Pretreatment method for cemented carbide substrate of CVD diamond coating

Abstract

The cemented carbide substrate composite pretreatment method of the CVD diamond coating has two methods. The process steps of the first method are as follows: (1) acid-base two-step chemical etching treatment, (2) heat treatment. The process steps of the second method are as follows: (1) acid-base two-step chemical etching treatment, (2) filling of refractory metal powder or refractory metal carbide powder, (3) heat treatment. The first method solidifies the loose surface layer of the cemented carbide substrate after chemical etching through heat treatment, blocks the communication holes left by Co etching with the internal substrate, and improves the firmness of the surface layer WC grains. The second method fills the Co-removed cemented carbide substrate surface layer cavities and internal communication pores with refractory metal powder or refractory metal carbide powder, and then solid-phase sintering through heat treatment to form a relatively dense carbide surface layer and a roughened surface. Thus, both methods can improve the adhesion of the diamond coating.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of cemented carbide processing, and particularly relates to a pretreatment method for a cemented carbide substrate of a CVD (chemical vapor deposition) diamond-coated tool. BACKGROUND

[0002] CVD diamond coating (film) is a crystal formed by carbon-carbon covalent bonds in sp 3 hybrid form, which is very close to natural diamond in properties, and has high hardness, high thermal conductivity, low friction coefficient, low thermal expansion coefficient, and good self-lubricity and chemical stability, and is an ideal tool material. In particular, diamond-coated tools can be directly deposited on complex-shaped tool substrates, and have great advantages in cutting processing of non-ferrous metals and alloys, metal matrix composites, engineering ceramics, and fiber-reinforced composites.

[0003] The service performance of a diamond-coated tool mainly depends on three aspects of tool substrate performance, coating quality, and use environment. Among them, the physicochemical properties of the substrate material have a direct impact on the nucleation, growth, morphology, and even structure of diamond, and the film-substrate adhesion (bonding strength, adhesion).

[0004] WC-Co cemented carbide is the most widely used and best comprehensive performance diamond-coated tool substrate material at present. However, due to the presence of Co and the difference in thermal expansion coefficient between the cemented carbide substrate and the diamond film, the adhesion of the diamond coating on the WC-Co cemented carbide substrate is not high, which seriously limits its application. Therefore, how to improve the adhesion of the diamond coating on the cemented carbide substrate is a key problem in related research.

[0005] Regarding how to improve the adhesion of the diamond coating on the WC-Co cemented carbide substrate, the prior art discloses a two-step acid-base chemical etching technical solution for pretreating the cemented carbide substrate (such as US5236740), that is, after cleaning the cemented carbide substrate, etching it with alkali solution and then etching it with acid solution to remove Co on the surface layer of the cemented carbide substrate. However, the removal of Co on the surface layer of the substrate will leave voids and form loose structures, and the WC grains on the surface layer will lose the bonding effect of Co and only rely on the bonding force of the WC grains in the subsurface layer, which is extremely easy to fall off. The bonding strength of the CVD diamond coating and the cemented carbide substrate after chemical etching is still insufficient, and the CVD diamond-coated cemented carbide tool still cannot meet the use requirements in high-demand fields such as aviation carbon fiber composites and ceramic part processing. SUMMARY

[0006] The present application aims to overcome the deficiencies of the prior art, and provides a composite pretreatment method for a cemented carbide substrate of a CVD diamond coating, so as to improve the adhesion of a WC-Co high hardness cemented carbide substrate to a CVD diamond coating and improve the quality of the deposited diamond coating.

[0007] The composite pretreatment method for a cemented carbide substrate of a CVD diamond coating according to the present application has two technical solutions (methods) belonging to one general inventive concept.

[0008] 1. A first composite pretreatment method for a cemented carbide substrate

[0009] The process steps of the composite pretreatment method are as follows in sequence:

[0010] (1) Two-step chemical etching treatment of acid and alkali

[0011] After the cemented carbide substrate of the CVD diamond coating is cleaned to remove surface impurities, the substrate is first etched with an alkali solution, then etched with an acid solution, and then cleaned to remove the acid and alkali substances, thereby obtaining a cemented carbide substrate treated by acid and alkali etching;

[0012] (2) Heat treatment

[0013] The cemented carbide substrate treated by acid and alkali etching is heated to 1000-1300°C under vacuum or under hydrogen protection or under inert gas protection for 0.5-2h, and then cooled to room temperature in the furnace, and then cleaned to remove surface impurities and dried, thereby completing the pretreatment of the cemented carbide substrate of the CVD diamond coating.

