A friction-reducing coating for cutting tools and its preparation method

Abstract

This invention discloses a friction-reducing coating for cutting tools and its preparation method, belonging to the technical field of metal cutting tools. The friction-reducing coating for cutting tools includes a hard coating layer and a soft coating layer arranged from the inside out. The hard coating layer comprises multiple hard coating textures spaced apart on the surface of the cutting tool, with the length direction of the hard coating textures perpendicular to the chip friction direction. A soft coating layer fills the spaces between adjacent hard coating textures. The hard coating textures consist of a hard coating matrix and a dispersed reinforcing phase therein, while the soft coating layer consists of a lubricating material. The outermost soft coating material effectively reduces friction during the cutting process, thereby reducing frictional heat generation and inhibiting the formation of built-up edge. Below the soft coating layer, the soft coating material and the hard coating texture materials are spaced apart on the same plane. During friction, the hard coating textures mainly bear the contact pressure and improve the wear resistance of the cutting tool, while the soft coating layer is squeezed to the friction interface under the contact pressure to continue the lubrication effect.

Description

Technical Field

[0001] This invention relates to the field of metal cutting tool technology, and more particularly to a friction-reducing coating for cutting tools and its preparation method. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Cutting tools, acting as the "teeth" of machining processes, directly impact production efficiency and economic benefits. During cutting, a significant portion of the energy involved in material removal is converted into heat, particularly the substantial frictional heat generated by the intense friction between the chip and the tool's rake face. This heat softens the chip as it passes the rake face, leading to built-up edge formation. Furthermore, the tool-chip contact area on the rake face generates considerable contact pressure during metal cutting, easily causing chipping at the tool tip. Therefore, tool materials must possess high hardness to withstand high temperatures and significant contact pressure. In this field, microtextures or deposited coatings are commonly applied to the tool rake face to reduce friction or improve wear resistance. While microtextures can reduce rake face friction, their wear resistance and hardness still depend on the material properties of the tool itself. Deposited coatings primarily include hard coatings and soft coatings. Hard coatings improve hardness and wear resistance but still generate significant frictional heat, while soft coatings exhibit low wear life due to their lower bonding strength.

[0004] Chinese patent application number 2017102879479 discloses a manufacturing process for a multilayer composite coated cutting tool. It has a multilayer structure and has high hardness, high wear resistance and oxidation resistance. It can slow down the premature peeling of the coating and the propagation of cracks, and significantly improve the overall performance of the coated cutting tool. However, the phenomenon of severe friction in the tool-chip contact area still occurs. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a friction-reducing coating for cutting tools and a preparation method thereof. A hard coating is prepared by intermittent cladding on the tool surface, and a soft coating is prepared by electrohydrodynamic atomization technology between and above the hard coating. The hard coating improves the wear resistance and impact resistance of the cutting tool, while the soft coating reduces friction in the tool-chip contact area, thereby inhibiting the formation of built-up edge.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] The first aspect of the present invention provides a friction-reducing coating for cutting tools, comprising a hard coating layer and a soft coating layer disposed from the inside out. The hard coating layer comprises a plurality of hard coating textures arranged at intervals on the surface of the cutting tool, the length direction of the hard coating textures being perpendicular to the chip friction direction. A soft coating layer is filled between adjacent hard coating textures. The hard coating textures are composed of a hard coating matrix and a reinforcing phase dispersed therein, and the soft coating layer is composed of a lubricating material.

[0008] Optionally, the main material of the hard coating includes one of nickel-based alloys and Co-based alloys.

[0009] Optionally, the reinforcing phase includes one or more of Cr3C2, WC, and TiC.

[0010] Optionally, the material of the lubricating material includes one or more of WS2, MoS2 and graphite.

[0011] Optionally, the hard coating texture is metallurgically bonded to the cutting tool.

