A method for preparing a gradient tungsten-based composite coating layer and a cutter prepared by the method

Abstract

The application discloses a preparation method of a gradient tungsten-based composite coating and a cutter prepared by the method. The technical characteristics of a surface mechanical nano-alloying process are used to prepare a gradient tungsten-based composite coating with high nanocrystallization, high hardness and excellent bonding performance on the surface of a base material, and by adding proper titanium powder, tantalum powder and copper powder, the forming capacity, high-temperature performance and heat conduction performance of the coating are improved, and the shortcoming that the surface mechanical nano-alloying process is difficult to prepare a high-performance brittle coating is overcome. Meanwhile, the process introduces two strengthening mechanisms of fine-grain strengthening and solid solution strengthening into the coating, and the hardness and wear resistance of the coating are improved. In addition, in the coating forming process, a three-stage mechanism is adopted to obtain the tungsten-based composite coating with a gradient structure on the surface of the base material, and by adjusting the composition of the mixed powder in each stage, the performance matching degree of the coating is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the preparation technology of gradient tungsten-based alloy coating, in particular to a method for preparing high-performance brittle gradient tungsten-based composite coating and a cutter. BACKGROUND

[0002] In the cutting process, the service life of the cutter will be affected by the cutting temperature and the machining force, and the cutting edge will diffuse and oxidize due to bearing higher cutting temperature, causing the failure of the cutter. After increasing the machining speed and the cutting amount, the cutting efficiency of the workpiece can be significantly improved, but the service life of the cutter will be reduced due to excessive temperature and wear. Since the hard alloy coating has better tribological properties, in order to improve the workpiece machining efficiency and prolong the service life of the cutter, preparing a hard alloy coating on the surface of the cutter becomes an effective improvement technology. The tungsten-based alloy coating has high hardness, compressive strength and good wear resistance, and can almost maintain all physical properties in a higher temperature range, and is stably bonded with the metal substrate, which is a kind of effective high-temperature-resistant hard composite coating to solve the above problems.

[0003] At present, there are many preparation processes of tungsten-based composite coating, and the main processes widely used for the preparation of cutter surface coating are CVD, PVD, thermal spraying, vacuum sintering and the like. However, the above-mentioned preparation methods of tungsten-based composite coating have some disadvantages, such as the coating obtained by PVD process is thin (micron-level coating) and has poor interface bonding capacity; the deposition rate of CVD process is low, the waste gas treatment is difficult and the cost is high; the coating obtained by thermal spraying process has poor compactness and impurities are easily mixed in the spraying process; the coating obtained by vacuum sintering has high cost and is not environmentally friendly.

[0004] The mechanical alloying method has the characteristics of simple treatment process, easy control and low cost, but the mechanical alloying process is used for the treatment of the surface of the substrate, and there are few literatures about the use of the surface mechanical alloying process for the treatment of tungsten-based coating. Some literatures are only used for powder pre-alloying treatment process, such as CN115341112A and CN101880808A.

[0005] At the same time, the design of the coating structure also has an important influence on its comprehensive performance. The coating with single-layer structure often fails prematurely due to the large gap between the coating and the substrate. Therefore, designing a gradient coating with double-layer or multi-layer structure is of great significance to solve the above problems. However, how to reasonably design the composition of each layer is the key to preparing the gradient coating. SUMMARY

[0006] The present application aims to solve the prior art: the existing tungsten-based coating process technology has high cost, poor density, small thickness, and is not environmentally friendly, and the single-layer structure coating often fails prematurely due to the large performance gap with the substrate, and therefore a method for preparing a high-performance brittle gradient tungsten-based composite coating is proposed.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0008] A preparation method of a gradient tungsten-based composite coating, comprising the following preparation steps:

[0009] 2) Coating powder pretreatment: different component ratios of tungsten-based mixed powder are loaded into a ball mill tank, protective gas is filled, and high-energy ball milling is used for 1h-5h of powder mixing treatment to fully mix the powder;

[0010] Among them, the tungsten-based mixed powder components include tungsten, titanium, tantalum, and copper;

[0011] 3) Gradient tungsten-based composite coating preparation:

[0012] Initial stage: a certain amount of mixed powder with low tungsten content is weighed and uniformly mixed, the content of tungsten powder in the mixed powder is at least 40wt.%, a suitable ball-to-material ratio is selected, and then it is loaded into a ball mill tank together with the substrate and tungsten carbide balls for 0.5h-2h of surface mechanical nanocrystallization treatment, thereby obtaining a hard tungsten-based composite coating on the surface of the substrate;

[0013] Cyclic stage: the content of tungsten powder in the mixed powder is gradually increased, the content of titanium powder in the mixed powder is gradually reduced, and the surface mechanical nanocrystallization treatment is repeatedly performed in multiple times to obtain a tungsten-based composite coating with gradient distribution of components and relatively thick thickness;

[0014] Final stage: high-tungsten-content mixed powder is used for surface mechanical nanocrystallization treatment, and the content of tungsten powder in the mixed powder is at least 80wt.%, thereby obtaining a highly nanocrystallized and densified tungsten-based composite coating.

