A method for filling WC-based ceramic self-lubricating layers under extreme pressure

Abstract

This invention discloses a method for filling a WC-based ceramic self-lubricating layer under extreme pressure, belonging to the field of inorganic non-metallic material preparation technology. The method includes: first, uniformly mixing CBN or diamond powder with WC powder, pre-pressing the mixture, and encapsulating it with a metal inclusion; then, sintering the encapsulated sample under high temperature and high pressure, removing the metal inclusion to prepare a WC-based porous ceramic; next, encapsulating the shaped WC-based porous ceramic with a layer of self-lubricating powder, and then encapsulating it with another metal inclusion; subsequently, subjecting the encapsulated sample to high temperature and high pressure or high pressure treatment, removing the metal inclusion and residual self-lubricating bulk material, obtaining a WC-based self-lubricating ceramic containing a lubricating layer. The WC-based self-lubricating ceramic prepared by this invention has the same mechanical properties as the non-lubricating ceramic; its wear resistance is significantly improved compared to the non-lubricating layer.

Description

Technical Field

[0001] This invention relates to the field of inorganic non-metallic material preparation technology, and more specifically to a method for filling WC-based ceramic self-lubricating layers under extreme pressure. Background Technology

[0002] High-speed cutting is a crucial method for driving the rapid upgrading of the manufacturing industry. However, as cutting speeds increase, the area covered by cutting fluid decreases, and the resulting extreme thermal loads place stringent demands on the performance of tool materials. WC-based self-lubricating ceramic tools can autonomously form a lubricating film during cutting, effectively improving cutting conditions. However, due to the relatively "soft" nature of the ceramic lubricating components, mechanical properties are significantly reduced. Controlling the content, particle size, and distribution of the ceramic lubricating components is the main way to narrow the gap in mechanical properties between self-lubricating ceramics and traditional ceramics. However, when the matrix and lubricating particles are sintered together, the lubricating particles, acting as "impurities," hinder interatomic bonding in the matrix and form pores, inevitably leading to a decrease in mechanical properties. How to eliminate the influence of lubricating components on the mechanical properties of ceramics and achieve synergistic enhancement of mechanical and lubrication properties is an urgent problem to be solved.

[0003] Studies have shown that preparing self-lubricating ceramic materials with excellent wear resistance requires meeting conditions such as high hardness, high toughness, high density, and good high-temperature stability, which presents a significant engineering challenge.

[0004] Therefore, how to develop a WC-based ceramic self-lubricating layer filling method driven by extreme pressure is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a method for filling WC-based ceramic self-lubricating layers under extreme pressure.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for filling a WC-based ceramic self-lubricating layer under extreme pressure includes the following steps:

[0008] (1) Mix CBN or diamond powder with WC polycrystalline powder in a volume ratio of (1-3):(7-9) to obtain mixed powder. Pre-press the mixed powder into shape and wrap it with a metal encapsulation.

[0009] (2) The mixed powder in the metal inclusion body is sintered under high temperature and high pressure. The specific steps are: first, pressurize to the set pressure, then heat up, keep warm, then slowly cool down to room temperature, and finally keep pressure for a period of time and then slowly reduce pressure.

[0010] (3) Take out the sample after sintering in step (2), remove the metal inclusions outside the sample to obtain WC-based porous ceramic, and then process it into the specified shape;

[0011] (4) WC-based porous ceramics are coated with a layer of self-lubricating powder and then wrapped with a metal encapsulation.

[0012] The self-lubricating powder is a metal powder. The metal inclusion is treated with high temperature and high pressure. The specific steps are: first, pressurize to the set pressure, then heat to the melting point of the metal powder under the set pressure, keep warm, stop heating, continue to keep pressure for a period of time, and then slowly reduce the pressure.

[0013] Alternatively, the self-lubricating powder is a non-metallic powder, and the metal encapsulation is subjected to high pressure treatment. The specific steps are: first, pressurize to the set pressure, maintain the pressure for a period of time, and then slowly reduce the pressure.