[0012] A second aspect of the present invention provides a method for preparing the above-mentioned anti-friction coating for cutting tools, comprising the steps of:

[0013] S1. The hard coating matrix powder and the reinforcing phase powder are ball-milled to obtain a hard coating slurry;

[0014] S2. A hard coating slurry is deposited on the surface of the cutting tool using electrohydrodynamic atomization technology to obtain a slurry layer;

[0015] S3. Using laser micro-cladding technology, melt the slurry layer along a set path to obtain a hard coating texture and remove the unclad slurry layer;

[0016] S4. Lubricating material is deposited on the surface of the cutting tool using electrohydrodynamic atomization technology to obtain a friction-reducing coating for the cutting tool.

[0017] Optionally, in S1, the hard coating matrix powder has a size of 10-20 μm, and the reinforcing phase powder has a size of 200-400 nm.

[0018] Optionally, in S1, the hard coating matrix powder and the reinforcing phase powder are subjected to enhanced ball milling, and then ethyl cellulose and anhydrous ethanol are added for further ball milling to obtain a hard coating slurry.

[0019] Optionally, in S2, in the electrohydrodynamic atomization technology, the slurry flow rate is 9–12 μL, the voltage is 3.5–4.1 kV, the metal nozzle moving speed is 15–30 mm / s, and the nozzle height from the substrate surface is 4–6 mm.

[0020] Optionally, in S3, in the laser micro-cladding technology, nitrogen is used as the protective atmosphere, the laser power is 2-6W, the spot diameter is 15-25μm, the laser scanning speed is 10-20mm / s, and the laser frequency is 10-20kHz.

[0021] Optionally, in S3, the method for removing the uncoated slurry layer is ultrasonic cleaning.

[0022] Optionally, in S4, the lubricant material raw material is a powder with a specification of 1-2 μm.

[0023] Optionally, in S4, the lubricating material, ethyl cellulose, and anhydrous ethanol are mixed evenly to obtain a lubricating material slurry.

[0024] Optionally, in S5, in the electrohydrodynamic atomization technology, the slurry flow rate is 9-12 μL, the voltage is 3.5-4.1 kV, the metal nozzle moving speed is 10-15 mm / s, and the nozzle height from the substrate surface is 4-6 mm.

[0025] The beneficial effects of this invention are as follows:

[0026] 1. The anti-friction coating for cutting tools provided by this invention, due to the deposition of a soft coating material on its outermost surface, can effectively reduce friction during the cutting process, thereby reducing frictional heat generation and inhibiting the formation of built-up edge. Below the soft coating, the soft coating material and the hard coating texture material are spaced apart on the same plane. During friction, the hard coating texture mainly bears the contact pressure and improves the wear resistance of the cutting tool, while the soft coating is squeezed to the friction interface under the contact pressure, thus prolonging the lubrication effect. The anti-friction and wear resistance of the coated cutting tools prepared by this process are significantly enhanced compared to traditional single-coated tools or multi-layered coated tools, resulting in a greatly improved service life.

[0027] 2. This invention uses electrohydrodynamic atomization technology combined with laser micro-cladding technology to prepare hard coating textures, which has lower cost than other processes, higher coating bonding strength, and better wear resistance. It also uses electrohydrodynamic atomization technology to deposit and prepare soft coatings. During the deposition process, the lubricating material first fills the unclad areas between the hard coatings, and then a soft coating of a set thickness is deposited on the surface of the hard and soft coatings, resulting in a longer wear life than other processes. Attached Figure Description

[0028] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0029] The diagram exaggerates the spacing or dimensions between parts to show their positions; the diagram is for illustrative purposes only.

[0030] Figure 1This is a schematic diagram of the anti-friction coating on the cutting tool in Example 1.

[0031] Figure 2 This is a graph showing the test results of the hardness and elastic modulus of the anti-friction coating on the cutting tool in Example 1.

[0032] Figure 3 This is a graph showing the test results of the friction coefficient of the anti-friction coating on the cutting tool in Example 1.

