A β - removed cemented carbide and its preparation method

Abstract

The present invention discloses a β - layer - removed cemented carbide and a preparation method thereof, which relates to the technical field of cemented carbides, and comprises the following steps: mixing the following raw materials of nitrogen - free cemented carbide in parts by weight, 80 - 85 parts of WC, 3 - 7 parts of (Ti, W)C, 5 - 8 parts of Co, 1 - 3 parts of TaC, 1 - 3 parts of NbC; S2: through wet grinding, spray drying, and pressing into shape to obtain a green compact; subjecting the green compact to positive - pressure removal of the forming agent with H2, heating it in vacuum to 150 - 350 °C, then performing atmosphere sintering at 1270 - 1350 °C with a nitrogen - containing reaction gas, and finally heating it in vacuum to 1420 - 1490 °C for sintering for 0.5 - 1.5 h. When the sintering is completed and cooled to 1000 - 1100 °C, a mixed gas of CH4 and H2 is introduced. By using nitrogen - free reaction raw materials, nitriding treatment is carried out by introducing a nitrogen - containing reaction gas in a micro - pressure atmosphere, and at the same time, a trace amount of carbon - containing gas is added. Combining with the process of temperature reduction, a certain amount of carbon element is further provided to adjust the gradient of the β - layer - removed layer, forming an effective toughness region on the surface of the alloy and improving the performance of the alloy.

Description

Technical Field

[0001] The present invention relates to the technical field of cemented carbides, and particularly relates to a β-phase layer-removed cemented carbide and a preparation method thereof. Background Art

[0002] During continuous cutting of carbon steel and alloy steel, the friction between the cutting and the rake face of the tool is large, and the average temperature in the cutting area is high. Therefore, cemented carbide tools are required to have high hot hardness, wear resistance, anti-bonding property and oxidation resistance.

[0003] In order to improve the service life and cutting performance of cemented carbide cutting tools, chemical vapor deposition and physical vapor deposition methods are usually used to coat a thin layer of high-hardness wear-resistant materials such as TiN, TiC, Ti(C, N) or Al2O3 on the surface of the alloy. However, due to the different thermal expansion coefficients of different materials, the coated tool materials are prone to crack due to the influence of thermal stress during the cooling process.

[0004] In order to prevent material failure caused by the initiation and propagation of cracks as much as possible to obtain high-performance cemented carbide cutting tool materials, usually before coating, the alloy substrate is subjected to gradient sintering. After gradient sintering, a ductile region lacking cubic carbides and carbonitrides is formed in the surface region of the coated substrate, and the content of the corresponding binder is higher than that of the coated substrate. Therefore, research on this process technology is required. 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 β-phase layer-removed cemented carbide and a preparation method thereof.

[0006] The technical solution of the present invention is as follows:

[0007] A preparation method of a β-phase layer-removed cemented carbide, comprising the following steps:

[0008] S1: Mix the nitrogen-free cemented carbide raw materials in the following weight parts: 80-85 parts of WC, 3-7 parts of (Ti, W)C, 5-8 parts of Co, 1-3 parts of TaC, 1-3 parts of NbC;

[0009] S2: Obtain a green compact by wet grinding, spray drying and pressing into shape;

[0010] S3: Remove the molding agent from the green compact under positive pressure of H2, heat it in vacuum to 150-350 °C, then perform atmosphere sintering at 1270-1350 °C with a nitrogen-containing reaction gas, and finally heat it in vacuum to 1420-1490 °C and sinter for 0.5-1.5 h. When the sintering is completed and cooled to 1000-1100 °C, a mixed gas of CH4 and H2 is introduced.

[0011] As a preferred embodiment of the present invention, in step S3, the pressure of the nitrogen-containing reaction gas is controlled at 50 - 150 mbar.

[0012] As a preferred embodiment of the present invention, in step S3, the nitrogen-containing reaction gas is nitrogen.

[0013] As a preferred embodiment of the present invention, in step S3, the nitrogen-containing reaction gas contains 0.5 - 3 vt% methane.

[0014] As a preferred embodiment of the present invention, in step S3, the volume ratio of CH4 to H2 in the mixed gas is 1 - 3:1.

