A method for pretreating the surface of a cemented carbide substrate

Abstract

The invention discloses a method for pretreating a cemented carbide substrate surface, and relates to the technical field of cemented carbide. The cemented carbide substrate is first polished and then acid-etched, and then the surface of the cemented carbide substrate is subjected to an infiltration treatment. The infiltration treatment is specifically as follows: ammonium heptamolybdate is coated on the surface of the cemented carbide substrate, and then placed in a carbon dioxide atmosphere, and heating is started to be heated to 1000-1200°C; nitrogen is gradually introduced during the heating process. The present invention first etches the surface of the cemented carbide and then performs an infiltration treatment. The specific infiltration treatment adopted, in a carbon dioxide atmosphere, pre-oxidizes Co and WC, and then further performs nitriding and molybdenizing treatment, thereby avoiding further diffusion of the bonding phase in subsequent processes and further refining the grain size of the cemented carbide substrate surface.

Description

Technical Field

[0001] The invention relates to the field of cemented carbide, in particular to a surface pretreatment method for a cemented carbide substrate. Background Art

[0002] As a tool and structural material, cemented carbide has been widely used in various industries due to its high hardness, high elastic modulus, wear resistance, high temperature resistance, corrosion resistance and other advantages.

[0003] With the development of high-speed cutting technology, people have put forward increasingly stringent requirements for the performance of blades. They require not only good wear resistance, but also impact resistance and sufficient toughness to ensure that the tool does not break during high-speed cutting. For traditional alloys, to ensure the wear resistance of the blade, impact toughness is often sacrificed. Good impact toughness is relatively poor wear resistance. For a long time, people have been looking for a dual-high performance alloy. The emergence of ultrafine nanomaterials has brought people hope. When the grain structure is refined to a certain extent and the grain size in the alloy reaches the nanometer level, the hardness and bending strength of the alloy will be greatly improved, and a dual-high alloy can be obtained.

[0004] The advent of coating technology has, to some extent, solved this problem. High-wear-resistant coatings combined with tough alloy substrates make high-speed cutting possible. However, when chemical vapor deposition of high-wear-resistant coatings is applied to ordinary cemented carbide substrates, an η phase forms between the coating and the substrate, causing cracks and stress concentration. This significantly reduces the alloy's bending strength (by about 20%), leading to chipping and fracture of the blade during early use. Therefore, surface treatment of the substrate is required before coating. Summary of the Invention

[0005] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide a method for pretreating the surface of a cemented carbide substrate.

[0006] The technical solutions of the present invention are as follows:

[0007] A method for pretreating the surface of a cemented carbide substrate comprises the following steps:

[0008] First, the cemented carbide substrate is polished, then acid-etched, and then the surface of the cemented carbide substrate is infiltrated;

[0009] The infiltration treatment is specifically as follows: ammonium heptamolybdate is coated on the surface of the cemented carbide substrate, and then placed in a carbon dioxide atmosphere and heated to 1000-1200° C.; nitrogen is gradually introduced during the heating process.

[0010] As a preferred embodiment of the present invention, the acid solution is a nitric acid solution with a mass concentration of 10-20%.

[0011] As a preferred embodiment of the present invention, after the nitrogen is introduced and mixed with the carbon dioxide, the nitrogen accounts for 20-40%.

[0012] As a preferred embodiment of the present invention, the heating specifically includes a first temperature section of 400-600°C, a second temperature section of 600-800°C for heat preservation, and a third temperature section of 800-1200°C for heat preservation.

[0013] As a preferred embodiment of the present invention, the first temperature section is kept warm for 20-30 minutes, the second temperature section is kept warm for 10-20 minutes, and the third temperature section is kept warm for 5-10 minutes.

[0014] As a preferred solution of the present invention, the polishing adopts a grinding method: specifically, the cemented carbide substrate is subjected to coarse grinding, fine grinding and fine grinding respectively.

[0015] As a preferred embodiment of the present invention, the coarse grinding adopts a diamond grinder with a particle size of 200-600 meshes, the fine grinding adopts a diamond grinder with a particle size of 600-1000 meshes, and the fine grinding adopts a diamond grinder with a particle size of 1000-1500 meshes.

[0016] The beneficial effects of the present invention are:

[0017] The present invention first etches the surface of the cemented carbide and then performs an infiltration treatment. Specifically, the infiltration treatment is to pre-oxidize Co and WC in a carbon dioxide atmosphere, and then further perform nitriding and molybdenizing treatments, thereby avoiding further diffusion of the binder phase in subsequent processes and further refining the grain size on the surface of the cemented carbide substrate. DETAILED DESCRIPTION

[0018] The following embodiments of the present invention are described in detail. The embodiments described below are exemplary and are only used to explain the present invention, and are not to be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this field or the product specifications are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be obtained commercially.

[0019] The technical solution of the present invention is further described below with reference to specific embodiments.

[0020] In the following examples, the cemented carbide substrate adopts WC-20% (Fe / Co / Ni), wherein the mass ratio of Fe:Co:Ni is 10:3:4.