[0014] (5) Take out the sample after step (4), remove the metal inclusions and residual self-lubricating blocks outside the sample, and obtain WC-based self-lubricating ceramic containing a lubricating layer.

[0015] Furthermore, in step (1), the grain size of CBN or diamond powder is 0.2 to 50 μm, and the grain size of WC powder is 0.2 to 10 μm.

[0016] Furthermore, in steps (2) and (4), the pressure is set to 5.5 GPa.

[0017] Furthermore, in step (1), the self-lubricating powder is MoS2, WS2, Cu or Al powder, and the particle size of the self-lubricating powder is 10nm-10μm.

[0018] Furthermore, in step (1), the pre-compression pressure is 0.1 GPa and the holding time is 1 s.

[0019] Furthermore, in step (2), the pressure increase rate and pressure decrease rate are 5 GPa / min, the temperature is increased to 300-1800℃, the heating rate is 100℃ / min, the holding time is 2-50 min, the cooling rate is 10℃ / min, the pressure is held for 5 min and then slowly reduced to 0 GPa.

[0020] Furthermore, the metal inclusions in steps (2) and (4) are Mo, Zr, or Ta.

[0021] Furthermore, in step (4), the thickness of the self-lubricating powder layer is 0.5 mm or more.

[0022] Further, in step (4), the self-lubricating powder is a metal powder, which is subjected to high temperature and high pressure treatment. The pressure increase rate and pressure decrease rate are 5GPa / min. The temperature is increased to the melting point of the metal powder at 5.5GPa, the heating rate is 100℃ / min, the holding time is 5min, the heating is stopped, the pressure is held for another 5min, and then the pressure is slowly reduced to 0GPa.

[0023] Alternatively, the self-lubricating powder is a non-metallic powder, subjected to high pressure treatment, with a pressurization rate and a depressurization rate of 5 GPa / min, a holding time of 5 min, and then slowly depressurized to 0 GPa.

[0024] The beneficial effects of this invention are as follows: This invention adds a hard, difficult-to-sinter material as a second phase to the WC matrix, which improves the mechanical properties of WC ceramics and forms interconnected pores between WC ceramic grains to prepare porous ceramics; by using extreme temperature and pressure loads, solid / liquid self-lubricating particles are filled into the micropores of the ceramic along the ceramic pores, and the particle size of the self-lubricating particles can be much larger than the pore size of the ceramic micropores.

[0025] This invention separates the ceramic sintering and lubricant phase filling processes. First, a ceramic matrix with natural pores is synthesized. Then, extreme pressure is used to "squeeze" lubricant particles into the ceramic pores. This not only completely solves the problem of decreased mechanical properties caused by lubricant particles, but also further enhances the mechanical properties of the ceramic, achieving synergistic enhancement of mechanical and lubrication properties.

[0026] Adding CBN particles / diamond as a second phase to the WC matrix improves the hardness and toughness of WC ceramics and creates interconnected micropores between WC ceramic grains to prepare microporous ceramics.

[0027] Lubricating particles are wrapped around sintered WC-based microporous ceramics, and extreme temperature and pressure loads are used to squeeze the lubricating particles into the interior of the ceramics to form a lubricating layer, giving WC-based ceramics self-lubricating properties.

[0028] The WC-based self-lubricating ceramics prepared by the method of this invention have the same mechanical properties as non-lubricating ceramics;

[0029] The wear resistance of WC-based self-lubricating ceramics prepared by the method of this invention is significantly improved compared with that of non-lubricating layers. Attached Figure Description

[0030] Figure 1 This is a process flow diagram of the present invention;

[0031] Figure 2 This is a scanning electron microscope (SEM) image of the WC-CBN-MoS2 self-lubricating ceramic from Example 1.

[0032] Figure 3 Scanning electron microscopy (SEM) image of WC-CBN-Cu self-lubricating ceramic in Example 2.