[0014] In the above method, the alkali solution (Murakami reagent) is prepared from KOH, K3[Fe(CN)6] and deionized water, and the mass ratio of KOH, K3[Fe(CN)6] and deionized water is 1:1:10, and the alkali etching is performed by immersing the cemented carbide substrate in the alkali solution for 10-30min in an ultrasonic bath; the acid solution (Caro acid) is prepared from H2SO4 and H2O2, and the volume ratio of H2SO4 and H2O2 is 1:10, and the acid etching is performed by immersing the cemented carbide substrate in the acid solution for 10-30s in an ultrasonic bath.

[0015] In the above method, the cleaning of the cemented carbide substrate in steps (1) and (2) is first performed by ultrasonic cleaning with anhydrous ethanol, and then performed by ultrasonic cleaning with deionized water.

[0016] In the above method, the vacuum condition in step (2) refers to a vacuum degree of ≤30Pa, and the inert gas is argon or nitrogen.

[0017] 2. A second composite pretreatment method for a cemented carbide substrate

[0018] The process steps of the composite pretreatment method are as follows in sequence:

[0019] (1) Acid-base two-step chemical corrosion treatment

[0020] After the CVD diamond-coated cemented carbide substrate is cleaned to remove surface impurities, the substrate is first etched with alkali solution, then etched with acid solution, and then cleaned to remove the acid and alkali substances, thereby obtaining an acid-alkali etched cemented carbide substrate;

[0021] (2) Filling of refractory metal powder or refractory metal carbide powder

[0022] The acid-alkali etched cemented carbide substrate is immersed in a suspension of refractory metal powder or refractory metal carbide powder for 1-10 minutes in an ultrasonic bath, and then dried, thereby obtaining a cemented carbide substrate filled with refractory metal powder or refractory metal carbide powder; the suspension of refractory metal powder or refractory metal carbide powder is prepared by adding 10 g of refractory metal powder or refractory metal carbide powder, 0.5-1 g of paraffin wax, and 0.5-1 g of surfactant to 100 mL of hexane and stirring until uniform;

[0023] (3) Heat treatment

[0024] The cemented carbide substrate filled with refractory metal or metal carbide powder is heated to 1000-1300°C under vacuum or under hydrogen protection or under inert gas protection for 0.5-2 hours, and then cooled to room temperature in the furnace, after which the surface impurities are removed by cleaning and the substrate is dried, thereby completing the pretreatment of the CVD diamond-coated cemented carbide substrate.

[0025] In the above method, the refractory metal in step (2) is at least one of W, Mo, and Cr, and the refractory metal carbide is at least one of WC, Mo2C, and Cr3C2; the surfactant is zinc stearate (C 36 H 70 O4Zn) or / and isomyl (bis(2-hydroxyethyl)oleylamine, C 22 H 45 NO2), and when the surfactant is zinc stearate and isomyl, the mass ratio of zinc stearate to isomyl is 1:1.

[0026] In the above method, the refractory metal powder or refractory metal carbide powder in step (2) has a Fisher particle size (FSSS) of ≤0.8 μm.

[0027] In the above method, the alkali solution (Murakami reagent) in step (1) is prepared by KOH, K3[Fe(CN)6] and deionized water with a mass ratio of KOH:K3[Fe(CN)6]:deionized water=1:1:10, and the alkali solution corrosion is to immerse the cemented carbide substrate in the alkali solution for 10-30 minutes in an ultrasonic bath; the acid solution (Caro acid) is prepared by H2SO4 and H2O2 with a volume ratio of H2SO4:H2O2=1:10, and the acid solution corrosion is to immerse the cemented carbide substrate in the acid solution for 10-30 seconds in an ultrasonic bath.

