 3 mm and a width of 2 mm to 4 mm.

[0020] Furthermore, the maintenance current of the pulse power supply is 4A to 20A, the peak current of the high-current pulse is 1000A to 5000A, the pulse width is 100μs to 100ms, and the duty cycle is 1:(1 to 10).

[0021] Furthermore, the motion speed of the motion platform is 0.1 mm / s to 10 mm / s.

[0022] Furthermore, the net distance between the tungsten electrode and the cladding assembly is 3-5 mm.

[0023] The beneficial effects of this invention are:

[0024] (1) The present invention uses a pre-coated sheet to prepare the coating, which is simple to operate, low in cost, and can obtain a uniform coating. At the same time, the metal sheet placed on the top of the coating sheet can be used as a protective layer to further improve the uniformity of the coating structure and improve the wear resistance and corrosion resistance of the coating.

[0025] (2) The present invention uses arc current for preheating and heat preservation, and uses pulsed high current for coating cladding, which can avoid the generation of cracks during the coating process and further improve the uniformity of the coating structure, and improve the wear resistance and corrosion resistance of the coating. Attached Figure Description

[0026] Figure 1 This is a schematic diagram illustrating the preparation principle of the present invention.

[0027] Figure 2 The image shows the microstructure of the tungsten carbide coating prepared in Example 1.

[0028] Figure 3 The image shows the microstructure of the tungsten carbide coating prepared in Comparative Example 1.

[0029] Figure 4 The image shows the microstructure of the tungsten carbide coating prepared in Comparative Example 2.

[0030] Figure 5 The image shows the microstructure of the titanium carbide coating prepared in Example 2. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and a preferred embodiment.

[0032] The devices used in the following embodiments and comparative examples are all prior art. For example, the motion platform is driven by three motors and can be raised and lowered along the X, Y, and Z axes. The motion platform is mounted above an operating platform via a bracket. The XY axis movement speed is 0.1 mm / s-10 mm / s. A tungsten electrode is fixed on the motion platform, and argon gas passes through the tungsten electrode with the nozzle facing the operating platform. The pulse power supply has high-voltage ignition, arc maintenance, and high-current pulse modules. The maintenance current is 4A-20A, the peak current of the high-current pulse is 1000A-5000A, the pulse width is 100μs-100ms, and the duty cycle is 1:1-1:10.

[0033] Example 1

[0034] Preparation of tungsten carbide coating

[0035] (1) Using 304 stainless steel as the base material, the dimensions are 100mm×50mm×5mm;

[0036] (2) Select a 304 stainless steel pipe with an inner diameter of 2 mm and a wall thickness of 0.05 mm as a container. Mix 20% cobalt and 80% tungsten carbide powder evenly and fill it into the container. Press it into a coating sheet with a thickness of 1 mm and a width of 3 mm. The average particle size of tungsten carbide powder is 100 μm and the particle size of cobalt powder is 10 μm.

[0037] (3) Place the substrate on the operating platform, place a coating sheet on the substrate, and place a cobalt sheet with a thickness of 1 mm and a width of 2 mm on the coating sheet;

[0038] (4) Connect the tungsten electrode and the substrate to the positive and negative terminals of the pulse power supply, respectively. The arc current is 10A, the peak current of the high-current pulse is 2000A, the pulse width is 50ms, the duty cycle is 1:10, the tungsten electrode movement speed is 1mm / s, and the argon flow rate is 10L / min. Perform coating cladding according to the above parameters to obtain a tungsten carbide coating.

[0039] The microstructure of the tungsten carbide coating obtained by scanning electron microscopy is shown below. Figure 2 ,from Figure 2 It can be seen that the coating and the substrate material exhibit metallurgical bonding, and the tungsten carbide is evenly distributed in the coating and basically maintains the integrity of the particles.

[0040] The average thickness of the tungsten carbide coating was 2 mm, the overall hardness was 3.5 times that of the substrate, and the hardness of the tungsten carbide hard particles was 2000 HV.

[0041] Comparative Example 1

[0042] Compared to Example 1, all other parameters remained unchanged, except that no metal sheet was placed on the coating sheet.

[0043] The results of scanning the metal coating using electron microscopy are shown in the figure. Figure 3 ,from Figure 3 It can be seen that the coating and the substrate material also exhibit metallurgical bonding, but the content of intact tungsten carbide particles in the coating is significantly reduced. This is because, under the high temperature of the electric arc, some of the tungsten carbide completely melts and reacts with cobalt to form a new compound.

[0044] Comparative Example 2

[0045] Compared to Example 1, all other parameters remain unchanged except that the arc current is not used.