[0033] Figure 4 This is a scanning electron microscope (SEM) image of the self-lubricating ceramic WC-CBN-WS2 in Example 3;

[0034] Figure 5 The image shows a scanning electron microscope (SEM) analysis of the self-lubricating ceramic of Comparative Example 1, WC-CBN-MoS2. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] A method for filling WC-based ceramic self-lubricating layers under extreme pressure includes the following steps:

[0038] (1) CBN powder with a grain size of 5-10 μm and WC powder with a grain size of 200 nm are mixed evenly at a volume ratio of 1:4 to obtain a mixed powder. The mixed powder is then pre-pressed. The pre-pressing pressure is 0.1 GPa and the holding time is 1 s. The molded sample is then wrapped with Mo metal inclusions.

[0039] (2) The molded sample with metal inclusions is loaded into the high-pressure sintering unit and then sintered at high temperature and high pressure. The specific steps are as follows: first, the pressure is increased to the set pressure of 5.5 GPa and the pressure increase rate is 5 GPa / min, then the temperature is increased to 1350℃ and the temperature increase rate is 100℃ / min. The temperature is held for 10 min, and then the temperature is reduced to room temperature at a cooling rate of 10℃ / min. The pressure is held for 5 min and then the pressure is slowly reduced to 0 GPa at a cooling rate of 5 GPa / min.

[0040] (3) Take out the sample after high temperature and high pressure sintering in step (2), remove the metal Mo inclusions wrapped around the sample to obtain WC-CBN-based porous ceramics, and then process them into a cylindrical shape with a height of 3mm and a diameter of 10mm.

[0041] (4) WC-CBN-based porous ceramics are coated with a layer of self-lubricating powder MoS2 powder with a particle size of 1 μm and a layer thickness of 1 mm. Then, they are coated with a metal inclusion body made of Mo. The sample with the metal inclusion body is loaded into a high-pressure unit and then subjected to high-pressure treatment. The specific steps are as follows: first, the pressure is increased to the set pressure of 5.5 GPa at a rate of 5 GPa / min, and the pressure is held for 5 min before slowly decreasing the pressure to 0 GPa at a rate of 5 GPa / min.

[0042] (5) Take out the sample after high pressure treatment in step (4), remove the metal inclusions and residual self-lubricating blocks that wrap around the sample, and obtain WC-CBN-MoS2 ceramic containing a lubricating layer.

[0043] The ceramic lubricating layer thickness was 1.5 μm; the Vickers hardness of the WC-CBN microporous ceramic was measured to be 33.5 ± 1.1 GPa, and the fracture toughness was 9.95 ± 0.5 MPa. 1 / 2 The nanoindentation hardness of the WC-CBN-MoS2 ceramic lubricating layer was measured to be 34.5 ± 1.2 GPa, and the fracture toughness was 10.05 ± 0.6 MPa. 1 / 2 The hardness and toughness of WC-based ceramics remain unchanged before and after the lubricating layer is filled.

[0044] The wear resistance of WC-CBN microporous ceramics and WC-CBN-MoS2 ceramics was measured by rubbing them against a cemented carbide ball (YG6) (pressure 10N, friction time 15min, rotation speed 400rpm). The wear rate of WC-CBN microporous ceramics was 150×10⁻⁶. -6 mm 3 / Nm, the wear rate of WC-CBN-MoS2 is 20×10 -6 mm 3 / Nm, the wear resistance of WC-based ceramics after high-pressure filling of the lubricating layer is significantly improved compared with that before filling.

[0045] Example 2

[0046] A method for filling WC-based ceramic self-lubricating layers under extreme pressure includes the following steps:

[0047] (1) Diamond powder with a grain size of 5-10 μm and WC powder with a grain size of 200 nm are mixed evenly at a volume ratio of 1:4 to obtain a mixed powder; the mixed powder is pre-pressed into shape under a pressure of 0.1 GPa and the pressure holding time is 1 s; the shaped sample is then wrapped with Zr metal inclusions.