[0028] In the above method, the cleaning of the cemented carbide substrate in step (1) and step (3) is first ultrasonic cleaning with anhydrous ethanol, and then ultrasonic cleaning with deionized water.

[0029] In the above method, the vacuum condition in step (3) refers to a vacuum degree ≤30 Pa, and the inert gas is argon or nitrogen.

[0030] Compared with the prior art, the method has the following beneficial technical effects:

[0031] (1) The first method of the present application first removes Co on the surface layer of the WC-Co cemented carbide substrate by the two-step acid-alkali chemical corrosion, and then solidifies the loose surface layer of the cemented carbide substrate after chemical corrosion by heat treatment, and blocks the communication holes with the inside of the cemented carbide substrate left by Co removal, and at the same time improves the firmness of the surface layer WC grains, thereby effectively improving the bonding strength between the WC-Co cemented carbide substrate and the CVD diamond coating (see the examples). Since the surface layer of the cemented carbide substrate is solidified after heat treatment, the firmness of the surface layer WC grains is improved, and thus the quality of the deposited diamond coating can be improved.

[0032] (2) The second method of the present application first removes Co on the surface layer of the WC-Co cemented carbide substrate by the two-step acid-alkali chemical corrosion, and then fills the Co-removed surface layer cavities and the pores communicated with the inside of the cemented carbide substrate with refractory metal powder or refractory metal carbide powder, and then forms a relatively dense carbide surface layer and a roughened surface by solid phase sintering through heat treatment, thereby improving the bonding strength between the WC-Co cemented carbide substrate and the CVD diamond coating (see the examples), and the quality of the diamond coating deposited on the cemented carbide substrate is better.

[0033] (3) The method of the present application optimizes the temperature and holding time of heat treatment, thereby ensuring the above-mentioned effects of heat treatment and avoiding the melting of Co in the inside of the cemented carbide substrate to form a liquid phase and migrate and transfer to the surface layer.

[0034] The method of the present application is not only suitable for the pretreatment of WC-Co high hardness cemented carbide substrate, but also applicable to the pretreatment of other cemented carbide substrates. Attached Figure Description

[0035] Figure 1 This is a SEM image of the indentation from the adhesion test of the diamond coating on the cemented carbide substrate in Comparative Example 1.

[0036] Figure 2 This is a SEM image of the indentation from the adhesion test of the diamond coating on the cemented carbide substrate in Example 3. Detailed Implementation

[0037] The pretreatment method for cemented carbide substrate composite with CVD diamond coating according to the present invention will be further described below with reference to the accompanying drawings and examples. Obviously, the described examples are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0038] In the following examples and comparative examples, the reagents used were analytical grade. The H2SO4 used to prepare the Caro acid solution was concentrated sulfuric acid (95%–98% by mass), and the H2O2 was a 30% H2O2 solution. Unless otherwise specified, all reagents and instruments used were commercially available and readily available products. Where specific conditions are not specified, they were performed under standard conditions or conditions recommended by the manufacturer.

[0039] In the following examples and comparative examples, the adhesion (bonding strength between coating and substrate) of diamond coatings on cemented carbide substrates was evaluated using the HRC indentation method according to the literature “N.,V.,AAand BN (2003). The VDI3198 indentation test evaluation of a reliable qualitative control for layered compounds.”Journal of Materials Processing Tech,143(1):481-485.”. HF1 was the best and HF6 was the worst.

[0040] Examples 1-6 and Comparative Example 1

[0041] Examples 1-6 and Comparative Example 1 all used WC-6Co(YG6X) cemented carbide as the substrate for CVD diamond coating.

[0042] 1. The process steps for the composite pretreatment of the cemented carbide matrix in Example 1 are as follows:

[0043] (1) Two-step acid-base chemical corrosion treatment

[0044] The WC-6Co (YG6X) cemented carbide substrate was immersed in anhydrous ethanol for ultrasonic cleaning for 10 min, and then immersed in deionized water for ultrasonic cleaning for 5 min to remove surface impurities;