[0015] Preferably, in the step 2), tungsten: titanium: tantalum: copper = (4-9):(1-3):(0-2):(0-1), the mixed powder shape is selected to be spherical or spherical-like, and the powder particle size distribution is (15μm-25μm):(5μm-15μm):(<5μm) = (5-10):(0-2):(0-3).

[0016] Preferably, in the step 3), the content of tungsten powder in the mixed powder in the initial stage is 40wt.%-60wt.%, the content of titanium powder is 20wt.%-30wt.%, the content of tantalum powder is 0wt.%-20wt.%, and the content of copper powder is 0wt.%-10wt.%.

[0017] Preferably, in the step 3), the content of tungsten powder in the mixed powder in the circulation stage is 50wt.%-70wt.%, the content of titanium powder is 10wt.%-20wt.%, the content of tantalum powder is 0wt.%-20wt.%, and the content of copper powder is 0wt.%-10wt.%.

[0018] Preferably, in the step 3), the content of tungsten powder in the mixed powder in the final stage is 60wt.%-90wt.%, the content of titanium powder is 0wt.%-10wt.%, the content of tantalum powder is 0wt.%-20wt.%, and the content of copper powder is 0wt.%-10wt.%.

[0019] Preferably, in the steps 2) and 3), the powder mixing and preparation process is a high-speed "∞" type three-dimensional motion mechanism, and high-purity argon is selected as the protective atmosphere.

[0020] Preferably, in the step 3), the related process parameters for preparing the gradient tungsten-based composite coating by the surface mechanical nano-alloying process are as follows: high-purity argon is selected as the environmental atmosphere, 30-50 tungsten carbide balls with a diameter of 6mm are selected as the ball milling medium, the ball-to-powder ratio is set to (16-5):1, and the rotation speed of the ball mill is 1725r / min.

[0021] Preferably, the step 2) further comprises:

[0022] 1) Surface pretreatment of the base material: the surface of the workpiece material is subjected to grinding and polishing pretreatment, and is ultrasonically cleaned in anhydrous ethanol and acetone solution for 10min, respectively, and then is blown dry to obtain a base material with low surface roughness and smoothness.

[0023] Preferably, in the step 1), the surface of the base material is polished by #320, #600, #800, and #1500 grit sandpaper, and then is polished by 2.5μm and 0.5μm diamond, so as to finally obtain a smooth and low-roughness base material surface.

[0024] A cutter comprises a cutter material and a coating prepared by the method for preparing a gradient tungsten-based composite coating according to any one of claims 1 to 9.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] The application utilizes the technical features of the surface mechanical nanocrystallization process to prepare a gradient tungsten-based composite coating with high nanocrystallization, high hardness and excellent bonding performance on the surface of a substrate, and by adding appropriate amounts of titanium powder, tantalum powder and copper powder, the forming ability, high-temperature performance and thermal conductivity of the coating are improved, overcoming the shortcomings of the surface mechanical nanocrystallization process in that it is difficult to prepare a high-performance brittle coating. At the same time, the process introduces two strengthening mechanisms of fine-grain strengthening and solid solution strengthening in the coating, improving the hardness and wear resistance of the coating. In addition, during the formation of the coating, a three-stage mechanism is adopted to obtain a tungsten-based composite coating with a gradient structure on the surface of the substrate, and by adjusting the composition of the mixed powder in each stage, the matching degree of various performances of the coating is improved. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a cross-sectional SEM image of the initial stage tungsten-based composite coating.

[0028] Figure 2 is a hardness distribution diagram of the gradient tungsten-based composite coating. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application.