[0021] Example 1

[0022] A method for pretreating the surface of a cemented carbide substrate comprises the following steps:

[0023] First, the cemented carbide substrate is polished, then acid-etched, and then the surface of the cemented carbide substrate is infiltrated;

[0024] The infiltration treatment is specifically as follows: ammonium heptamolybdate is coated on the surface of the cemented carbide substrate, and then placed in a carbon dioxide atmosphere and heated to 1000° C.; nitrogen is gradually introduced during the heating process.

[0025] The acid solution is a nitric acid solution with a mass concentration of 10%.

[0026] After the nitrogen is introduced and mixed with the carbon dioxide, the nitrogen accounts for 20%.

[0027] The heating specifically includes a first temperature section of 400° C., a second temperature section of 60° C. for heat preservation, and a third temperature section of 800-1200° C. for heat preservation.

[0028] The first temperature section is kept warm for 20 minutes, the second temperature section is kept warm for 10 minutes, and the third temperature section is kept warm for 5 minutes.

[0029] The polishing adopts a grinding method: specifically, the cemented carbide substrate is subjected to coarse grinding, fine grinding and fine grinding respectively.

[0030] The coarse grinding adopts a diamond grinder with a particle size of 200 meshes, the fine grinding adopts a diamond grinder with a particle size of 600 meshes, and the fine grinding adopts a diamond grinder with a particle size of 1000 meshes.

[0031] Example 2

[0032] A method for pretreating the surface of a cemented carbide substrate comprises the following steps:

[0033] First, the cemented carbide substrate is polished, then acid-etched, and then the surface of the cemented carbide substrate is infiltrated;

[0034] The infiltration treatment is specifically as follows: ammonium heptamolybdate is coated on the surface of the cemented carbide substrate, and then placed in a carbon dioxide atmosphere and heated to 1100° C.; nitrogen is gradually introduced during the heating process.

[0035] The acid solution is a nitric acid solution with a mass concentration of 15%.

[0036] After the nitrogen is introduced and mixed with the carbon dioxide, the nitrogen accounts for 20%.

[0037] The heating specifically includes a first temperature section of 500° C., a second temperature section of 700° C. for heat preservation, and a third temperature section of 1000° C. for heat preservation.

[0038] The first temperature section is kept warm for 25 minutes, the second temperature section is kept warm for 15 minutes, and the third temperature section is kept warm for 7 minutes.

[0039] The polishing adopts a grinding method: specifically, the cemented carbide substrate is subjected to coarse grinding, fine grinding and fine grinding respectively.

[0040] The coarse grinding adopts a diamond grinder with a particle size of 300 meshes, the fine grinding adopts a diamond grinder with a particle size of 800 meshes, and the fine grinding adopts a diamond grinder with a particle size of 1200 meshes.

[0041] Example 3

[0042] A method for pretreating the surface of a cemented carbide substrate comprises the following steps:

[0043] First, the cemented carbide substrate is polished, then acid-etched, and then the surface of the cemented carbide substrate is infiltrated;

[0044] The infiltration treatment is specifically as follows: ammonium heptamolybdate is coated on the surface of the cemented carbide substrate, and then placed in a carbon dioxide atmosphere and heated to 1200° C.; nitrogen is gradually introduced during the heating process.

[0045] The acid solution is a nitric acid solution with a mass concentration of 20%.

[0046] After the nitrogen is introduced and mixed with the carbon dioxide, the nitrogen accounts for 20%.

[0047] The heating specifically includes a first temperature section of 600° C., a second temperature section of 800° C. for heat preservation, and a third temperature section of 1200° C. for heat preservation.

[0048] The first temperature section is kept warm for 30 minutes, the second temperature section is kept warm for 20 minutes, and the third temperature section is kept warm for 10 minutes.

[0049] The polishing adopts a grinding method: specifically, the cemented carbide substrate is subjected to coarse grinding, fine grinding and fine grinding respectively.

[0050] The coarse grinding adopts a diamond grinder with a particle size of 600 meshes, the fine grinding adopts a diamond grinder with a particle size of 1000 meshes, and the fine grinding adopts a diamond grinder with a particle size of 1500 meshes.

[0051] Example 4

[0052] A method for pretreating the surface of a cemented carbide substrate comprises the following steps:

[0053] First, the cemented carbide substrate is polished, then acid-etched, and then the surface of the cemented carbide substrate is infiltrated;

[0054] The infiltration treatment is specifically as follows: ammonium heptamolybdate is coated on the surface of the cemented carbide substrate, and then placed in a carbon dioxide atmosphere and heated to 1000° C.; nitrogen is gradually introduced during the heating process.

[0055] The acid solution is a nitric acid solution with a mass concentration of 12%.

[0056] After the nitrogen is introduced and mixed with the carbon dioxide, the nitrogen accounts for 30%.

[0057] The heating specifically includes a first temperature section of 500° C., a second temperature section of 700° C. for heat preservation, and a third temperature section of 1200° C. for heat preservation.

[0058] The first temperature section is kept warm for 30 minutes, the second temperature section is kept warm for 15 minutes, and the third temperature section is kept warm for 7 minutes.