[0045] The cleaned cemented carbide substrate was immersed in an alkaline solution (Murakami reagent) for ultrasonic bath for 30 min, the alkaline solution was prepared by KOH, K3[Fe(CN)6] and deionized water, and the mass ratio of KOH: K3[Fe(CN)6]: deionized water was 1:1:10; the alkaline-etched cemented carbide substrate was immersed in an acid solution (Caro acid) for ultrasonic bath for 15 s, the acid solution was prepared by H2SO4 and H2O2, and the volume ratio of H2SO4: H2O2 was 1:10;

[0046] The etched cemented carbide substrate was immersed in anhydrous ethanol for ultrasonic cleaning for 10 min, and then immersed in deionized water for ultrasonic cleaning for 5 min to remove acid and alkaline substances;

[0047] (2) Heat treatment

[0048] The cemented carbide substrate treated by step (1) was placed in a vacuum furnace, vacuumized and controlled the vacuum degree in the furnace to be ≤30 Pa, and heated to 1300 ℃ at a heating rate of 1 ℃-2 ℃ / h, and kept for 0.5 h, then powered off after the end of keeping, and cooled to room temperature with the furnace, then the cemented carbide substrate was immersed in anhydrous ethanol for ultrasonic cleaning for 10 min, and then immersed in deionized water for ultrasonic cleaning for 5 min to remove surface impurities, and then placed in an oven for drying at 50 ℃, and the pretreatment of the cemented carbide substrate was completed.

[0049] 2. The process steps of the composite pretreatment of the cemented carbide substrate in Example 2-6 are as follows:

[0050] (1) Two-step chemical etching treatment of acid and alkali

[0051] The operation and process parameters were the same as those in Example 1;

[0052] (2) Filling of refractory metal powder or refractory metal carbide powder

[0053] The W powder in Example 2 was FSSS particle size 0.23 μm, the WC powder in Example 3 was FSSS particle size 0.28 μm, the Mo powder in Example 4 was FSSS particle size 0.32 μm, the Cr powder in Example 5 was FSSS particle size 0.82 μm, and the Cr3C2 powder in Example 6 was FSSS particle size 0.67 μm;

[0054] The cemented carbide substrate of each example treated by step (1) acid-base chemical etching was immersed into the corresponding suspension of refractory metal powder or refractory metal carbide powder for 10 minutes in an ultrasonic bath, and then was placed into an oven for drying at 50°C, thus obtaining the cemented carbide substrate filled with refractory metal powder or refractory metal carbide powder of each example. The suspension of refractory metal powder or refractory metal carbide powder of each example was prepared as follows: 10 g of refractory metal powder or refractory metal carbide powder, 0.5 g of paraffin, 0.5 g of zinc stearate and 0.5 g of isopar M were added into 100 mL of hexane, and then the mixture was stirred uniformly;

[0055] (3) Heat treatment

[0056] The cemented carbide substrate filled with refractory metal or metal carbide powder of step (2) was placed into a vacuum furnace for heat treatment, and the operation and process parameters of the heat treatment were the same as those of Example 1.

[0057] 3. Pretreatment of the cemented carbide substrate of Comparative Example 1

[0058] The pretreatment of the cemented carbide substrate of Comparative Example 1 was only acid-base two-step chemical etching treatment, and the operation and process parameters were the same as those of Example 1.

[0059] 4. Deposition of diamond coating on the pretreated cemented carbide substrate of Examples 1-6 and Comparative Example 1

[0060] The pretreated cemented carbide substrate of each example and Comparative Example was subjected to diamond coating deposition by hot filament chemical vapor deposition (HF-CVD), and the process parameters were as follows: 9 Ta hot filaments, the interval between each Ta hot filament was 20 mm, the distance between the cemented carbide substrate and the Ta hot filament was 10 mm, the power was 7200 W, CH4 / H2=2.5 / 100 (flow ratio), the total gas pressure was 4 kPa, and the deposition time was 8.0 h.

