CN110527891A - Hard alloy in low cobalt surface diamond coating and preparation method thereof - Google Patents

Abstract

The invention relates to a diamond coating on the surface of a low-cobalt hard alloy and a preparation method thereof. The hard alloy with a low cobalt content is used as a base material to deposit a diamond film. Using the excellent physical properties of graphene to improve the toughness of low-cobalt cemented carbide, it is used as a base material for diamond coating. Reduce the chemical pretreatment time before diamond coating, avoid the corrosion damage to the base material caused by the long-term chemical reaction, and better maintain the dimensional accuracy of the product. At the same time, the thermal diffusion effect of cobalt in the diamond coating deposition process is alleviated, and the adhesion strength between the coating and the substrate is improved. The dual effects of improving the toughness of the diamond-coated cemented carbide substrate and eliminating the adverse effects of cobalt elements are realized, which provides an effective method for improving the performance of diamond-coated cemented carbide products.

Description

Diamond coating on low-cobalt hard alloy surface and preparation method thereof

technical field

The invention belongs to the field of diamond coating and its preparation, in particular to a low-cobalt hard alloy surface diamond coating and a preparation method thereof.

Background technique

The high hardness, high wear resistance, high thermal conductivity, low friction coefficient and good chemical inertness of diamond coating make it widely used in the field of tools and molds. Depositing a diamond coating on the surface of a cemented carbide tool can not only greatly increase the service life of the tool, but also improve the surface quality of the workpiece.

In order to balance the hardness and toughness of the base material, the cobalt content of the cemented carbide base selected for the diamond coating is usually 6wt.%-8wt.%. However, in order to eliminate the graphitization effect of the cobalt element in the substrate material during the deposition of the diamond coating, the cemented carbide substrate must be pretreated by "chemical corrosion to remove cobalt" before the diamond coating is prepared. The higher the cobalt content of the substrate, the longer the chemical etching time. At the same time of "cobalt removal", it will inevitably damage the tungsten carbide structure in the matrix, thus affecting the performance of the matrix material. The performance of the diamond-coated product cannot achieve the desired effect.

According to the patent search of the existing technology, Chinese patent application Nos. 201510673007.4 and 03117958.4 proposed to use gradient cemented carbide with a cobalt-poor surface layer as the substrate material to prepare a diamond coating to solve the effect of cobalt on the deposition of the diamond coating. At the same time, the strength and toughness of the matrix are taken into account. However, during the deposition of the diamond coating on the cobalt-rich layer at the core of the gradient cemented carbide substrate, due to the heating of the substrate, the thermal diffusion of cobalt will still cause the graphitization of the diamond coating and reduce the adhesion strength of the film substrate.

Contents of the invention

The technical problem to be solved by the present invention is to provide a cemented carbide substrate toughened diamond coating and its preparation method, which overcomes the cobalt content of 6wt.%～8wt.% in the hard alloy used in the diamond coating in the prior art. %, in order to obtain a better pretreatment effect, it is necessary to carry out chemical pretreatment for a long time, while "removing cobalt", it also damages the structural properties of the matrix. In addition, the high cobalt content inside the substrate has a strong thermal diffusion effect during the deposition of the diamond coating, resulting in the technical problem of low bonding strength between the diamond coating and the substrate. In the present invention, the cemented carbide substrate with low cobalt content is toughened and deposited with a diamond coating.

A kind of diamond coating of the present invention, described coating is deposited diamond thin film with cemented carbide as matrix material;

It is characterized in that, by mass percentage, the raw material components of cemented carbide include: graphene (powder) 0.1wt.% ~ 1wt.%, cobalt 2wt.% ~ 3wt.%, tungsten carbide (powder) 97.9wt.% - 96wt.%.

A kind of preparation method of diamond coating of the present invention comprises:

(1) Mixing dispersed graphene, cobalt powder and tungsten carbide powder by ball milling to obtain a slurry, vacuum drying, and sintering the matrix to obtain a cemented carbide matrix material;

(2) pretreating the above-mentioned substrate, and depositing a diamond coating, to obtain.