[0015] As a preferred embodiment of the present invention, in step S3, the time for introducing the mixed gas at 1000 - 1100 °C is 20 - 40 min.

[0016] The beneficial effects of the present invention are as follows: By using nitrogen-free reaction raw materials and introducing nitrogen-containing reaction gas for nitriding treatment in a micro-pressure atmosphere, while adding a small amount of carbon-containing gas, and further providing a certain amount of carbon element during the cooling process to adjust the gradient of the decarburized layer, an effective ductile region is formed on the alloy surface, preventing the diffusion of internal cracks in the alloy and improving the performance of the alloy. Detailed Embodiments

[0017] The embodiments of the present invention are described in detail below. The described embodiments are exemplary and are only used to explain the present invention, and should not be construed as a limitation to the present invention. For those not specified in the embodiments regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in this field or according to the product specifications. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0018] The technical solutions of the present invention are further described below with specific embodiments.

[0019] Example 1

[0020] A method for preparing a decarburized layer cemented carbide includes the following steps:

[0021] S1: Mix the following weight parts of nitrogen-free cemented carbide raw materials: 80 parts of WC, 3 parts of (Ti, W)C, 5 parts of Co, 2 parts of TaC, and 2 parts of NbC;

[0022] S2: Through wet grinding, spray drying, and pressing into shape, a green compact is obtained;

[0023] S3: Subject the green compact to H2 positive pressure to remove the forming agent, heat it in vacuum to 150 °C, then conduct atmosphere sintering at 1270 °C with a nitrogen-containing reaction gas, and finally heat it in vacuum to 1420 °C for sintering for 1 h. When cooling to 1100 °C after sintering, introduce a mixed gas of CH4 and H2.

[0024] In step S3, the pressure of the nitrogen-containing reaction gas is controlled at 50 mbar.

[0025] In step S3, the nitrogen-containing reaction gas is nitrogen.

[0026] In step S3, the nitrogen-containing reaction gas contains 0.5 vt% methane by volume.

[0027] In step S3, the volume ratio of CH4 to H2 in the mixed gas is 1:1.

[0028] In step S3, the time for introducing the mixed gas is 20 min.

[0029] Example 2

[0030] A method for preparing β-layer removed cemented carbide includes the following steps:

[0031] S1: Mix the following weight parts of nitrogen-free cemented carbide raw materials: 80 parts of WC, 3 parts of (Ti, W)C, 5 parts of Co, 2 parts of TaC, and 2 parts of NbC;

[0032] S2: Obtain a green compact through wet grinding, spray drying, and pressing.

[0033] S3: Subject the green compact to H2 positive pressure to remove the forming agent, heat it in vacuum to 150 °C, then conduct atmosphere sintering at 1270 °C with a nitrogen-containing reaction gas, and finally heat it in vacuum to 1420 °C for sintering for 1 h. When cooling to 1100 °C after sintering, introduce a mixed gas of CH4 and H2.

[0034] In step S3, the pressure of the nitrogen-containing reaction gas is controlled at 100 mbar.

[0035] In step S3, the nitrogen-containing reaction gas is nitrogen.

[0036] In step S3, the nitrogen-containing reaction gas contains 0.5 vt% methane by volume.

[0037] In step S3, the volume ratio of CH4 to H2 in the mixed gas is 1:1.

[0038] In step S3, the time for introducing the mixed gas is 20 min.

[0039] Example 3

[0040] A preparation method of β-phase removed cemented carbide, comprising the following steps:

[0041] S1: Mix the following parts by weight of nitrogen-free cemented carbide raw materials: 80 parts of WC, 3 parts of (Ti, W)C, 5 parts of Co, 2 parts of TaC, and 2 parts of NbC;

[0042] S2: Obtain a green compact by wet grinding, spray drying, and pressing into shape;

[0043] S3: Remove the molding agent from the green compact under positive pressure of H2, heat it in vacuum to 150 °C, then perform atmosphere sintering at 1270 °C with a nitrogen-containing reaction gas, and finally heat it in vacuum to 1420 °C for sintering for 1 h. When it is cooled to 1100 °C after sintering, introduce a mixed gas of CH4 and H2.