[0048] (2) The molded sample with metal inclusions is loaded into the high-pressure sintering unit and then sintered at high temperature and high pressure. The specific steps are as follows: First, the pressure is increased to the set pressure of 5.5 GPa and the pressure increase rate is 5 GPa / min. Then, the temperature is increased to 1400℃ and the temperature increase rate is 100℃ / min. The temperature is held for 30 min and then cooled to room temperature at a rate of 10℃ / min. The pressure is then held for 5 min and then slowly reduced to 0 GPa at a rate of 5 GPa / min.

[0049] (3) Take out the sample after high temperature and high pressure sintering in step (2), remove the Zr metal inclusions wrapped around the sample to obtain WC-diamond microporous ceramic, and then process it into a cylindrical shape with a height of 3mm and a diameter of 10mm.

[0050] (4) WC-based porous ceramics are coated with a layer of self-lubricating Cu powder with a particle size of 10 μm and a layer thickness of 2 mm. Then, they are coated with a metal inclusion body, which is Zr. The raw material with the metal inclusion body is loaded into a high-pressure sintering unit and then subjected to high temperature and high pressure treatment. The specific steps are as follows: First, the pressure is increased to the set pressure of 5.5 GPa at a rate of 5 GPa / min. Then, the temperature is increased to the melting point of Cu at 5.5 GPa, which is 1400℃ at a rate of 100℃ / min. The temperature is held for 5 min. Then, the heating is stopped and the pressure is held for another 5 min before slowly reducing the pressure to 0 GPa at a rate of 5 GPa / min.

[0051] (5) Take out the sample after the high temperature and high pressure treatment in step (4), remove the metal inclusions and residual self-lubricating blocks that wrap the sample, and obtain WC-diamond-Cu ceramic containing a lubricating layer.

[0052] The ceramic lubricating layer thickness was 10 μm; the Vickers hardness of the WC-diamond microporous ceramic was measured to be 28.3 ± 1.3 GPa, and the fracture toughness was 8.45 ± 0.5 MPa. 1 / 2 The nanoindentation hardness of the WC-diamond-Cu ceramic lubricating layer was measured to be 27.5 ± 1.1 GPa, and the fracture toughness was 8.05 ± 0.4 MPa. 1 / 2 The hardness and toughness of WC-based ceramics remain unchanged before and after the lubricating layer is filled.

[0053] The wear resistance of WC-diamond microporous ceramics and WC-diamond-Cu was measured by rubbing them against cemented carbide balls (YG6) (pressure 10N, friction time 15min, rotation speed 400rpm). The wear rate of WC-diamond microporous ceramics was 180×10⁻⁶. -6 mm 3 / Nm, the wear rate of WC-diamond-Cu is 80×10 -6 mm 3 / Nm, the wear resistance of WC-based ceramics after high-pressure filling of the lubricating layer is significantly improved compared with that before filling.

[0054] Example 3

[0055] A method for filling WC-based ceramic self-lubricating layers under extreme pressure includes the following steps:

[0056] (1) CBN powder with a grain size of 5-10 μm and WC powder with a grain size of 200 nm are mixed evenly at a volume ratio of 1:4 to obtain a mixed powder. The mixed powder is then pre-pressed. The pre-pressing pressure is 0.1 GPa and the holding time is 1 s. The molded sample is then wrapped with Mo metal inclusions.

[0057] (2) The molded sample with metal inclusions is loaded into the high-pressure sintering unit and then sintered at high temperature and high pressure. The specific steps are as follows: first, the pressure is increased to the set pressure of 5.5 GPa and the pressure increase rate is 5 GPa / min, then the temperature is increased to 1450℃ and the temperature increase rate is 100℃ / min. The temperature is held for 10 min, and then the temperature is reduced to room temperature at a cooling rate of 10℃ / min. The pressure is held for 5 min and then the pressure is slowly reduced to 0 GPa at a cooling rate of 5 GPa / min.

[0058] (3) Take out the sample after high temperature and high pressure sintering in step (2), remove the metal Ta inclusions wrapped around the sample to obtain WC-CBN-based porous ceramics, and then process them into a cylindrical shape with a height of 3mm and a diameter of 10mm.