[0033] Among them, 1. Tool substrate; 2. Hard coating texture; 3. Soft coating. Detailed Implementation

[0034] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0035] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0036] A friction-reducing coating for cutting tools includes a hard coating layer and a soft coating layer disposed from the inside out. The hard coating layer includes a plurality of hard coating textures arranged at intervals on the surface of the cutting tool, the length direction of the hard coating textures being perpendicular to the chip friction direction. A soft coating layer is filled between adjacent textures. The hard coating textures are composed of a hard coating matrix and a reinforcing phase dispersed therein, and the soft coating layer is composed of a lubricating material.

[0037] With the above settings, the surface soft coating can effectively reduce cutting heat. The internal soft coating material and hard coating texture material are spaced on the same plane. During the friction process, the hard coating texture mainly bears the contact pressure and improves the wear resistance of the cutting tool, while the soft coating will be squeezed to the friction interface under the contact pressure, thereby prolonging the lubrication effect and greatly improving the tool's service life.

[0038] Optionally, the material of the hard coating substrate includes one of Ni-based alloys and Co-based alloys, specifically Ni60, and may also use most of the raw materials used for spraying.

[0039] Optionally, the reinforcing phase includes one or more of Cr3C2, WC and TiC, which are dispersed in the hard coating matrix to improve impact resistance and wear resistance. The mass ratio of the reinforcing phase to the hard coating matrix is ​​(1-3):(7-9).

[0040] Optionally, the lubricating material may be one or more of WS2, MoS2 and graphite, and may be a common dry lubricant powder.

[0041] Optionally, the cutting tool is one of cemented carbide and alloy steel, which can perform laser cladding on the surface.

[0042] Optionally, the hard coating texture is metallurgically bonded to the cutting tool, the hard coating texture is mechanically bonded to the soft coating, and the soft coating is mechanically bonded to the cutting tool.

[0043] Optionally, the hard coating has an interval of 50-200 μm between adjacent textures, the width of the texture is 50-200 μm and the thickness is 10-30 μm, and the thickness of the soft coating above the texture is 5-10 μm.

[0044] A method for preparing the above-mentioned anti-friction coating for cutting tools includes the following steps:

[0045] S1. The hard coating matrix powder and the reinforcing phase powder are ball-milled to obtain a hard coating slurry;

[0046] S2. A hard coating slurry is deposited on the surface of the cutting tool using electrohydrodynamic atomization technology to obtain a slurry layer;

[0047] S3. Using laser micro-cladding technology, melt the slurry layer along a set path to obtain a hard coating texture and remove the unclad slurry layer;

[0048] S4. Lubricating material is deposited on the surface of the cutting tool using electrohydrodynamic atomization technology to obtain a friction-reducing coating for the cutting tool.

[0049] The method of combining electrohydrodynamic atomization and laser micro-cladding to prepare hard coatings can achieve micron-sized structures and the prepared hard coatings have higher hardness.

[0050] Optionally, in S1, the hard coating matrix powder has a size of 10-20 μm, and the reinforcing phase powder has a size of 200-400 nm.

[0051] Optionally, in S1, the hard coating matrix powder and the reinforcing phase powder are subjected to enhanced ball milling. The particle size of the powder after enhanced ball milling remains unchanged, serving only to achieve uniform mixing. Then, ethyl cellulose and anhydrous ethanol are added and ball milling is continued to achieve uniform mixing, thereby obtaining a hard coating slurry. Ethyl cellulose and anhydrous ethanol are used to prepare a slurry with good dispersion effect to meet the raw material requirements of electrohydrodynamic atomization technology.

[0052] Optionally, in S2, in the electrohydrodynamic atomization technology, the slurry flow rate is 9-12 μL, the voltage is 3.5-4.1 kV, the metal nozzle moving speed is 10-15 mm / s, and the nozzle height from the substrate surface is 4-6 mm, so as to prepare a uniform and dense slurry layer on the tool surface.

[0053] Optionally, in S3, in the laser micro-cladding technology, nitrogen is used as the protective atmosphere, the laser power is 2-6W, the spot diameter is 15-30μm, the laser scanning speed is 10-20mm / s, and the laser frequency is 10-20kHz. The slurry layer within the laser irradiation range is transformed into a molten state and forms a metallurgical bond with the tool surface. According to the planning of the cladding path, a raised hard coating texture is formed on the tool surface.