The preferred mode of above-mentioned preparation method is as follows:

The graphene dispersed in the step (1) is specifically: using dehydrated alcohol as the dispersion solution, the proportion of dehydrated alcohol and graphene is 100mL:(0.1～0.5)g, utilizing the ultrasonic oscillation dispersion process, wherein the ultrasonic frequency It is 40KHz; the duty ratio of ultrasonic working time is 1:1; the time of ultrasonic oscillation is 4~6h.

The specific process parameters of ball milling in the step (1) are: the balls used are cemented carbide WC-3wt.% Co balls with a diameter of 5mm, the speed of the ball mill is 300-500rpm, and the ball milling time is 6-8h; The ratio of water ethanol: powder: grinding ball is: (1～2)mL:1g:(7～10)g.

The vacuum drying in the step (1) is as follows: the mixed and stirred slurry is placed in a vacuum drying oven for drying. During the drying process, the heating temperature is 90-100° C. until there is no visible liquid in the slurry, Stop heating (turn off the heating function), and dry naturally for 2-3 hours. During the whole drying process, keep the pressure in the vacuum chamber at 10000-15000Pa.

Sintering molding in the step (1): After the dried powder is pressed into the shape required by the design, vacuum pressure sintering method is used to sinter molding at a temperature of 1380° C. and a pressure of 40 MPa.

The pretreatment in the step (2) is specifically: immersing the substrate in an alkali solution for 10 minutes, cleaning, and drying, then immersing the alkali-treated substrate in an acid solution to react naturally for 10 seconds, cleaning, and drying; using diamond powder and The mixed solution of glycerol is ground, washed, and dried; the lye is potassium ferricyanide: potassium hydroxide: water = 1g: 1g: 10mL; the acid solution is hydrochloric acid: hydrogen peroxide = 1mL: 4mL.

The deposition in the step (2) is specifically: using the hot wire chemical vapor deposition method, placing the pretreated substrate in the chemical vapor deposition equipment, and after the vacuum chamber pressure of the equipment reaches below 5Pa, input the reaction working gas methane The flow rate is 10-20 sccm, the hydrogen flow rate is 1000-2000 sccm, the reaction pressure is adjusted to 2000-4000 Pa, and the coating deposition time is 6-10 hours. The invention provides a diamond coating prepared by the method.

The invention provides an application of the diamond coating.

Beneficial effect

(1) The present invention solves the problem that the high cobalt content in the cemented carbide substrate of the diamond coating has an adverse effect on the coating and the inability to coordinate the strength and toughness of the substrate in the prior art, and provides a low cobalt content hard alloy used for the diamond coating. Toughening process of alloy matrix and preparation method of coating;

(2) Utilize the excellent characteristics of graphene such as high strength and good toughness to improve the toughness of the low-cobalt content cemented carbide substrate. The composition of graphene is carbon, and no other impurity elements are introduced during the preparation of cemented carbide, so that The composition of the will not be affected;

(3) When cemented carbide with low cobalt content is used for diamond coating, the chemical corrosion time of "alkali + acid" in the pretreatment stage is reduced, avoiding the adverse effects of long-term chemical corrosion on the properties of cemented carbide materials and the finished workpiece The impact of dimensional accuracy, and also avoid the thermal diffusion of high cobalt content in traditional cemented carbide during the deposition process, resulting in poor coating quality and poor bonding strength of the film base;

(4) The present invention utilizes the excellent physical properties of graphene to improve the toughness of cemented carbide with low cobalt content, which is used as the base material of diamond coating, reduces the chemical pretreatment time before diamond coating, and avoids long-term chemical reaction Corrosion damage to the base material, better maintain the dimensional accuracy of the product. At the same time, it alleviates the thermal diffusion of cobalt in the diamond coating deposition process, improves the adhesion strength between the coating and the substrate, and realizes the dual effects of improving the toughness of the diamond-coated cemented carbide substrate and eliminating the adverse effects of cobalt. Diamond-coated cemented carbide product performance provides an effective method.