[0059] (4) WC-based porous ceramics are coated with a layer of self-lubricating powder WS2 powder. The particle size of the self-lubricating powder is 1 μm and the layer thickness is 1 mm. Then, it is coated with a metal inclusion body. The metal inclusion body material is Mo. The sample with the metal inclusion body is loaded into the high-pressure unit and then subjected to high-pressure treatment. The specific steps are as follows: first, the pressure is increased to the set pressure of 5.5 GPa at a rate of 5 GPa / min, and the pressure is held for 5 min. Then, the pressure is slowly reduced to 0 GPa at a rate of 5 GPa / min.

[0060] (5) Take out the sample after high pressure treatment in step (4), remove the metal inclusions and residual self-lubricating blocks that wrap around the sample, and obtain WC-CBN-WS2 ceramic containing a lubricating layer.

[0061] The ceramic lubricating layer thickness was 60 μm; the Vickers hardness of the WC-CBN microporous ceramic was measured to be 32.5 ± 1.1 GPa, and the fracture toughness was 9.85 ± 0.5 MPa. 1 / 2 The nanoindentation hardness of the WC-CBN-WS2 ceramic lubricating layer was measured to be 34.5 ± 1.2 GPa, and the fracture toughness was 10.05 ± 0.6 MPa. 1 / 2 The hardness and toughness of WC-based ceramics remain unchanged before and after the lubricating layer is filled.

[0062] The wear resistance of WC-CBN microporous ceramics and WC-CBN-WS2 ceramics was measured by rubbing them against a cemented carbide ball (YG6) (pressure 10N, friction time 15min, rotation speed 400rpm). The wear rate of WC-CBN microporous ceramics was 148×10⁻⁶. -6 mm 3 / Nm, the wear rate of WC-CBN-WS2 is 19×10 -6 mm 3 / Nm, the wear resistance of WC-based ceramics after high-pressure filling of the lubricating layer is significantly improved compared with that before filling.

[0063] Comparative Example 1

[0064] The preparation method of WC-CBN-MoS2 self-lubricating ceramics includes the following steps:

[0065] (1) CBN powder with a grain size of 5-10 μm, WC powder with a grain size of 200 nm, and MoS2 powder with a grain size of 1 μm were mixed evenly at a volume ratio of 75:20:5 to obtain a mixed powder, which was then pre-pressed. The pre-pressing pressure was 0.1 GPa, and the holding time was 1 s. The resulting molded sample was then encapsulated with a metal inclusion body, which was Mo.

[0066] (2) The molded sample with metal inclusions is loaded into the high-pressure sintering unit and then sintered at high temperature and high pressure. The specific steps are as follows: first, the pressure is increased to the set pressure of 5.5 GPa and the pressure increase rate is 5 GPa / min. Then, the temperature is increased to 1350℃ and held for 30 min. The temperature is then reduced to room temperature at a rate of 10℃ / min. The pressure is then maintained for 5 min and then slowly reduced to 0 GPa at a rate of 5 GPa / min.

[0067] (3) Take out the sample after high temperature and high pressure sintering in step (2), remove the metal inclusions wrapped around the sample, and obtain WC-CBN-MoS2 self-lubricating ceramic.

[0068] The Vickers hardness of the WC-CBN-MoS2 self-lubricating ceramic in Comparative Example 1 was measured to be 27.5 ± 1.0 GPa, and its fracture toughness was 7.95 ± 0.5 MPa. 1 / 2 The wear resistance of WC-CBN-MoS2 was measured by rubbing it against a cemented carbide ball (YG6) (pressure 10N, friction time 15min, rotation speed 400rpm). The wear rate of WC-CBN-MoS2 was 80×10⁻⁶. -6 mm 3 / Nm. The hardness, toughness, and wear resistance of the WC-CBN-MoS2 self-lubricating ceramic prepared in Comparative Example 1 are all lower than those of the WC-based self-lubricating ceramics prepared in Examples 1-3.