[0054] Optionally, in S3, the method for removing the uncoated slurry layer is ultrasonic cleaning, which provides space for the deposition of the soft coating and prevents un-laser-irradiated powder from affecting subsequent processing.

[0055] Optionally, in step S4, the lubricating material powder, ethyl cellulose, and anhydrous ethanol are mixed evenly to obtain a lubricating material slurry, wherein the lubricating material powder has a particle size of 1-2 μm.

[0056] Optionally, in S4, in the electrohydrodynamic atomization technology, the slurry flow rate is 9-12 μL, the voltage is 3.5-4.1 kV, the metal nozzle moving speed is 10-15 mm / s, and the nozzle height from the substrate surface is 4-6 mm. During the deposition process, the lubricating material first fills the unmelted areas between the hard coating textures, and then a soft coating of a set thickness is deposited on the surface of the hard and soft coatings, ultimately forming a friction-reducing coating for the cutting tool.

[0057] Example 1

[0058] A friction-reducing coating for cutting tools, such as Figure 1 As shown, cemented carbide YG8 is used as the tool substrate 1. The anti-friction coating of the cutting tool includes a hard coating and a soft coating 3 arranged from the inside to the outside. The hard coating includes multiple hard coating textures 2 arranged at intervals on the surface of the cutting tool. The length direction of the hard coating texture 2 is perpendicular to the chip friction direction. The soft coating 3 fills the gaps between adjacent hard coating textures 2. The composition of the hard coating texture 2 includes the hard coating substrate and the reinforcing phase dispersed therein. The composition of the soft coating 3 includes lubricating material.

[0059] Methods for preparing anti-friction coatings on the surface of cemented carbide cutting tools include:

[0060] Grind and polish the carbide tool substrate, then ultrasonically clean it in an alcohol solution for 20 minutes to remove oil stains.

[0061] Using Ni60 as the self-fluxing powder and Cr3C2 as the reinforcing phase, a Ni60 / Cr3C2 composite powder with a Cr3C2 content of 10% (mass percentage) was prepared. The prepared Ni60 / Cr3C2 composite powder was subjected to enhanced ball milling for 2 hours until it was uniformly mixed. 0.5g of ethyl cellulose and 25g of anhydrous ethanol were added to the ball-milled Ni60 / Cr3C2 composite powder and ball-milled again for 2 hours until it was fully mixed to obtain a hard coating slurry.

[0062] The ball-milled slurry was deposited on the surface of the tool substrate using electrohydrodynamic atomization technology. The slurry flow rate was 9 μL, the voltage was 3.7 kV, the metal nozzle moving speed was 10 mm / s, and the nozzle height from the substrate surface was 5 mm, resulting in a slurry layer with a deposition thickness of 10 μm.

[0063] A laser irradiation area with a width of 100 μm and a spacing of 100 μm was designed in the computer of the laser micro-cladding device. High-purity nitrogen was used as a protective atmosphere to irradiate the laser irradiation area until the powder in the slurry layer melted and formed a metallurgical bond with the tool substrate material. The laser processing was performed once, with a laser power of 6W, a spot diameter of 20 μm, a laser scanning speed of 180 mm / s, and a laser frequency of 20 kHz. Multiple strip-shaped hard coating textures were prepared on the tool surface. The spacing between adjacent hard coating textures was the same as the spacing between the laser irradiation areas, which was 100 μm. The width of the hard coating texture was the same as the width of the laser irradiation area, which was 100 μm, and the height was 10 μm. Afterward, the tool was ultrasonically cleaned in alcohol for 10 min to remove uncoated powder.