Description of drawings

Fig. 1 is the indentation morphology of the diamond coating on the surface of a common cemented carbide (6wt.% Co) substrate made in comparative examples;

Fig. 2 is the indentation morphology of the diamond coating on the surface of the graphene reinforced low cobalt content (3wt.% Co) cemented carbide (0.3wt.% graphene) substrate obtained in Example 1.

Fig. 3 is the indentation morphology of the diamond coating on the surface of the graphene reinforced low cobalt content (3wt.% Co) cemented carbide (0.5wt.% graphene) substrate obtained in Example 2.

Detailed ways

Below in conjunction with specific embodiment, further illustrate the present invention. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

The graphene involved in the examples and comparative examples is a commercially available product with a sheet diameter of 5-10 microns and a thickness of 3-10 nanometers; cobalt powder is a commercially available product with a particle diameter of 1 micron; tungsten carbide powder is a commercially available product with a particle diameter of 0.8 microns in diameter.

Example 1

Graphene-Enhanced Diamond Coating Deposition on Low Cobalt Content (3wt.% Co) Cemented Carbide (0.3wt.% Graphene) Substrates.

(1) Graphene dispersion: Weigh 0.3g of graphene powder with a precision electronic balance, pour it into 100mL of absolute ethanol, use a cell smasher, set the ultrasonic frequency to 40KHz; the duty ratio of the ultrasonic working time is 1:1 ; The time of ultrasonic oscillation is 4h.

(2) Ball mill mixing: Weigh 2.991g of cobalt powder and 96.709g of tungsten carbide powder with a precision electronic balance, and pour the graphene-alcohol solution in (1) into a ball mill jar. Weigh 700 g of cemented carbide (WC-wt.3% Co) balls with a diameter of 5 mm and put them into a ball mill jar. Add 100 mL of absolute ethanol into the ball mill tank, set the ball mill speed to 400 rpm, and ball mill for 8 hours.

(3) Vacuum drying: the ball-milled slurry is placed in a vacuum drying oven for drying. Set the pressure in the drying box to 15000Pa, and the heating temperature to 90°C. When there is no visible liquid in the slurry, turn off the heating function and let it dry naturally for 3 hours.

(4) Matrix sintering and molding: the dried powder is sieved with a 120-mesh sieve, and preformed by pressing with a powder tablet press. A vacuum sintering furnace is used, the sintering temperature is set at 1380°C, the pressure is 40MPa, and the sintering time is 40min. After sintering the sample, use a metallographic grinding and polishing machine to grind and polish the surface of the substrate into a mirror surface.

(5) Substrate pretreatment: After the substrate in step (4) is ultrasonically cleaned with absolute ethanol, it is blown dry. Submerge the substrate in alkaline solution (potassium ferricyanide:potassium hydroxide:water=1g:1g:10mL) for 10min, wash and dry. Then immerse the alkali-treated substrate in an acid solution (hydrochloric acid: hydrogen peroxide = 1 mL: 4 mL) to react naturally for 10 seconds, wash and dry. Grind with a mixed solution of diamond powder and glycerin, wash and dry.

(6) Diamond coating deposition: using the hot wire chemical vapor deposition method, the substrate pretreated in step (5) is placed in the chemical vapor deposition equipment, and after the vacuum chamber pressure of the equipment reaches below 5Pa, input the reaction work The gas methane flow rate is 15 sccm, the hydrogen gas flow rate is 1000 sccm, the reaction pressure is adjusted to 3000 Pa, and the coating deposition time is 6 hours.

Example 2

Graphene-Enhanced Diamond Coating Deposition on Low Cobalt Content (3wt.% Co) Cemented Carbide (0.5wt.% Graphene) Substrates.

(1) Graphene dispersion: Weigh 0.5g of graphene powder with a precision electronic balance, pour it into 100mL of absolute ethanol, use a cell pulverizer, set the ultrasonic frequency to 40KHz; the duty ratio of the ultrasonic working time is: 1: 1; The time of ultrasonic oscillation is 4h.