[0044] In step S3, the pressure of the nitrogen-containing reaction gas is controlled at 150 mbar.

[0045] In step S3, the nitrogen-containing reaction gas is nitrogen.

[0046] In step S3, the nitrogen-containing reaction gas contains 0.5 vt% of methane.

[0047] In step S3, the volume ratio of CH4 to H2 in the mixed gas is 1:1.

[0048] In step S3, the time for introducing the mixed gas is 20 min.

[0049] Example 4

[0050] A preparation method of β-phase removed cemented carbide, comprising the following steps:

[0051] S1: Mix the following parts by weight of nitrogen-free cemented carbide raw materials: 80 parts of WC, 3 parts of (Ti, W)C, 5 parts of Co, 2 parts of TaC, and 2 parts of NbC;

[0052] S2: Obtain a green compact by wet grinding, spray drying, and pressing into shape;

[0053] S3: Remove the molding agent from the green compact under positive pressure of H2, heat it in vacuum to 150 °C, then perform atmosphere sintering at 1270 °C with a nitrogen-containing reaction gas, and finally heat it in vacuum to 1420 °C for sintering for 1 h. When it is cooled to 1100 °C after sintering, introduce a mixed gas of CH4 and H2.

[0054] In step S3, the pressure of the nitrogen-containing reaction gas is controlled at 100 mbar.

[0055] In step S3, the nitrogen-containing reaction gas is nitrogen.

[0056] In step S3, the nitrogen-containing reaction gas contains 1 vt% methane.

[0057] In step S3, the volume ratio of CH4 to H2 in the mixed gas is 1:1.

[0058] In step S3, the time for introducing the mixed gas is 20 min.

[0059] Example 5

[0060] A method for preparing a β-layer removed cemented carbide includes the following steps:

[0061] S1: Mix the following weight parts of nitrogen-free cemented carbide raw materials: 80 parts of WC, 3 parts of (Ti, W)C, 5 parts of Co, 2 parts of TaC, and 2 parts of NbC;

[0062] S2: Obtain a green compact through wet grinding, spray drying, and pressing into shape;

[0063] S3: Remove the forming agent from the green compact under positive pressure with H2, heat it in vacuum to 150 °C, then perform atmosphere sintering at 1270 °C with a nitrogen-containing reaction gas, and finally heat it in vacuum to 1420 °C for sintering for 1 h. When cooling to 1100 °C after sintering, introduce a mixed gas of CH4 and H2.

[0064] In step S3, the pressure of the nitrogen-containing reaction gas is controlled at 100 mbar.

[0065] In step S3, the nitrogen-containing reaction gas is nitrogen.

[0066] In step S3, the nitrogen-containing reaction gas contains 1.5 vt% methane.

[0067] In step S3, the volume ratio of CH4 to H2 in the mixed gas is 1:1.

[0068] In step S3, the time for introducing the mixed gas is 20 min.

[0069] Example 6

[0070] Changes made based on Example 4, specifically, the nitrogen-containing reaction gas contains 2 vt% methane.

[0071] Example 7

[0072] Changes made based on Example 4, specifically, the nitrogen-containing reaction gas contains 3 vt% methane.

[0073] Example 8

[0074] Changes made on the basis of Example 4, specifically, the volume ratio of CH4 to H2 in the mixed gas is 2:1.

[0075] Example 9

[0076] Changes made on the basis of Example 4, specifically, the volume ratio of CH4 to H2 in the mixed gas is 3:1.

[0077] Comparative Example 1 (nitrogen-containing reaction gas without carbon-containing gas)

[0078] A method for preparing a β-layer removed cemented carbide, comprising the following steps:

[0079] S1: Mix the following parts by weight of nitrogen-free cemented carbide raw materials, 80 parts of WC, 3 parts of (Ti, W)C, 5 parts of Co, 2 parts of TaC, 2 parts of NbC;

[0080] S2: Through wet grinding, spray drying, and pressing into shape, a green compact is obtained;

[0081] S3: The green compact is subjected to positive pressure of H2 to remove the forming agent, vacuum-heated to 150 °C, then sintered in an atmosphere of nitrogen-containing reaction gas at 1270 °C, and finally vacuum-heated to 1420 °C and sintered for 1 h. When cooled to 1100 °C after sintering, a mixed gas of CH4 and H2 is introduced.