[0030] Embodiment 1

[0031] A preparation method of a gradient tungsten-based composite coating is performed according to the following steps:

[0032] 1) Surface pretreatment of the substrate material: the surface of the workpiece material is polished by multiple passes of sandpaper #320, #600, #800, #1500, etc., and then polished by 2.5 μm and 0.5 μm diamond to obtain a surface with low roughness, followed by ultrasonic cleaning in anhydrous ethanol and acetone solution for 10 min and blowing dry, finally obtaining a substrate with low surface roughness and cleanliness;

[0033] 2) Coating powder pretreatment: three different tungsten-based mixed powders were weighed, with specific component ratios as follows: ① 60wt.% tungsten powder, 30wt.% titanium powder, 5wt.% tantalum powder, 5wt.% copper powder; ② 65wt.% tungsten powder, 20wt.% titanium powder, 5wt.% tantalum powder, 10wt.% copper powder; ③ 75wt.% tungsten powder, 5wt.% titanium powder, 10wt.% tantalum powder, 10wt.% copper powder. The three kinds of tungsten-based mixed powders with different component ratios were respectively loaded into a ball mill tank, high-purity argon was filled as a protective gas, and high-energy ball milling was used for 2h of powder mixing treatment to fully mix the powders and avoid uneven composition during coating formation. Among them, ① is used for initial stage coating preparation, at this time the tungsten content is the lowest and the titanium content is the highest, which can effectively improve the coating formation ability and coating quality; ② is used for cyclic stage coating preparation, at this time the tungsten powder and copper powder content is gradually increased, the titanium powder content is reduced, and the tantalum powder content is maintained unchanged, so as to ensure the heat conduction performance of the coating in the cycle stage; ③ is used for the final stage of coating preparation, at this time the tungsten powder and tantalum powder content is continuously increased, to maintain the high hardness, wear resistance and high temperature performance of the surface layer.

[0034] 3) Gradient tungsten-based composite coating preparation: 4g of uniformly mixed powder ① is weighed, the ball-to-powder ratio is 8:1, then it is loaded into a ball mill tank with the substrate and 40 tungsten carbide balls for 1h of surface mechanical nanocrystallization treatment, and the tungsten carbide balls can prevent the introduction of impurities, so that a uniform, dense and about 80μm thick hard tungsten-based composite coating can be obtained on the surface of the substrate, as shown in Figure 1The applicant initially used common tungsten-based alloy coating technology in the research, namely CVD, PVD and thermal spraying, vacuum sintering and other process methods, but the cost was high and the thickness was micron level. Since the tool surface layer needs to have a long service life under the condition of high machining speed and cutting amount, the applicant found by chance that a high-performance brittle coating layer can be formed on the surface of the surface substrate by using surface mechanical nanocrystallization treatment on the tungsten-based alloy. Similarly, the coating layer can only obtain micron-level thickness. Secondly, since most tungsten-based alloy powders use tungsten and tantalum, the continuity is poor and the coating patch is easy to appear. After continuous experiments, the tungsten-based alloy coating layer with large thickness, uniform density and good continuity is finally obtained. The tungsten-based alloy coating layer has excellent formability, high-temperature performance and thermal conductivity. Since the titanium powder is a soft and hard powder compared with the tungsten powder and the tantalum powder, the titanium powder plays a role of a sparse component in the coating layer, so that the coating layer composition is uniform, and the titanium powder also acts as a binder between the two, so that the coating layer is more dense. The introduction of the titanium powder can also overcome the poor property of tungsten and copper, so as to ensure that the tungsten alloy coating layer has high density, high thermal conductivity and small thermal expansion coefficient. In the circulation stage, 4g of uniformly mixed powder ② is weighed, and surface mechanical nanocrystallization treatment is sequentially performed for 1h, so as to obtain a gradient coating layer with good hardness distribution and high mechanical property matching degree, as shown in Figure 2 The gradient interlayer structure can be obtained, but the interlayer interface does not appear; in the final stage, the powder ③ with high tungsten content is used for surface mechanical nanocrystallization treatment for 3h, so as to obtain a gradient tungsten-based composite coating layer with high nanocrystallization, high hardness and high wear resistance.

[0035] Example 2

[0036] A preparation method of a gradient tungsten-based composite coating layer is performed according to the following steps:

[0037] 1) Surface pretreatment of the base material: the surface of the workpiece material is polished by #320, #600, #800, #1500 and other multiple passes of sandpaper, and then polished by 2.5μm and 0.5μm diamond to obtain a surface with low roughness. Then, ultrasonic cleaning is performed in anhydrous ethanol and acetone solution for 10min and then dried, so as to obtain a base material with low surface roughness and cleanliness;