(2) Ball mill mixing: Weigh 2.985g of cobalt powder and 96.515g of tungsten carbide powder with a precision electronic balance, and pour the graphene-alcohol solution in (1) into a ball mill jar. Weigh 1000 g of cemented carbide (WC-wt.3% Co) balls with a diameter of 5 mm and put them into a ball mill jar. Add 100 mL of absolute ethanol into the ball mill tank, set the ball mill speed to 400 rpm, and ball mill for 8 hours.

(3) Vacuum drying: the ball-milled slurry is placed in a vacuum drying oven for drying. Set the pressure in the drying box to 15000Pa, and the heating temperature to 90°C. When there is no visible liquid in the slurry, turn off the heating function and let it dry naturally for 3 hours.

(4) Matrix sintering and molding: the dried powder is sieved with a 120-mesh sieve, and preformed by pressing with a powder tablet press. A vacuum sintering furnace is used, the sintering temperature is set at 1380°C, the pressure is 40MPa, and the sintering time is 40min. After sintering the sample, use a metallographic grinding and polishing machine to grind and polish the surface of the substrate into a mirror surface.

(5) Substrate pretreatment: After the substrate in step (4) is ultrasonically cleaned with absolute ethanol, it is blown dry. Submerge the substrate in alkaline solution (potassium ferricyanide:potassium hydroxide:water=1g:1g:10mL) for 10min, wash and dry. Then immerse the alkali-treated substrate in an acid solution (hydrochloric acid: hydrogen peroxide = 1 mL: 4 mL) to react naturally for 10 seconds, wash and dry. Grind with a mixed solution of diamond powder and glycerin, wash and dry.

(6) Diamond coating deposition: using the hot wire chemical vapor deposition method, the substrate pretreated in step (5) is placed in the chemical vapor deposition equipment, and after the vacuum chamber pressure of the equipment reaches below 5Pa, input the reaction work The gas methane flow rate is 15 sccm, the hydrogen gas flow rate is 1000 sccm, the reaction pressure is adjusted to 3000 Pa, and the coating deposition time is 6 hours.

comparative example

Ordinary cemented carbide (6wt.% Co) substrate diamond coating deposition.

(1) Ball mill mixing: Weigh 6g of cobalt powder and 94g of tungsten carbide powder with a precision electronic balance and pour them into a ball mill jar. Weigh 1000 g of cemented carbide (WC-wt.6% Co) balls with a diameter of 5 mm and put them into a ball mill jar. Add 200 mL of absolute ethanol into the ball mill tank, set the ball mill speed to 400 rpm, and ball mill for 8 hours.

(2) Vacuum drying: the ball-milled slurry is placed in a vacuum drying oven for drying. Set the pressure in the drying box to 15000Pa, and the heating temperature to 90°C. When there is no visible liquid in the slurry, turn off the heating function and let it dry naturally for 3 hours.

(3) Matrix sintering and forming: the dried powder is sieved through a 120-mesh screen, and then pressed into a preform by a powder tablet press. A vacuum sintering furnace is used, the sintering temperature is set at 1380°C, the pressure is 40MPa, and the sintering time is 40min. After sintering the sample, use a metallographic grinding and polishing machine to grind and polish the surface of the substrate into a mirror surface. Compared

(4) Substrate pretreatment: After the substrate in step (3) is ultrasonically cleaned with absolute ethanol, it is blown dry. Submerge the substrate in alkaline solution (potassium ferricyanide:potassium hydroxide:water=1g:1g:10mL) for 10min, wash and dry. Then immerse the alkali-treated substrate in an acid solution (hydrochloric acid: hydrogen peroxide = 1 mL: 4 mL) to react naturally for 10 seconds, wash and dry. Grind with a mixed solution of diamond powder and glycerin, wash and dry.

(5) Diamond coating deposition: using the hot wire chemical vapor deposition method, place the pretreated substrate in step (4) in the chemical vapor deposition equipment, and input the reaction work after the vacuum chamber pressure of the equipment reaches below 5Pa. The gas methane flow rate is 15 sccm, the hydrogen gas flow rate is 1000 sccm, the reaction pressure is adjusted to 3000 Pa, and the coating deposition time is 6 hours.