[0064] WS2 powder with an average particle size of 1 μm was used as a lubricant. It was mixed with ethyl cellulose and anhydrous ethanol in a ratio of 0.5:0.1:2.5 (mass percentage) and stirred on a magnetic stirrer for 10 h to obtain a soft coating slurry. The soft coating slurry was deposited on the surface of the hard coating and the tool substrate using electrohydrodynamic atomization technology. The electrohydrodynamic atomization parameters were: slurry flow rate of 9 μL, voltage of 3.7 kV, metal nozzle moving speed of 10 mm / s, and nozzle height from the substrate surface of 5 mm. During the deposition process, MoS2 first filled the gaps between the textures of the hard coating, and then a soft coating with a thickness of 5 μm was deposited on the surface of the hard and soft coatings. At this time, the total coating thickness was 15 μm.

[0065] Example 2

[0066] A cutting tool friction-reducing coating, using high-speed steel as the tool substrate, differs from Example 1 in the method of preparing the cutting tool friction-reducing coating on the surface of the high-speed steel tool in that:

[0067] A slurry layer was prepared using Ni60 with a particle size of 10 μm as a self-fluxing powder and Cr3C2 with a particle size of 200 nm as a reinforcing phase.

[0068] In the computer of the laser micro-cladding device, a laser irradiation area with a width of 200 μm and a spacing of 200 μm was designed to prepare a hard coating. During the laser micro-cladding process, the laser power was 4W and the laser scanning speed was 200 mm / s. Multiple strip-shaped hard coating textures were prepared on the surface of the tool. The spacing between adjacent hard coatings was the same as the spacing between the laser irradiation areas, which was 200 μm. The width of the hard coating texture was the same as the width of the laser irradiation area, which was 200 μm.

[0069] A soft coating was prepared using MoS2 powder with a particle size of 1-2 μm as a lubricating material, thereby obtaining a cutting tool friction-reducing coating with a total thickness of 15 μm.

[0070] Test content

[0071] The performance of the anti-friction coating on the cutting tool prepared in Example 1 was tested, and a cemented carbide YG8 tool without an anti-friction coating was used as a control. The test included surface hardness, elastic modulus and coefficient of friction.

[0072] The surface hardness was tested using nanoindentation testing; the elastic modulus was also tested using nanoindentation testing; the results are as follows: Figure 2 As shown, the hardness of the prepared coated tool (Example 1) is increased by 57% and the elastic modulus is increased by 9.6% compared with cemented carbide (YG8).

[0073] Methods for detecting the coefficient of friction include: (friction and wear test); results are as follows: Figure 3 As shown, the coefficient of friction of the coating prepared on the coated tool is significantly lower than that of the cemented carbide tool (YG8), and it maintains a low coefficient of friction of 0.2 during the 30-minute test.

[0074] The advantages of the anti-friction coating for cutting tools provided by this invention are: improved tool hardness and wear resistance; reduced friction coefficient between chips and tool rake face; increased wear life of soft coating material during friction; and secondary lubrication achieved by the soft coating material being extruded to the friction interface under contact pressure during machining.

[0075] The quality of the pre-placed powder layer before laser cladding is also a crucial factor affecting the quality of the cladding layer. Electrohydrodynamic atomization (EHMA) for preparing the pre-placed powder layer allows for controllable thickness preparation, resulting in a uniform powder layer surface free from obvious protrusions or depressions. Furthermore, laser micro-cladding offers the advantage of a smaller spot diameter compared to traditional laser cladding. While the spot diameter of traditional laser cladding lasers is typically on the millimeter scale, the spot diameter of laser micro-cladding lasers is only 20 μm. This allows for a micrometer-scale structure in the cladding layer, leading to superior performance.

[0076] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A friction-reducing coating for cutting tools, characterized in that, It includes a hard coating and a soft coating disposed from the inside out. The hard coating consists of a hard coating matrix and a reinforcing phase dispersed therein, and the soft coating consists of a lubricating material. The hard coating includes multiple textures spaced apart on the surface of the cutting tool, the length direction of which is perpendicular to the chip friction direction; a soft coating is filled between adjacent textures; the lubricating material first fills the unmelted areas between the hard coating textures, and then a soft coating of a set thickness is deposited on the surface of the hard and soft coatings, ultimately forming a friction-reducing coating for the cutting tool.