[0038] 2) Coating powder pretreatment: Five different tungsten-based mixed powders were weighed, with specific component ratios as follows: ① 55wt.% tungsten powder, 30wt.% titanium powder, 10wt.% tantalum powder, 5wt.% copper powder; ② 60wt.% tungsten powder, 25wt.% titanium powder, 10wt.% tantalum powder, 5wt.% copper powder; ③ 65wt.% tungsten powder, 20wt.% titanium powder, 10wt.% tantalum powder, 5wt.% copper powder; ④ 70wt.% tungsten powder, 15wt.% titanium powder, 10wt.% tantalum powder, 5wt.% copper powder; ⑤ 75wt.% tungsten powder, 10wt.% titanium powder, 10wt.% tantalum powder, 5wt.% copper powder. The five kinds of tungsten-based mixed powders with different component ratios were respectively loaded into a ball mill tank, high-purity argon was filled as protective gas, and high-energy ball milling was used for 2h of powder mixing treatment to fully mix the powders and avoid the formation of composition inhomogeneity during the coating formation process. Among them, one kind of mixed powder in the cycle stage of Example 1 was increased to three kinds, ②, ③, ④, the tungsten powder content was increased by 5wt.% in turn, while the titanium powder content was reduced by 5wt.% in turn, and the tantalum powder and copper powder contents were maintained unchanged, so as to ensure that the coating has a more gentle composition gradient and improves the performance matching degree with the front and rear two-stage coatings.

[0039] (3) Gradient tungsten-based composite coating preparation: 4g of uniformly mixed powder ① was weighed for the initial stage, the ball powder ratio was 8:1, then it was loaded into a ball mill tank together with the substrate and 40 tungsten carbide balls for 1h of surface mechanical nanocrystallization treatment, and then a uniform and dense hard tungsten-based composite coating was obtained on the surface of the substrate; 4g of uniformly mixed powders ②, ③, ④ were respectively weighed for the cycle stage, and 1h of surface mechanical nanocrystallization treatment was carried out in turn to obtain a gradient coating with good hardness distribution and high mechanical performance matching degree; 3h of surface mechanical nanocrystallization treatment was carried out using high-tungsten-content powder ⑤ in the final stage to obtain a gradient tungsten-based composite coating with high nanocrystallization, high hardness and high wear resistance.

[0040] Example 3

[0041] A method for preparing a gradient tungsten-based composite coating, which is carried out according to the following steps:

[0042] 1) Surface pretreatment of the substrate material: The surface of the workpiece material was polished by multiple passes of sandpaper #320, #600, #800, #1500, etc., and then polished by 2.5μm and 0.5μm diamond to obtain a surface with low roughness. Then the surface was ultrasonically cleaned in anhydrous ethanol and acetone solution for 10min and dried to obtain a substrate with low surface roughness and cleanliness;

[0043] 2) Coating powder pretreatment: five different component tungsten-based mixed powders were weighed, with specific component ratios as follows: ① 55wt.% tungsten powder, 30wt.% titanium powder, 10wt.% tantalum powder, 5wt.% copper powder; ② 60wt.% tungsten powder, 25wt.% titanium powder, 10wt.% tantalum powder, 5wt.% copper powder; ③ 65wt.% tungsten powder, 20wt.% titanium powder, 10wt.% tantalum powder, 5wt.% copper powder; ④ 70wt.% tungsten powder, 15wt.% titanium powder, 10wt.% tantalum powder, 5wt.% copper powder; ⑤ 75wt.% tungsten powder, 5wt.% titanium powder, 10wt.% tantalum powder, 10wt.% copper powder. The five kinds of tungsten-based mixed powders with different component ratios were respectively loaded into a ball mill tank, high-purity argon was filled as protective gas, and high-energy ball milling was performed for 5h to improve the mixing powder time, make the components of each layer of original powder more uniform, avoid the performance difference of each layer caused by uneven components, and shorten the service life of the tool. Among them, ① is used for initial stage coating preparation, at this time the tungsten content is the lowest and the titanium content is the highest, which can effectively improve the coating forming ability and coating quality; ②, ③, ④ are used for coating preparation in the circulation stage, at this time the tungsten powder content is gradually increased, the titanium powder content is reduced, and the tantalum powder and copper powder contents are maintained unchanged, so as to ensure the high temperature performance and thermal conductivity of the outer coating; ⑤ is used for coating preparation in the final stage, at this time the tungsten powder and copper powder contents are further increased, and the surface layer maintains high hardness, wear resistance and thermal conductivity.

