Microcrystalline Wear-Resistant Alumina Ceramics and Its Preparation Method

Abstract

The present invention belongs to the technical field of alumina ceramic preparation, and specifically relates to a microcrystalline wear-resistant alumina ceramic and a preparation method thereof. The microcrystalline wear-resistant alumina ceramic is composed of the following raw materials: fused corundum powder, gibbsite, diopside, calcium fluorosilicate, neodymium oxide, nickel aluminate, strontium oxide, and sodium tripolyphosphate. The microcrystalline wear-resistant alumina ceramic of the present invention uses fused corundum powder and gibbsite as the main raw materials to fundamentally ensure the mechanical properties of the prepared alumina ceramic; uses diopside and calcium fluorosilicate as fluxes to reduce the firing temperature of the alumina ceramic and improve the density; uses neodymium oxide, nickel aluminate, and strontium oxide as wear-resistant additives, and through the synergistic effect among the three, by improving the microstructure of the alumina ceramic, avoiding stress concentration at grain boundaries and generating a second reinforcing phase to improve the wear resistance of the alumina ceramic. Thus, it is ensured that the prepared alumina ceramic has excellent wear resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of alumina ceramic preparation, and particularly relates to a microcrystalline wear-resistant alumina ceramic and a preparation method thereof. Background Art

[0002] Microcrystalline alumina ceramic refers to an alumina ceramic material mainly made of high-purity α-Al 2 O 3 powder, which is made by various ceramic processes and has a crystal grain size of less than 6 μm and corundum as the main crystal phase. It has excellent properties such as high melting point, high hardness, good mechanical properties, corrosion resistance, and insulation. Corundum is an extremely hard material in nature, with a Mohs hardness of 9, second only to diamond. The strength of corundum ceramic is very high, with a melting point of 2050 °C, and this high strength can still be maintained at temperatures above 1000 °C. It can also be used under high-temperature and oxygen-rich conditions for a long time, far superior to ordinary steel and alloy steel. The thermal conductivity of corundum is very good, with a thermal conductivity of 29 W / m·K at room temperature, only slightly lower than that of steel and iron, and the dielectric loss at high frequencies is lower than 10 -4 , and it is one of the best high-frequency insulating materials.

[0003] Microcrystalline alumina ceramics can usually be divided into two types: high-purity type and ordinary type. High-purity microcrystalline alumina ceramic refers to an alumina ceramic material with an Al 2 O 3 content of more than 99.9%. Its sintering temperature is as high as 1650 - 1990 °C, and the transmission wavelength is in the range of 1 - 6 μm. Utilizing its light transmittance and alkali metal corrosion resistance, it is commonly used as the lamp tube of high-pressure sodium lamps.

[0004] Ordinary microcrystalline alumina ceramics can be divided into varieties such as 99, 95, 92, 90, 85 porcelain according to different Al 2 O 3 contents (sometimes those with an Al 2 O 3 content of 80% or 75% are also classified into the ordinary alumina ceramic series). Among them, 99 alumina ceramic materials are often used to make high-temperature crucibles, refractory furnace tubes, and other special wear-resistant materials (such as ceramic bearings, ceramic seals, and water valve plates), and can be used as integrated circuit substrates and high-frequency insulating materials in the electronics industry, and are commonly used as catalyst carriers in the chemical industry, etc.; 95, 92, and 90 alumina ceramics are mainly used as corrosion-resistant, wear-resistant materials, and wear-resistant components; in 85 porcelain, due to the addition of some talc, the electrical properties and mechanical strength are improved, and it can be sealed with metals such as niobium and tantalum and used as devices for electro-vacuum devices, etc.

[0005] However, the chemical bond of alumina ceramic materials is an ionic bond, which has strong directionality and high binding energy, resulting in high brittleness, strong crack sensitivity, and poor wear resistance. The wear resistance of alumina ceramic materials greatly limits the popularization and application of this material. Therefore, how to effectively improve the wear resistance of alumina ceramics is the core issue in the research field of alumina ceramic materials. Summary of the Invention

[0006] The purpose of the present invention is to provide a microcrystalline wear-resistant alumina ceramic. The microcrystalline alumina ceramic has excellent wear resistance; the present invention also provides a preparation method thereof at the same time.