[0061] 5. The adhesion of the diamond coating on the pretreated cemented carbide substrate of Examples 1-6 and Comparative Example 1 was detected, and the detection results are shown in the following table:

[0062]

[0063]

[0064] From the above table, it can be seen that the adhesion of the diamond coating in Comparative Example 1 is the worst because the cemented carbide substrate is only subjected to the acid-base two-step chemical etching treatment. The adhesion of the diamond coating in Example 1 is enhanced because the cemented carbide substrate is subjected to the acid-base two-step chemical etching treatment + heat treatment. The adhesion of the diamond coating in Examples 2 to 6 is better than that in Example 1 because the cemented carbide substrate is subjected to the acid-base two-step chemical etching treatment + filling with refractory metal powder or refractory metal carbide powder + heat treatment. Except that the adhesion of the diamond coating in Example 5 is equivalent to that in Example 1, the adhesion of the diamond coating in the other examples is better than that in Example 1.

[0065] The SEM image of the indentation for testing the adhesion of the diamond coating on the cemented carbide substrate in Comparative Example 1 is shown in Figure 1 , and the SEM image of the indentation for testing the adhesion of the diamond coating on the cemented carbide substrate in Example 3 is shown in Figure 2 From Figure 1 and Figure 2 , it can be seen that the adhesion of the diamond coating in Example 3 is greatly enhanced compared with that in Comparative Example 1.

[0066] Examples 7-11 and Comparative Example 2

[0067] Examples 7-11 and Comparative Example 2 all use WC-8Co (YG8) cemented carbide as the substrate of the CVD diamond coating.

[0068] 1. The process steps for the composite pretreatment of the cemented carbide substrate in Examples 7-11 are as follows:

[0069] (1) Acid-base two-step chemical etching treatment

[0070] The WC-8Co (YG8) cemented carbide substrate is immersed in anhydrous ethanol for ultrasonic cleaning for 10 min, and then immersed in deionized water for ultrasonic cleaning for 5 min to remove surface impurities.

[0071] The cleaned cemented carbide substrate is immersed in an alkaline solution (Murakami reagent) for ultrasonic bath for 20 min, and the alkaline solution is prepared from KOH, K3[Fe(CN)6] and deionized water, and the mass ratio of KOH: K3[Fe(CN)6]: deionized water is 1:1:10. The cemented carbide substrate after alkaline etching is immersed in an acid solution (Caro acid) for ultrasonic bath for 20 s, and the acid solution is prepared from H2SO4 and H2O2, and the volume ratio of H2SO4: H2O2 is 1:10.

[0072] The etched cemented carbide substrate is immersed in anhydrous ethanol for ultrasonic cleaning for 10 min, and then immersed in deionized water for ultrasonic cleaning for 5 min to remove the acid and alkaline substances.

[0073] (2) filling of refractory metal powder or refractory metal carbide powder

[0074] Example 7 is W powder with FSSS particle size of 0.23 μm, Example 8 is WC powder with FSSS particle size of 0.53 μm, Example 9 is Mo powder with FSSS particle size of 0.32 μm, Example 10 is Cr powder with FSSS particle size of 0.82 μm, and Example 11 is Cr3C2 powder with FSSS particle size of 0.67 μm;

[0075] The cemented carbide substrate of each example after step (1) acid-base chemical etching treatment was immersed in the corresponding suspension of refractory metal powder or refractory metal carbide powder, ultrasonic bath for 10 min, and then placed in an oven at 50°C to dry, thereby obtaining the cemented carbide substrate filled with refractory metal powder or refractory metal carbide powder of each example. The suspension of refractory metal powder or refractory metal carbide powder of each example was prepared as follows: 10 g of refractory metal powder or refractory metal carbide powder, 0.5 g of paraffin and 1.0 g of isomyl were added to 100 mL of hexane, and then stirred uniformly;

[0076] (3) heat treatment

[0077] The cemented carbide substrate filled with refractory metal or metal carbide powder of step (2) was placed in a vacuum furnace, Ar gas was introduced into the furnace to 3 kPa, the temperature was raised to 1230°C at a rate of 1°C-2°C / h, and the temperature was maintained for 2 hours. After the end of the temperature maintaining, the power was turned off, and the furnace was cooled to room temperature. Then the cemented carbide substrate was immersed in anhydrous ethanol for ultrasonic cleaning for 10 min, and then immersed in deionized water for ultrasonic cleaning for 5 min to remove the impurities on the surface. Then the cemented carbide substrate was placed in an oven at 50°C to dry, thereby completing the pretreatment of the cemented carbide substrate.