Utilize microhardness tester to detect respectively the sample made by step (4) in embodiment 1, the sample made by step (4) in embodiment 2, the sample made by step (3) in the comparative example , calculated by indentation load and indentation crack growth length, the fracture toughness values in the three cases are 13.1±0.1MPa·m ^1/2 , 12.9±0.1MPa·m ^1/2 and 10.9±0.1MPa·m ^{1 /2} . The result shows that the process method of the present invention can improve the toughness of cemented carbide.

According to GB/T 230.1-2018 "Rockwell Hardness Test of Metallic Materials Part 1: Test Method", the indentation test is carried out with a diamond conical indenter (cone angle 120°, top curvature radius 0.2mm) and a test force of 980N. The indentation morphology was examined with a scanning electron microscope. The diamond-coated samples of ordinary cemented carbide substrates and the diamond-coated samples prepared in Example 1 and Example 2 were detected by the above method, and the indentation morphology is shown in Figure 1, Figure 2 and Figure 3, respectively. It can be seen that the coating peeling area of the sample surface in Fig. 1 is larger than that of the sample surfaces in Fig. 2 and Fig. 3 . The results show that the coating adhesion strength of the low-cobalt-content graphene reinforced cemented carbide substrate surface prepared by the method of the present invention is higher than that of ordinary cemented carbide with higher cobalt content.

Claims (10)

1. a kind of diamond coatings, the coating is using hard alloy as basis material depositing diamond film；

It is characterized in that, by mass percentage, the raw material components of hard alloy include: graphene 0.1~1%, cobalt 2~3%, carbon Change tungsten 97.9-96%.

2. a kind of preparation method of diamond coatings, comprising:

(1) by the graphene of dispersion, cobalt powder and tungsten carbide ball milling mixing, slurry is obtained, is dried in vacuo, sinter molding obtains To hard alloy substrate；

(2) by above-mentioned substrate pretreated, deposition of diamond coatings to get.

3. preparation method according to claim 2, which is characterized in that the graphene dispersed in the step (1) specifically: adopt It is to disperse solution with dehydrated alcohol, the proportion of dehydrated alcohol and graphene is 100mL:(0.1~0.5) g, utilize sonic oscillation point Day labor skill, wherein supersonic frequency is 40KHz；The duty ratio of ultrasound works time is 1:1；The time of sonic oscillation is 4~6h.

4. preparation method according to claim 2, which is characterized in that ball milling mixing specific process parameter in the step (1) Are as follows: for the abrading-ball used for the hard alloy WC-3wt.%Co ball of diameter 5mm, the revolving speed of ball mill is 300~500rpm, ball milling Time is 6~8h.

5. preparation method according to claim 2, which is characterized in that vacuum drying in the step (1) are as follows: drying process In, heating temperature is 90~100 DEG C, until in slurry without visible liquid when, stop heating, spontaneously dry 2~3h, dry overall process In, the holding indoor pressure of vacuum is 10000~15000Pa.

6. preparation method according to claim 2, which is characterized in that the temperature of sinter molding is 1380 in the step (1) DEG C, pressure 40MPa.

7. preparation method according to claim 2, which is characterized in that pretreatment in the step (2) specifically: soak matrix It not in alkaline solution treatment 10min, cleans, drying, then the matrix after alkali process is immersed in acid solution natural reaction 10s, clean, Drying；It is ground, is cleaned with the mixed solution of bortz powder and glycerine, drying；Wherein lye is the potassium ferricyanide: potassium hydroxide: Water=1g:1g:10mL；Acid solution is hydrochloric acid: hydrogen peroxide=1mL:4mL.

8. preparation method according to claim 2, which is characterized in that deposition in the step (2) specifically: use heated filament It learns vapor deposition method pretreated matrix is placed in chemical vapor depsotition equipment, the vacuum chamber pressure to equipment reaches After 5Pa or less, input reaction 10~20sccm of working gas methane flow, 1000~2000sccm of hydrogen flowing quantity adjust reaction Pressure is 2000~4000Pa, and coat deposition time is 6~10h.

9. a kind of diamond coatings of claim 2 the method preparation.

10. a kind of application of diamond coatings described in claim 1.