[0007] The microcrystalline wear-resistant alumina ceramic described in the present invention is composed of the following raw materials in parts by weight: 80-83 parts of fused corundum powder, 17-20 parts of gibbsite, 0.4-0.6 parts of diopside, 1.3-1.5 parts of calcium fluorosilicate, 0.1-0.13 parts of neodymium oxide, 1.2-1.4 parts of nickel aluminate, 0.1-0.15 parts of strontium oxide, and 5-6 parts of sodium tripolyphosphate.

[0008] Among them:

[0009] The particle size of the fused corundum powder is 14-20 μm.

[0010] The microcrystalline wear-resistant alumina ceramic described in the present invention takes fused corundum powder and gibbsite as the main components. Fused corundum itself has extremely high hardness and wear resistance. By compounding part of gibbsite, the wear resistance of the prepared alumina ceramic is fundamentally guaranteed. Among them, gibbsite is thermally decomposed to form boehmite, and boehmite is transformed into different alumina transition phases, and finally turns into α-Al 2 O 3Taking diopside and calcium fluorosilicate as fluxes, diopside has the properties of a solvent and a strong mineralizer. By introducing diopside, a liquid phase is generated during the high-temperature sintering process. Under the action of surface tension, the liquid phase flows into the pores, reducing the porosity of the ceramic green body, increasing the density of the ceramic green body, and thus lowering the sintering temperature. The addition of calcium fluorosilicate can reduce the grain packing and sintering temperature, lower the viscosity of the glass phase, and promote the sintering of alumina ceramics at a lower temperature. Adding neodymium oxide, nickel aluminate, and strontium oxide as wear-resistant additives, the addition of neodymium oxide can affect the microstructure of alumina ceramics, reduce the content of the glass phase at the grain boundaries, effectively relieve the stress concentration at the grain boundaries caused by different thermal expansion coefficients. In addition, neodymium oxide promotes the formation of the second phase on the grain boundaries, reduces the micro-stress between grains and the probability of grain pull-out, thereby improving the wear resistance of the prepared alumina ceramics. Nickel aluminate has a spinel structure, with Al occupying the octahedral position and Ni occupying the tetrahedral position. It has excellent high-temperature stability, acid and alkali resistance, and wear resistance. By adding nickel aluminate, the fracture toughness and hardness of alumina ceramics are improved, so that the alumina ceramics do not crack when subjected to impact or stress, thereby improving their wear resistance. In addition, the addition of nickel aluminate can also change the wear mechanism of alumina ceramics, changing it from abrasive wear to adhesive wear, thereby reducing the wear rate of alumina ceramics. Under the action of high-temperature sintering, strontium oxide can form a solid solution with alumina. Through solid solution strengthening, the hardness and wear resistance of alumina ceramics are improved, and the fracture toughness of alumina ceramics is enhanced. Sodium tripolyphosphate in the raw materials acts as a wetting binder.

[0011] The preparation method of the microcrystalline wear-resistant alumina ceramic described in the present invention comprises the following steps:

[0012] (1) Mixing fused alumina powder, boehmite, diopside, calcium fluorosilicate, neodymium oxide, nickel aluminate, strontium oxide, and sodium tripolyphosphate evenly to obtain a mixture, and then performing wet ball milling and drying to prepare a powder material;

[0013] (2) Putting the powder material into a mold for pressing and forming, and then drying and firing to prepare a microcrystalline wear-resistant alumina ceramic.

[0014] Among them:

[0015] In step (1), when performing wet ball milling, the mass of water added accounts for 30-33% of the sum of the mass of the mixture and water, and the ball milling time is 40-41 h.

[0016] In step (1), the drying temperature is 105-108 °C, and the drying time is 7.5-7.7 h.

[0017] In step (2), the pressure for pressing and forming is 83-85 MPa.

[0018] In step (2), the drying temperature is 103 - 105 °C and the drying time is 4 - 4.2 h.