[0078] 2. Pretreatment of the cemented carbide substrate of Comparative Example 2

[0079] The pretreatment of the cemented carbide substrate of Comparative Example 2 was only acid-base two-step chemical etching treatment, and the operation and process parameters were the same as those of Examples 7-11.

[0080] 3. Diamond coating deposition on the pretreated cemented carbide substrate of Examples 7-11 and Comparative Example 2

[0081] The pretreated cemented carbide substrates of each example and Comparative Example were subjected to diamond coating deposition by hot filament chemical vapor deposition (HF-CVD), and the process parameters were as follows: 9 Ta hot filaments, the distance between each Ta hot filament was 20 mm, the distance between the cemented carbide substrate and the Ta hot filament was 10 mm, the power was 7200 W, CH4 / H2=2.5 / 100 (flow ratio), the total gas pressure was 4 kPa, and the deposition time was 8.0 h.

[0082] 4. The adhesion of the diamond coating on the cemented carbide substrate pretreated in Examples 7-11 and Comparative Example 2 was detected, and the results are shown in the following table:

[0083] Example or Comparative Example Results of the detection of the adhesion of the diamond coating Example 7 HF1 Example 8 HF2 Example 9 HF4 Example 10 HF5 Example 11 HF2 Comparative Example 2 HF6

[0084] As shown in the above table, the adhesion of the diamond coating in Comparative Example 2 is the worst because the cemented carbide substrate is only pretreated by the acid-base two-step chemical etching. The cemented carbide substrate in Examples 7-11 is pretreated by the acid-base two-step chemical etching + filling of refractory metal powder or refractory metal carbide powder + heat treatment, so the adhesion of the diamond coating is better than that in Comparative Example 2, especially in Examples 7, 8 and 11, the adhesion of the diamond coating is greatly enhanced compared with Comparative Example 2.

[0085] Examples 12-15 and Comparative Example 3

[0086] Examples 12-15 and Comparative Example 3 all use WC-12Co (K12UF) cemented carbide as the substrate of the CVD diamond coating.

[0087] 1. The process steps of the composite pretreatment of the cemented carbide substrate in Examples 12-15 are as follows:

[0088] (1) Acid-base two-step chemical etching

[0089] The WC-12Co (K12UF) cemented carbide substrate is immersed in anhydrous ethanol for ultrasonic cleaning for 10 min, and then immersed in deionized water for ultrasonic cleaning for 5 min to remove surface impurities;

[0090] The cleaned cemented carbide substrate is immersed in an alkali solution (Murakami reagent) for ultrasonic bath for 10 min, the alkali solution is prepared from KOH, K3[Fe(CN)6] and deionized water, and the mass ratio of KOH: K3[Fe(CN)6]: deionized water is 1:1:10; the cemented carbide substrate after alkali etching is immersed in an acid solution (Caro acid) for ultrasonic bath for 30 s, the acid solution is prepared from H2SO4 and H2O2, and the volume ratio of H2SO4: H2O2 is 1:10;

[0091] The etched cemented carbide substrate is immersed in anhydrous ethanol for ultrasonic cleaning for 10 min, and then immersed in deionized water for ultrasonic cleaning for 5 min to remove acid and alkali substances;

[0092] (2) Filling of refractory metal powder or refractory metal carbide powder

[0093] Example 12 is a W powder with FSSS particle size of 0.23 μm, Example 13 is a WC powder with FSSS particle size of 0.53 μm, Example 14 is a Mo2C powder with FSSS particle size of 0.83 μm, and Example 15 is a Cr3C2 powder with FSSS particle size of 0.67 μm;

[0094] The cemented carbide substrate of each example subjected to the acid-base chemical etching treatment of step (1) was immersed in a suspension of the corresponding refractory metal powder or refractory metal carbide powder, ultrasonically bathed for 10 minutes, and then placed in an oven to dry at 50°C, thereby obtaining the cemented carbide substrate filled with the refractory metal powder or refractory metal carbide powder of each example. The suspension of the refractory metal powder or refractory metal carbide powder of each example was prepared as follows: 10 g of the refractory metal powder or refractory metal carbide powder, 0.5 g of paraffin wax, and 1.0 g of isopar M were added to 100 mL of hexane, and then stirred uniformly;