[0069] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for filling a WC-based ceramic self-lubricating layer under extreme pressure, characterized in that, Includes the following steps: (1) Mix CBN or diamond powder with WC polycrystalline powder in a volume ratio of (1-3):(7-9) to obtain mixed powder. Pre-press the mixed powder into shape and wrap it with a metal encapsulation. (2) The mixed powder in the metal inclusion body is sintered under high temperature and high pressure. The specific steps are: first, pressurize to the set pressure, then heat up, keep warm, then slowly cool down to room temperature, and finally continue to keep pressure for a period of time before slowly reducing pressure. (3) Take out the sample after sintering in step (2), remove the metal inclusions on the sample to obtain WC-based porous ceramic, and then process it into the specified shape; (4) Coat the outside of the processed WC-based porous ceramic with a layer of self-lubricating powder, and then wrap it with a metal encapsulation body; The self-lubricating powder is a metal powder. The metal inclusion is treated with high temperature and high pressure. The specific steps are: first, pressurize to the set pressure, then heat to the melting point of the metal powder under the set pressure, keep warm, stop heating, continue to keep pressure for a period of time, and then slowly reduce the pressure. Alternatively, the self-lubricating powder is a non-metallic powder, and the metal encapsulation is subjected to high pressure treatment. The specific steps are: first, pressurize to the set pressure, maintain the pressure for a period of time, and then slowly reduce the pressure. (5) Take out the sample after step (4), remove the metal inclusions and residual self-lubricating blocks outside the sample, and obtain WC-based self-lubricating ceramic containing a lubricating layer; In steps (2) and (4), the pressure is set to 5.5 GPa; In step (2), the temperature is raised to 1300-1800℃ and held for 2-50 minutes.

2. The method for filling a WC-based ceramic self-lubricating layer under extreme pressure as described in claim 1, characterized in that, In step (1), the grain size of CBN or diamond powder is 0.2 to 50 μm, and the grain size of WC powder is 0.2 to 10 μm.

3. The method for filling a WC-based ceramic self-lubricating layer under extreme pressure as described in claim 1, characterized in that, In step (1), the self-lubricating powder is MoS2, WS2, Cu or Al powder, and the particle size of the self-lubricating powder is 10 nm-10 μm.

4. The method for filling a WC-based ceramic self-lubricating layer under extreme pressure as described in claim 1, characterized in that, In step (1), the pre-compression pressure is 0.1 GPa and the holding time is 1s.

5. The method for filling a WC-based ceramic self-lubricating layer under extreme pressure as described in claim 1, characterized in that, In step (2), the pressure increase rate and pressure decrease rate are 5 GPa / min, the heating rate is 100℃ / min, the cooling rate is 10℃ / min, and the pressure holding time is 5 min before slowly reducing the pressure to 0 GPa.

6. The method for filling a WC-based ceramic self-lubricating layer under extreme pressure as described in claim 1, characterized in that, The metal inclusions in steps (1) and (4) are Mo, Zr or Ta.

7. The method for filling a WC-based ceramic self-lubricating layer under extreme pressure as described in claim 1, characterized in that, In step (4), the thickness of the self-lubricating powder layer is 0.5 mm or more.

8. The method for filling a WC-based ceramic self-lubricating layer under extreme pressure as described in claim 1, characterized in that, In step (4), the self-lubricating powder is a metal powder, which is sintered under high temperature and high pressure. The pressure increase rate and pressure decrease rate are 5 GPa / min. The temperature is increased to the melting point of the metal powder at 5.5 GPa, the heating rate is 100℃ / min, the holding time is 5 min, the heating is stopped, the pressure is held for another 5 min, and then the pressure is slowly reduced to 0 GPa. Alternatively, the self-lubricating powder is a non-metallic powder, subjected to high pressure treatment, with a pressurization rate and a depressurization rate of 5 GPa / min, a holding time of 5 min, and then slowly depressurized to 0 GPa.

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