[0019] In step (2), the firing is carried out by heating to 730 - 750 °C at a rate of 3.5 °C / min, then heating to 1500 - 1520 °C at a rate of 2.2 °C / min and holding for 3.5 - 3.7 h, and finally cooling to room temperature with the furnace.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The microcrystalline wear-resistant alumina ceramic of the present invention uses fused corundum powder and gibbsite as the main raw materials, fundamentally ensuring the mechanical properties of the prepared alumina ceramic; uses diopside and calcium fluorosilicate as fluxes to reduce the firing temperature of the alumina ceramic and improve the density; uses neodymium trioxide, nickel aluminate and strontium oxide as wear-resistant additives, and utilizes the synergistic effect among the three to improve the wear resistance of the alumina ceramic by improving the microstructure of the alumina ceramic, avoiding stress concentration at grain boundaries and generating a second reinforcing phase. Thus, the raw materials interact with each other to ensure that the prepared alumina ceramic has excellent wear resistance while reducing the firing temperature.

[0022] (2) The preparation method of the microcrystalline wear-resistant alumina ceramic of the present invention has a simple process, easy-to-control parameters, is suitable for batch production, and the prepared alumina ceramic has high quality. Detailed Embodiments

[0023] The present invention will be further described below in conjunction with embodiments.

[0024] Embodiment 1

[0025] The microcrystalline wear-resistant alumina ceramic described in Embodiment 1 of the present invention is composed of the following raw materials in parts by weight: 82 parts of fused corundum powder, 18 parts of gibbsite, 0.5 part of diopside, 1.4 parts of calcium fluorosilicate, 0.12 part of neodymium trioxide, 1.3 parts of nickel aluminate, 0.13 part of strontium oxide, and 5.5 parts of sodium tripolyphosphate.

[0026] Among them:

[0027] The particle size of the fused corundum powder is 18 μm.

[0028] The preparation method of the microcrystalline wear-resistant alumina ceramic described in Embodiment 1 of the present invention consists of the following steps:

[0029] (1) Mix the fused corundum powder, gibbsite, diopside, calcium fluorosilicate, neodymium trioxide, nickel aluminate, strontium oxide and sodium tripolyphosphate evenly to obtain a mixture, and then carry out wet ball milling and drying to prepare a powder.

[0030] (2) Put the powder materials into a mold, press them into shape, and then dry and sinter them to prepare microcrystalline wear-resistant alumina ceramics.

[0031] Among them:

[0032] In step (1), when wet ball milling, the mass of water added accounts for 31% of the sum of the masses of the mixture and water, and the ball milling time is 40.5 h.

[0033] In step (1), the drying temperature is 106 °C and the drying time is 7.6 h.

[0034] In step (2), the pressure for pressing into shape is 84 MPa.

[0035] In step (2), the drying temperature is 104 °C and the drying time is 4.1 h.

[0036] In step (2), the sintering is carried out by heating to 740 °C at a rate of 3.5 °C / min, then heating to 1510 °C at a rate of 2.2 °C / min and holding for 3.6 h, and finally cooling to room temperature with the furnace.

[0037] The wear resistance of the microcrystalline wear-resistant alumina ceramics prepared in Example 1 is 12,000 revolutions, grade 5, the pollution resistance is grade 5, and the fracture toughness is 6.9 MPa·m 1 / 2 , where the wear resistance grading is tested according to GB / T 3810.7-2016, the pollution resistance is tested according to GB / T 3810.14-2016, and the fracture toughness is tested according to GB / T 23806-2009.

[0038] Example 2

[0039] The microcrystalline wear-resistant alumina ceramics described in this Example 2 are composed of the following raw materials in parts by weight: 80 parts of fused corundum powder, 20 parts of gibbsite, 0.4 part of diopside, 1.5 parts of calcium fluorosilicate, 0.1 part of neodymium sesquioxide, 1.4 parts of nickel aluminate, 0.1 part of strontium oxide, and 6 parts of sodium tripolyphosphate.

[0040] Among them:

[0041] The particle size of the fused corundum powder is 14 μm.

[0042] The preparation method of the microcrystalline wear-resistant alumina ceramics described in this Example 2 consists of the following steps:

[0043] (1) Mix the fused corundum powder, gibbsite, diopside, calcium fluorosilicate, neodymium sesquioxide, nickel aluminate, strontium oxide and sodium tripolyphosphate evenly to obtain a mixture, and then carry out wet ball milling and drying to prepare powder materials;

[0044] (2) Put the powder materials into a mold, press them into shape, and then dry and sinter them to prepare microcrystalline wear-resistant alumina ceramics.

[0045] Among them:

[0046] During wet ball milling in step (1), the mass of water added accounts for 33% of the sum of the masses of the mixture and water, and the ball milling time is 41 h.