[0095] (3) Heat treatment

[0096] The cemented carbide substrate filled with the refractory metal or metal carbide powder of step (2) was placed in a vacuum furnace, H2 gas was introduced into the furnace to a pressure of 2 kPa, the temperature was raised to 1000°C at a rate of 1-2°C / h, and the temperature was maintained for 2 hours. After the temperature maintenance, the power was turned off, and the cemented carbide substrate was cooled to room temperature with the furnace. The cemented carbide substrate was then immersed in anhydrous ethanol and ultrasonically cleaned for 10 minutes, and then immersed in deionized water and ultrasonically cleaned for 5 minutes to remove impurities on the surface. The cemented carbide substrate was then placed in an oven and dried at 50°C, thereby completing the pretreatment of the cemented carbide substrate.

[0097] 2. Pretreatment of the cemented carbide substrate of Comparative Example 3

[0098] The pretreatment of the cemented carbide substrate of Comparative Example 3 was only subjected to the acid-base two-step chemical etching treatment, and the operation and process parameters were the same as those of Examples 12-15.

[0099] 3. Deposition of diamond coating on the pretreated cemented carbide substrate of Examples 12-15 and Comparative Example 2

[0100] The pretreated cemented carbide substrates of each example and Comparative Example were subjected to diamond coating deposition by hot filament chemical vapor deposition (HF-CVD), and the process parameters were as follows: 9 Ta hot filaments, a distance of 20 mm between each Ta hot filament, a distance of 10 mm between the cemented carbide substrate and the Ta hot filaments, a power of 7200 W, CH4 / H2=2.5 / 100 (flow ratio), a total gas pressure of 4 kPa, and a deposition time of 8.0 h.

[0101] 4. The adhesion of the diamond coating on the pretreated cemented carbide substrate of Examples 12-15 and Comparative Example was detected, and the detection results are shown in the following table:

[0102] Example or Comparative Example Results of the detection of the adhesion of the diamond coating Example 12 HF2 Example 13 HF3 Example 14 HF5 Example 15 HF5 Comparative Example 3 Incompleteness of the diamond coating

Claims

1. A method for pretreatment of WC-Co cemented carbide substrate with CVD diamond coating, characterized in that... The process steps are as follows: (1) Two-step acid-base chemical corrosion treatment After cleaning and removing surface impurities from the CVD diamond-coated WC-Co cemented carbide substrate, it is first etched with alkaline solution, then with acid solution, and then cleaned to remove acid and alkaline substances, thus obtaining an acid-alkali etched WC-Co cemented carbide substrate. (2) Heat treatment The WC-Co cemented carbide substrate, after acid and alkali etching treatment, is heated to 1000℃~1300℃ under vacuum, hydrogen protection, or inert gas protection and held for 0.5h~2h. After holding, it is cooled to room temperature with the furnace, and then the surface impurities are removed by cleaning and air drying or baking. This completes the pretreatment of the WC-Co cemented carbide substrate for CVD diamond coating.

2. The pretreatment method for WC-Co cemented carbide substrate composite with CVD diamond coating according to claim 1, characterized in that... In step (1), the alkaline solution is prepared with KOH, K3[Fe(CN)6] and deionized water in a mass ratio of KOH:K3[Fe(CN)6]:deionized water = 1:1:

10. The alkaline corrosion involves immersing the WC-Co cemented carbide substrate in the alkaline solution and ultrasonically bathing it for 10 min to 30 min. The acid solution is prepared with H2SO4 and H2O2 in a volume ratio of H2SO4:H2O2 = 1:

10. The acid corrosion involves immersing the WC-Co cemented carbide substrate in the acid solution and ultrasonically bathing it for 10 s to 30 s.

3. The pretreatment method for WC-Co cemented carbide substrate composite with CVD diamond coating according to claim 1 or 2, characterized in that... In both steps (1) and (2), the WC-Co cemented carbide substrate was first ultrasonically cleaned with anhydrous ethanol and then ultrasonically cleaned with deionized water.