[0044] (3) Gradient tungsten-based composite coating preparation: 4g of uniformly mixed powder ① was weighed in the initial stage, the ball powder ratio was 8:1, and then it was loaded into a ball mill tank together with the substrate and 40 tungsten carbide balls. The surface mechanical nanocrystallization treatment time was shortened to 0.5h. During the surface mechanical nanocrystallization process, the powder usually completes the powder accumulation in a short time, forming a coating with high density. Therefore, shortening the treatment time in the initial stage can avoid coating fatigue and affect the subsequent powder stacking; 4g of uniformly mixed powders ②, ③, ④ were respectively weighed in the circulation stage, and 0.5h of surface mechanical nanocrystallization treatment was performed in turn. Reducing the treatment time in this stage is still for the smooth formation of the subsequent coating; 5h of surface mechanical nanocrystallization treatment was performed in the final stage using high-tungsten-content powder ⑤. Increasing the surface mechanical nanocrystallization treatment time in the final stage can promote the solid solution degree between elements and enhance the nanocrystallization degree of the coating. Therefore, the gradient tungsten-based composite coating obtained has higher hardness and wear resistance.

[0045] Example 4

[0046] A tool comprising a tool material and a coating prepared on the surface of the tool material by the gradient tungsten-based composite coating preparation method described in the examples.

[0047] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto. The alternatives can be partial structure, device, method step alternatives, or complete technical solutions. According to the technical solutions of the present application and the inventive concept, equivalent replacement or change should be covered within the protection scope of the present application.

Claims

1. A method for producing a gradient tungsten-based composite coating, characterized by, The preparation steps include: 1) Coating powder pretreatment: the tungsten-based mixed powder with different component proportions is loaded into a ball mill tank, a protective gas is filled, and a high-energy ball mill is used for 1-5 h of powder mixing treatment to fully mix the powder; wherein the tungsten-based mixed powder components are tungsten, titanium, tantalum, and copper; 2) Gradient tungsten-based composite coating preparation: Initial stage: a certain amount of mixed powder with low tungsten content is weighed and uniformly mixed, a suitable ball-to-powder ratio is selected, and then it is loaded into a ball mill tank together with the substrate and tungsten carbide balls for 0.5-2 h of surface mechanical nanocrystallization treatment, thereby preliminarily obtaining a hard tungsten-based composite coating on the substrate surface; Cyclic stage: the tungsten powder content in the mixed powder is gradually increased, and the titanium powder content in the mixed powder is gradually reduced, and the surface mechanical nanocrystallization treatment is repeatedly performed in multiple times to obtain a tungsten-based composite coating with gradient distribution of components and relatively thick thickness; Final stage: high-tungsten-content mixed powder is used for surface mechanical nanocrystallization treatment to obtain a highly nanocrystallized and densified tungsten-based composite coating; In the initial stage of step 2), the tungsten powder content in the mixed powder is 40-60 wt.%, the titanium powder content is 20-30 wt.%, the tantalum powder content is 10-20 wt.%, and the copper powder content is 5-10 wt.%; In the cyclic stage, the tungsten powder content in the mixed powder is 60-70 wt.%, the titanium powder content is 10-20 wt.%, the tantalum powder content is 10-20 wt.%, and the copper powder content is 5-10 wt.%; In the final stage, the tungsten powder content in the mixed powder is 70-75 wt.%, the titanium powder content is 5-10 wt.%, the tantalum powder content is 10 wt.%, and the copper powder content is 10 wt.%.

2. The method of claim 1, wherein the gradient tungsten-based composite coating is prepared by a process comprising: In steps 1) and 2), the powder mixing and preparation process is a high-speed "∞" type three-dimensional motion mechanism, and high-purity argon gas is selected as the protective atmosphere.

3. The method of claim 1, wherein the gradient tungsten-based composite coating is prepared by a process comprising: In step 2), the related process parameters for preparing the gradient tungsten-based composite coating by surface mechanical nanocrystallization process are as follows: high-purity argon gas is used as the environmental atmosphere, 30-50 tungsten carbide balls with a diameter of 6 mm are selected as the ball milling medium, the ball-to-powder ratio is set to (16-5):1, and the rotation speed of the ball mill is 1725 rpm.

4. The method of claim 1, wherein the gradient tungsten-based composite coating is prepared by a process comprising: Before step 1), it further includes: Substrate material surface pretreatment: the workpiece material surface is ground and polished for pretreatment, ultrasonic cleaning in anhydrous ethanol and acetone solution for 10 min respectively, and then dried to obtain a substrate with low surface roughness and smoothness.

5. The method of claim 4, wherein the gradient tungsten-based composite coating is prepared by a process comprising: In the substrate material surface pretreatment, the substrate surface is polished with #320, #600, #800, and #1500 sandpaper, and then polished with 2.5 μm and 0.5 μm diamond, to finally obtain a smooth and low-roughness substrate surface.

6. A cutting tool characterized by A tool material and a coating prepared on the surface of the tool material by the gradient tungsten-based composite coating preparation method of any one of claims 1-5.

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