[0082] In step S3, the pressure of the nitrogen-containing reaction gas is controlled at 100 mbar.

[0083] In step S3, the nitrogen-containing reaction gas is nitrogen.

[0084] In step S3, the volume ratio of CH4 to H2 in the mixed gas is 1:1.

[0085] In step S3, the time for introducing the mixed gas is 20 min.

[0086] Comparative Example 2 (no mixed gas is introduced during the cooling stage)

[0087] A method for preparing a β-layer removed cemented carbide, comprising the following steps:

[0088] S1: Mix the following parts by weight of nitrogen-free cemented carbide raw materials, 80 parts of WC, 3 parts of (Ti, W)C, 5 parts of Co, 2 parts of TaC, 2 parts of NbC;

[0089] S2: Through wet grinding, spray drying, and pressing into shape, a green compact is obtained;

[0090] S3: The green compact is subjected to positive pressure with H2 to remove the molding agent, heated in vacuum to 150 °C, then sintered in an atmosphere with a nitrogen-containing reaction gas at 1270 °C, and finally sintered at 1420 °C for 1 h in vacuum and cooled in the furnace.

[0091] In step S3, the pressure of the nitrogen-containing reaction gas is controlled at 100 mbar.

[0092] In step S3, the nitrogen-containing reaction gas is nitrogen.

[0093] In step S3, the nitrogen-containing reaction gas contains 1 vt% methane by volume.

[0094] In step S3, the volume ratio of CH4 to H2 in the mixed gas is 1:1.

[0095] In step S3, the time for introducing the mixed gas is 20 min.

[0096] The above examples and comparative examples were subjected to performance tests, and the test results are shown in Table 1.

[0097] Table 1 Performance test results of examples and comparative examples

[0098]

[0099]

[0100] As can be seen from the above table, the performance of the examples is better than that of the comparative examples. The possible reasons are as follows: By using nitrogen-free reaction raw materials, nitriding treatment is carried out by introducing a nitrogen-containing reaction gas under a slightly positive pressure atmosphere, and a carbon-containing gas is added in a trace amount. Combining with the process of cooling, a certain amount of carbon element is further provided to adjust the gradient of the β-depleted layer, forming an effective ductile region on the surface of the alloy, preventing the diffusion of internal cracks in the alloy, and improving the performance of the alloy.

[0101] The above-described examples only represent the preferred embodiments of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, according to the technical solutions and concepts described above, various other corresponding changes and deformations can also be made, and all of these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a β-layered cemented carbide, characterized in that: The following steps are involved: S1: Mix the following nitrogen-free cemented carbide raw materials in parts by weight: 80-85 parts of WC, 3-7 parts of (Ti, W)C, 5-8 parts of Co, 1-3 parts of TaC, and 1-3 parts of NbC; S2: through wet grinding, spray drying, pressing and forming, a green compact is obtained; S3: The green compact is removed from the molding agent by H2 positive pressure, vacuum heated to 150-350 ° C, then sintered at 1270-1350 ° C in a nitrogen-containing reaction gas atmosphere, and finally vacuum heated to 1420-1490 ° C for 0.5-1.5h. After sintering, it is cooled to 1000-1100 ° C and a mixed gas of CH4 and H2 is introduced; In step S3, the nitrogen-containing reaction gas contains 0.5-3vt% of methane; In step S3, the volume ratio of CH4 and H2 in the mixed gas is 1-3:1; In step S3, the time for introducing the mixed gas at 1000-1100° C. is 20-40 minutes.

2. The method for preparing a β-layer-free cemented carbide according to claim 1, characterized in that: In step S3, the pressure of the nitrogen-containing reaction gas is controlled at 50-150 mbar.

3. The method for preparing a β-layer-free cemented carbide according to claim 1, characterized in that: In step S3 , the nitrogen-containing reaction gas is nitrogen.

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