4. A method for pretreatment of WC-Co cemented carbide substrate with CVD diamond coating, characterized in that... The process steps are as follows: (1) Two-step acid-base chemical corrosion treatment After cleaning and removing surface impurities from the CVD diamond-coated WC-Co cemented carbide substrate, it is first etched with alkaline solution, then with acid solution, and then cleaned to remove acid and alkaline substances, thus obtaining an acid-alkali etched WC-Co cemented carbide substrate. (2) Filling with refractory metal powder or refractory metal carbide powder The WC-Co cemented carbide matrix, after acid and alkali etching treatment, is immersed in a suspension of refractory metal powder or refractory metal carbide powder, ultrasonically bathed for 1 min to 10 min, and then dried to obtain a WC-Co cemented carbide matrix filled with refractory metal powder or refractory metal carbide powder. The suspension of refractory metal powder or refractory metal carbide powder is prepared as follows: 10 g of refractory metal powder or refractory metal carbide powder, 0.5 g to 1 g of paraffin wax and 0.5 g to 1 g of surfactant are added to every 100 mL of hexane and stirred evenly. (3) Heat treatment The WC-Co cemented carbide substrate filled with refractory metal powder or refractory metal carbide powder is heated to 1000℃~1300℃ under vacuum, hydrogen protection, or inert gas protection and held for 0.5h~2h. After holding, it is cooled to room temperature with the furnace, and then the surface impurities are removed by cleaning and air drying or baking. This completes the pretreatment of the WC-Co cemented carbide substrate with CVD diamond coating.

5. The pretreatment method for WC-Co cemented carbide substrate composite with CVD diamond coating according to claim 4, characterized in that... In step (2), the refractory metal is at least one of W, Mo, and Cr, and the refractory metal carbide is at least one of WC, Mo2C, and Cr3C2; the surfactant is zinc stearate and / or isocyanate, and when the surfactant is zinc stearate and isocyanate, the mass ratio of zinc stearate to isocyanate is 1:

1.

6. The pretreatment method for WC-Co cemented carbide substrate composite with CVD diamond coating according to claim 4 or 5, characterized in that... In step (2), the refractory metal powder or refractory metal carbide powder has a Fisher particle size ≤ 0.8 μm.

7. The pretreatment method for WC-Co cemented carbide substrate composite with CVD diamond coating according to claim 4 or 5, characterized in that... In step (1), the alkaline solution is prepared with KOH, K3[Fe(CN)6] and deionized water in a mass ratio of KOH:K3[Fe(CN)6]:deionized water = 1:1:

10. The alkaline corrosion involves immersing the WC-Co cemented carbide substrate in the alkaline solution and ultrasonically bathing it for 10 min to 30 min. The acid solution is prepared with H2SO4 and H2O2 in a volume ratio of H2SO4:H2O2 = 1:

10. The acid corrosion involves immersing the WC-Co cemented carbide substrate in the acid solution and ultrasonically bathing it for 10 s to 30 s.

8. The pretreatment method for WC-Co cemented carbide substrate composite with CVD diamond coating according to claim 6, characterized in that... In step (1), the alkaline solution is prepared with KOH, K3[Fe(CN)6] and deionized water in a mass ratio of KOH:K3[Fe(CN)6]:deionized water = 1:1:

10. The alkaline corrosion involves immersing the WC-Co cemented carbide substrate in the alkaline solution and ultrasonically bathing it for 10 min to 30 min. The acid solution is prepared with H2SO4 and H2O2 in a volume ratio of H2SO4:H2O2 = 1:

10. The acid corrosion involves immersing the WC-Co cemented carbide substrate in the acid solution and ultrasonically bathing it for 10 s to 30 s.

9. The pretreatment method for WC-Co cemented carbide substrate composite with CVD diamond coating according to claim 4 or 5, characterized in that... In steps (1) and (3), the WC-Co cemented carbide substrate is cleaned by first ultrasonic cleaning with anhydrous ethanol and then ultrasonic cleaning with deionized water.

10. The pretreatment method for WC-Co cemented carbide substrate composite with CVD diamond coating according to claim 8, characterized in that... In steps (1) and (3), the WC-Co cemented carbide substrate is cleaned by first ultrasonic cleaning with anhydrous ethanol and then ultrasonic cleaning with deionized water.

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