[0059] The polishing adopts a grinding method: specifically, the cemented carbide substrate is subjected to coarse grinding, fine grinding and fine grinding respectively.

[0060] The coarse grinding adopts a diamond grinder with a particle size of 400 meshes, the fine grinding adopts a diamond grinder with a particle size of 800 meshes, and the fine grinding adopts a diamond grinder with a particle size of 1200 meshes.

[0061] Example 5

[0062] A method for pretreating the surface of a cemented carbide substrate comprises the following steps:

[0063] First, the cemented carbide substrate is polished, then acid-etched, and then the surface of the cemented carbide substrate is infiltrated;

[0064] The infiltration treatment is specifically as follows: ammonium heptamolybdate is coated on the surface of the cemented carbide substrate, and then placed in a carbon dioxide atmosphere and heated to 1200° C.; nitrogen is gradually introduced during the heating process.

[0065] The acid solution is a nitric acid solution with a mass concentration of 15%.

[0066] After the nitrogen is introduced and mixed with the carbon dioxide, the nitrogen accounts for 40%.

[0067] The heating specifically includes a first temperature section of 600° C., a second temperature section of 800° C. for heat preservation, and a third temperature section of 1200° C. for heat preservation.

[0068] The first temperature section is kept warm for 28 minutes, the second temperature section is kept warm for 18 minutes, and the third temperature section is kept warm for 7 minutes.

[0069] The polishing adopts a grinding method: specifically, the cemented carbide substrate is subjected to coarse grinding, fine grinding and fine grinding respectively.

[0070] The coarse grinding adopts a diamond grinder with a particle size of 600 meshes, the fine grinding adopts a diamond grinder with a particle size of 800 meshes, and the fine grinding adopts a diamond grinder with a particle size of 1200 meshes.

[0071] Comparative Example 1 (no infiltration treatment)

[0072] A method for pretreating the surface of a cemented carbide substrate comprises the following steps:

[0073] The cemented carbide substrate is first polished and then acid-etched;

[0074] The acid solution is a nitric acid solution with a mass concentration of 15%.

[0075] The polishing adopts a grinding method: specifically, the cemented carbide substrate is subjected to coarse grinding, fine grinding and fine grinding respectively.

[0076] The coarse grinding adopts a diamond grinder with a particle size of 600 meshes, the fine grinding adopts a diamond grinder with a particle size of 800 meshes, and the fine grinding adopts a diamond grinder with a particle size of 1200 meshes.

[0077] The performance of the above examples and comparative examples were tested, and the test results are shown in Table 1.

[0078] Sample Matrix surface grain size (μm) Surface hardness (HV) Example 1 3 379 Example 2 5 369 Example 3 4 375 Example 4 4 372 Example 5 3 378 Comparative Example 1 12 172

[0079] As can be seen from the above table, the performance of the embodiment is better than that of the comparative example. The main reason may be that the embodiment first etches the cemented carbide surface and then performs infiltration treatment. Specifically, the infiltration treatment adopted is to pre-oxidize Co and WC in a carbon dioxide atmosphere, and then further perform nitriding and molybdenizing treatment, which avoids further diffusion of the binder phase in the subsequent process and further refines the grain size on the surface of the cemented carbide substrate.

[0080] The above-described embodiments merely represent preferred implementations of the present invention. While the descriptions thereof are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make various other corresponding changes and modifications based on the technical solutions and concepts described above, and all such changes and modifications should fall within the scope of protection of the claims of the present invention.

Claims

1. A method for pretreating the surface of a cemented carbide substrate, characterized in that: The following steps are involved: First, the cemented carbide substrate is polished, then acid-etched, and then the surface of the cemented carbide substrate is infiltrated; The infiltration treatment is specifically as follows: ammonium heptamolybdate is coated on the surface of the cemented carbide substrate, and then placed in a carbon dioxide atmosphere and heated to 1000-1200° C.; nitrogen is gradually introduced during the heating process; After nitrogen and carbon dioxide are mixed, nitrogen accounts for 20-40%; The heating specifically includes a first temperature section of 400-600°C, a second temperature section of 600-800°C for heat preservation, and a third temperature section of 800-1200°C for heat preservation; The first temperature section is kept warm for 20-30 minutes, the second temperature section is kept warm for 10-20 minutes, and the third temperature section is kept warm for 5-10 minutes; The cemented carbide substrate adopts WC-20%Fe / Co / Ni, wherein the mass ratio of Fe:Co:Ni is 10:3:

4.

2. A method for pretreating the surface of a cemented carbide substrate according to claim 1, characterized in that: The acid solution is a nitric acid solution with a mass concentration of 10-20%.

3. The method for pretreating the surface of a cemented carbide substrate according to claim 1, wherein: The polishing adopts a grinding method: specifically, the cemented carbide substrate is subjected to coarse grinding, fine grinding and fine grinding respectively.

4. A method for pretreating the surface of a cemented carbide substrate according to claim 3, characterized in that: The coarse grinding adopts a diamond grinder with a particle size of 200-600 meshes, the fine grinding adopts a diamond grinder with a particle size of 600-1000 meshes, and the fine grinding adopts a diamond grinder with a particle size of 1000-1500 meshes.