[0047] In step (1), the drying temperature is 108 °C and the drying time is 7.5 h.

[0048] In step (2), the pressure for pressing and forming is 85 MPa.

[0049] In step (2), the drying temperature is 105 °C and the drying time is 4 h.

[0050] In step (2), the firing is carried out by heating to 750 °C at a rate of 3.5 °C / min, then heating to 1520 °C at a rate of 2.2 °C / min and holding for 3.7 h, and finally cooling to room temperature with the furnace.

[0051] The wear resistance of the microcrystalline wear-resistant alumina ceramic prepared in Example 2 is 12,000 revolutions, grade 5, the pollution resistance is grade 5, and the fracture toughness is 7.1 MPa·m 1 / 2 , where the wear resistance grading is tested according to GB / T 3810.7-2016, the pollution resistance is tested according to GB / T 3810.14-2016, and the fracture toughness is tested according to GB / T 23806-2009.

[0052] Example 3

[0053] The microcrystalline wear-resistant alumina ceramic described in this Example 3 is composed of the following raw materials in parts by weight: 83 parts of fused corundum powder, 17 parts of gibbsite, 0.6 part of diopside, 1.3 parts of calcium fluorosilicate, 0.13 part of neodymium sesquioxide, 1.2 parts of nickel aluminate, 0.15 part of strontium oxide, and 5 parts of sodium tripolyphosphate.

[0054] Among them:

[0055] The particle size of the fused corundum powder is 20 μm.

[0056] The preparation method of the microcrystalline wear-resistant alumina ceramic described in this Example 3 consists of the following steps:

[0057] (1) Mix the fused corundum powder, gibbsite, diopside, calcium fluorosilicate, neodymium sesquioxide, nickel aluminate, strontium oxide, and sodium tripolyphosphate evenly to obtain a mixture, and then carry out wet ball milling and drying to prepare a powder;

[0058] (2) Put the powder into a mold for pressing and forming, and then carry out drying and firing to prepare a microcrystalline wear-resistant alumina ceramic.

[0059] Among them:

[0060] In step (1), the mass of water added during wet ball milling accounts for 30% of the sum of the mass of the mixture and water, and the ball milling time is 40 h.

[0061] In step (1), the drying temperature is 105 °C and the drying time is 7.7 h.

[0062] In step (2), the pressure for pressing and forming is 83 MPa.

[0063] In step (2), the drying temperature is 103 °C and the drying time is 4.2 h.

[0064] In step (2), the firing is carried out by heating to 730 °C at a rate of 3.5 °C / min, then heating to 1500 °C at a rate of 2.2 °C / min and holding for 3.5 h, and finally cooling to room temperature with the furnace.

[0065] The wear resistance of the microcrystalline wear-resistant alumina ceramic prepared in Example 3 is 12,000 revolutions, grade 5, the pollution resistance is grade 5, and the fracture toughness is 6.8 MPa·m 1 / 2 , where the wear resistance grading is tested according to GB / T 3810.7-2016, the pollution resistance is tested according to GB / T3810.14-2016, and the fracture toughness is tested according to GB / T 23806-2009.

[0066] Comparative Example 1

[0067] The preparation method of the microcrystalline wear-resistant alumina ceramic described in this Comparative Example 1 is the same as that in Example 1, and the only difference is the raw material composition. The microcrystalline wear-resistant alumina ceramic described in this Comparative Example 1 is composed of the following raw materials in parts by weight: 82 parts of fused corundum powder, 18 parts of gibbsite, 0.5 part of diopside, 1.4 parts of calcium fluorosilicate, 1.3 parts of nickel aluminate, 0.13 part of strontium oxide, and 5.5 parts of sodium tripolyphosphate.

[0068] The wear resistance of the microcrystalline wear-resistant alumina ceramic prepared in Comparative Example 1 is 12,000 revolutions, grade 4, the pollution resistance is grade 4, and the fracture toughness is 5.1 MPa·m 1 / 2 , where the wear resistance grading is tested according to GB / T 3810.7-2016, the pollution resistance is tested according to GB / T3810.14-2016, and the fracture toughness is tested according to GB / T 23806-2009.