[0046] The results of scanning the metal coating using electron microscopy are shown in the figure. Figure 4 ,from Figure 4 It can be seen that there are many cracks in the coating, and the proportion of cracks that penetrate the coating is very high. Friction and wear tests show that the coating is prone to peeling off due to the presence of cracks.

[0047] Example 2

[0048] Preparation of titanium carbide coating

[0049] (1) 45 steel is the base material, and the size is 100mm×50mm×10mm;

[0050] (2) Select a 304 stainless steel pipe with an inner diameter of 2.5 mm and a wall thickness of 0.1 mm as a container. Mix 30% nickel and 70% titanium carbide powder by mass evenly and fill it into the container. Press it into a coating sheet with a thickness of 1 mm and a width of 4 mm. The average particle size of titanium carbide powder is 75 μm and the particle size of nickel powder is 5 μm.

[0051] (3) Place the substrate on the operating platform, place the coating sheet on the substrate, and place a nickel sheet with a thickness of 1 mm and a width of 3 mm on the coating sheet;

[0052] (4) Connect the tungsten electrode and the substrate to the positive and negative terminals of the pulse power supply respectively. The arc current is 15A, the peak current of the large current pulse is 3000A, the pulse width is 100ms, the duty cycle is 1:10, the tungsten electrode movement speed is 1.5mm / s, and the argon flow rate is 15L / min. Perform coating cladding according to the above parameters to obtain a titanium carbide coating.

[0053] The microstructure of the titanium carbide coating obtained by scanning electron microscopy is shown below. Figure 5 ,from Figure 5 It can be seen that the coating and the substrate material exhibit a metallurgical bond, and the titanium carbide is evenly distributed in the coating while maintaining the integrity of the particles.

[0054] The average thickness of the titanium carbide coating was 2 mm, and its overall hardness was 4 times that of the substrate. The hardness of the titanium carbide hard particles was 2600 HV.

[0055] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also within the protection scope of the present invention.

Claims

1. A method for preparing a metal carbide coating, characterized in that, Includes the following steps: (1) Fabrication of a metal substrate; (2) After mixing metal carbide particles with metal binder in a certain proportion, the mixture is loaded into a metal thin-walled tube and pressed into a coating sheet by a roller press; (3) Metal sheets are stacked on top of the coating sheet and the two are stacked together on the surface of the metal substrate to form a cladding assembly; (4) Place the cladding assembly on the operating platform, fix the tungsten electrode on the motion platform, and the motion platform drives the tungsten electrode to move in the X and Y axes above the cladding assembly so that the tungsten electrode and the substrate are respectively connected to the positive and negative terminals of the pulse power supply; (5) After power is applied, the gap between the tungsten electrode and the cladding assembly is broken down by high voltage, and the maintenance current is used to keep it continuously discharging. Finally, the instantaneous high temperature generated by the high current pulse of the pulse power supply melts the coating sheet on the substrate surface to form a coating. At the same time, argon gas is introduced to protect the discharge area. The metal sheet is made of the same material as the metal adhesive, and its thickness is 0.5mm to 2mm; The thin-walled metal tube is a stainless steel tube with a wall thickness of 0.05mm to 0.5mm and an outer diameter of 2mm to 3mm.

2. The method for preparing the metal carbide coating according to claim 1, characterized in that: The metal carbide particles are tungsten carbide or titanium carbide, with a particle size of 10 μm to 200 μm.

3. The method for preparing the metal carbide coating according to claim 1, characterized in that: The metal binder is made of iron, nickel, or cobalt, with a particle size of 1 μm to 100 μm.

4. The method for preparing a metal carbide coating according to claim 1, characterized in that: The width of the metal sheet is 2mm to 4mm.

5. The method for preparing a metal carbide coating according to claim 1, characterized in that: The mixing ratio of metal carbide particles to metal binder is 1:4 to 4:1 by mass.

6. The method for preparing a metal carbide coating according to claim 1, characterized in that: In step 2), the coating sheet has a thickness of 0.5 mm to 3 mm and a width of 2 mm to 4 mm.

7. The method for preparing a metal carbide coating according to claim 1, characterized in that: The pulse power supply has an arc current of 4A to 20A, a peak current of 1000A to 5000A for the high current pulse, a pulse width of 100μs to 100ms, and a duty cycle of 1:(1 to 10).

8. The method for preparing a metal carbide coating according to claim 1, characterized in that: The motion platform has a motion speed of 0.1 mm / s to 10 mm / s.

9. The method for preparing a metal carbide coating according to claim 1, characterized in that: The net distance between the tungsten electrode and the cladding assembly is 3-5 mm.

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