2. The anti-friction coating for cutting tools according to claim 1, characterized in that, The material of the hard coating substrate includes either a Ni-based alloy or a Co-based alloy.

3. The anti-friction coating for cutting tools according to claim 2, characterized in that, The Ni-based alloy is Ni60.

4. The anti-friction coating for cutting tools according to claim 1, characterized in that, The strengthening phase includes one or more of Cr3C2, WC, and TiC.

5. The anti-friction coating for cutting tools according to claim 1, characterized in that, The lubricating material is made of one or more of WS2, MoS2 and graphite.

6. The anti-friction coating for cutting tools according to claim 1, characterized in that, The hard coating is metallurgically bonded to the cutting tool.

7. The anti-friction coating for cutting tools according to claim 1, characterized in that, The spacing between adjacent textures in the hard coating is 50~200μm, the width of the texture is 50~200μm, the thickness is 10~15μm, and the thickness of the soft coating above the texture is 5~10μm.

8. A method for preparing a friction-reducing coating for cutting tools as described in any one of claims 1-7, characterized in that, Including the following steps: S1. The hard coating matrix powder and the reinforcing phase powder are ball-milled to obtain a hard coating slurry; S2. A hard coating slurry is deposited on the surface of the cutting tool using electrohydrodynamic atomization technology to obtain a slurry layer; S3. Using laser micro-cladding technology, melt the slurry layer along the set path to obtain a hard coating layer and remove the unclad slurry layer; Based on the cladding path planning, a raised hard coating texture is formed on the tool surface; S4. Using electrohydrodynamic atomization technology, lubricating materials are deposited on the surface of the cutting tool to obtain a friction-reducing coating for the cutting tool. During the deposition process, the lubricating material first fills the unmelted areas between the hard coating textures, and then a soft coating of a set thickness is deposited on the surface of the hard and soft coatings.

9. The method for preparing the anti-friction coating for cutting tools according to claim 8, characterized in that, In S1, the hard coating matrix powder has a size of 10~20μm, and the reinforcing phase powder has a size of 200~400nm.

10. The method for preparing the anti-friction coating for cutting tools according to claim 8, characterized in that, In S1, the hard coating matrix powder and the reinforcing phase powder are subjected to enhanced ball milling, and then ethyl cellulose and anhydrous ethanol are added for further ball milling to obtain a hard coating slurry.

11. The method for preparing the anti-friction coating for cutting tools as described in claim 8, characterized in that, In S2, the electrohydrodynamic atomization technology has a slurry flow rate of 9~12μL, a voltage of 3.5~4.1kV, a metal nozzle moving speed of 10~15mm / s, and a nozzle height of 4~6mm from the substrate surface.

12. The method for preparing the anti-friction coating for cutting tools as described in claim 8, characterized in that, In S3, the laser micro-cladding technology uses nitrogen as a protective atmosphere, with a laser power of 15~20W, a spot diameter of 15~25μm, a laser scanning speed of 10~20mm / s, and a laser frequency of 10~30kHz.

13. The method for preparing the anti-friction coating for cutting tools as described in claim 12, characterized in that, The method for removing the uncoated slurry layer is ultrasonic cleaning.

14. The method for preparing the anti-friction coating for cutting tools as described in claim 8, characterized in that, In S4, the raw material for the lubricating material is a powder with a size of 1-2 μm.

15. The method for preparing the anti-friction coating for cutting tools as described in claim 14, characterized in that, In step S4, lubricating material, ethyl cellulose, and anhydrous ethanol are mixed evenly to obtain a lubricating material slurry.

16. The method for preparing the anti-friction coating for cutting tools as described in claim 8, characterized in that, In S4, the electrohydrodynamic atomization technology has a slurry flow rate of 9~12μL, a voltage of 3.5~4.1kV, a metal nozzle moving speed of 10~15mm / s, and a nozzle height of 4~6mm from the substrate surface.

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