[0069] Comparative Example 2

[0070] The preparation method of the microcrystalline wear-resistant alumina ceramic described in Comparative Example 2 is the same as that in Example 1. The only difference lies in the raw material composition. The microcrystalline wear-resistant alumina ceramic described in Comparative Example 2 is composed of the following raw materials in parts by weight: 82 parts of fused corundum powder, 18 parts of gibbsite, 0.5 part of diopside, 1.4 parts of calcium fluorosilicate, 0.12 part of neodymium sesquioxide, 0.13 part of strontium oxide, and 5.5 parts of sodium tripolyphosphate.

[0071] The wear resistance of the microcrystalline wear-resistant alumina ceramic prepared in Comparative Example 2 is 12,000 revolutions, Grade 3, the pollution resistance is Grade 4, and the fracture toughness is 4.4 MPa·m 1 / 2 , where the wear resistance grading is tested according to GB / T 3810.7-2016, the pollution resistance is tested according to GB / T 3810.14-2016, and the fracture toughness is tested according to GB / T 23806-2009.

[0072] Comparative Example 3

[0073] The preparation method of the microcrystalline wear-resistant alumina ceramic described in Comparative Example 3 is the same as that in Example 1. The only difference lies in the raw material composition. The microcrystalline wear-resistant alumina ceramic described in Comparative Example 3 is composed of the following raw materials in parts by weight: 82 parts of fused corundum powder, 18 parts of gibbsite, 0.5 part of diopside, 1.4 parts of calcium fluorosilicate, 0.12 part of neodymium sesquioxide, 1.3 parts of nickel aluminate, and 5.5 parts of sodium tripolyphosphate.

[0074] The wear resistance of the microcrystalline wear-resistant alumina ceramic prepared in Comparative Example 3 is 12,000 revolutions, Grade 4, the pollution resistance is Grade 4, and the fracture toughness is 5.5 MPa·m 1 / 2 , where the wear resistance grading is tested according to GB / T 3810.7-2016, the pollution resistance is tested according to GB / T 3810.14-2016, and the fracture toughness is tested according to GB / T 23806-2009.

Claims

1. A microcrystalline wear-resistant alumina ceramic, characterized in that: The invention is composed of the following raw materials in parts by weight: 80-83 parts of fused corundum powder, 17-20 parts of gibbsite, 0.4-0.6 parts of diopside, 1.3-1.5 parts of calcium fluorosilicate, 0.1-0.13 parts of neodymium trioxide, 1.2-1.4 parts of nickel aluminate, 0.1-0.15 parts of strontium oxide and 5-6 parts of sodium tripolyphosphate.

2. The microcrystalline wear-resistant alumina ceramic according to claim 1, characterized in that: The particle size of fused corundum powder is 14-20μm.

3. A method for preparing the microcrystalline wear-resistant alumina ceramic according to claim 1, characterized in that: It consists of the following steps: (1) Evenly mixing fused corundum powder, gibbsite, diopside, calcium fluorosilicate, neodymium trioxide, nickel aluminate, strontium oxide and sodium tripolyphosphate to obtain a mixture, and then wet-ball milling and drying to obtain a powder; (2) The powder is placed in a mold and pressed into shape, and then dried and sintered to prepare microcrystalline wear-resistant alumina ceramics.

4. The method for preparing microcrystalline wear-resistant alumina ceramics according to claim 3, characterized in that: The mass of water added during wet ball milling in step (1) accounts for 30-33% of the mass of the mixture and water, and the ball milling time is 40-41 hours.

5. The method for preparing microcrystalline wear-resistant alumina ceramics according to claim 3, characterized in that: In step (1), the drying temperature is 105-108°C and the drying time is 7.5-7.7h.

6. The method for preparing microcrystalline wear-resistant alumina ceramics according to claim 3, characterized in that: The pressure of the pressing molding in step (2) is 83-85 MPa.

7. The method for preparing microcrystalline wear-resistant alumina ceramics according to claim 3, characterized in that: In step (2), the drying temperature is 103-105°C and the drying time is 4-4.2h.

8. The method for preparing microcrystalline wear-resistant alumina ceramics according to claim 3, characterized in that: The sintering in step (2) is performed by heating the temperature to 730-750°C at a rate of 3.5°C / min, then heating the temperature to 1500-1520°C at a rate of 2.2°C / min and keeping the temperature for 3.5-3.7h, and finally cooling the furnace to room temperature.