A high-hardness ceramic and its production process

Abstract

The invention discloses a high-hardness ceramic and a production process thereof, belonging to the technical field of ceramic manufacturing, wherein ZrO2 powder, nano ZrB2 powder dispersion, Al2O3 powder, and Y2O3 powder are mixed and ball-milled, dried, and passed through a 200-mesh sieve to obtain a ceramic powder; the ceramic powder is poured into a graphite mold for vacuum hot pressing sintering to obtain a high-hardness ceramic; the nano ZrB2 powder dispersion comprises the following steps of preparation: by weight, 1 part of polyvinyl pyrrolidone and 6-8 parts of polycarboxylic acid high-efficiency water reducer are added to 10-13 parts of water, 1.8-2.3 parts of nano ZrB2 powder are added after stirring and dissolving, and ultrasonic dispersion is performed for 10-15 minutes to obtain a nano ZrB2 powder dispersion. The present invention overcomes the agglomeration phenomenon of nano ZrB2 powder through the nano ZrB2 powder dispersion, and improves the hardness and high temperature wear resistance of the ceramic matrix.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic manufacturing, and in particular relates to a high-hardness ceramic and a production process thereof. Background Art

[0002] Cutting processing occupies an important position in the machinery manufacturing industry. With the widespread application of high-speed cutting processing technology and the emergence of a large number of difficult-to-process materials, the cutting force and cutting heat of existing ceramics in the actual cutting process have greatly increased, aggravating the wear of tool materials and bringing quality and safety risks. Therefore, the development of ceramics with good mechanical properties and friction reduction and wear resistance is the key to the development of high-performance cutting tools.

[0003] Zirconia ceramics are widely used in various industries as structural and functional materials, and are one of the high-performance new materials that are encouraged to develop in the national industrial policy. As a structural material, zirconia ceramics have been used to make high-performance ceramic cutting tools. However, zirconia ceramics have a crystal structure with ionic and covalent bonds as bonding bonds, which makes zirconia ceramics have common disadvantages of ceramic materials such as severe tool wear.

[0004] Zirconia ceramics need to have excellent wear resistance, and higher hardness is the guarantee of excellent wear resistance. Therefore, it is necessary to develop a high-hardness ceramic and its production process. Summary of the invention

[0005] The purpose of the present invention is to provide a high-hardness ceramic and a production process thereof to solve the following technical problem: improving the hardness of zirconia ceramics.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A production process of high hardness ceramics, comprising the following steps:

[0008] Step S1: ZrO2 powder, nano ZrB2 powder dispersion, Al2O3 powder and Y2O3 powder are mixed to obtain a mixed powder; the mixed powder, grinding balls and anhydrous ethanol as a ball milling medium are added to a ball mill, and the mixed powder is ball milled at a speed of 160-200 r / min for 3-4 hours, dried at 60°C for 3-4 hours, and passed through a 200-mesh sieve to obtain a ceramic powder;

[0009] Step S2: pouring the ceramic powder into a graphite mold and performing vacuum hot pressing sintering to obtain a high-hardness ceramic;

[0010] The nano ZrB2 powder dispersion comprises the following steps for preparation:

[0011] By weight, add 3-4 parts of dispersant to 8-10 parts of water, stir to dissolve, then add 1.8-2.3 parts of nano ZrB2 powder, and ultrasonically disperse for 10-15min to obtain a nano ZrB2 powder dispersion;

[0012] The dispersant comprises the following steps of preparation:

[0013] Add octadecyl acrylate into a reaction vessel, heat in a water bath to 80°C and maintain a constant temperature, stir and simultaneously add dropwise methacrylic acid and an aqueous solution of ammonium persulfate with a concentration of 2.5-3 g / mL, react for 4 hours after the addition is complete, cool, adjust the pH to 7, wash with anhydrous ethanol, filter, dry, and grind for 24 hours to obtain a dispersant.

[0014] As a further solution of the present invention, the mass ratio of the ZrO2 powder, nano ZrB2 powder dispersion, Al2O3 powder and Y2O3 powder is 87-92: 2.1-3.5: 4.2-9.5: 4.0-6.5.

[0015] As a further solution of the present invention, a layer of 0.3 mm graphite paper is placed between the graphite mold and the ceramic powder in step S2 to prevent the graphite mold from sticking to the ceramic and to facilitate demoulding.

[0016] As a further solution of the present invention, the ball mill and the grinding balls of the ball mill are both made of ZrO2. The mass ratio of the mixed powder, the grinding balls and the anhydrous ethanol is 1-2:2:4.

[0017] As a further solution of the present invention, the sintering temperature of the vacuum hot pressing sintering is 1350-1550°C, the heating rate is 5-10°C / min, the holding time is 0.5-1h, and the sintering pressure is 30MPa.

[0018] As a further embodiment of the present invention, the usage ratio of octadecyl acrylate, methacrylic acid and aqueous ammonium persulfate is 2-3 g:10-12 g:7-10 mL.

[0019] A high-hardness ceramic is prepared by the production process.

[0020] Beneficial effects of the present invention:

[0021] The invention obtains a dispersant by polymerizing octadecyl acrylate and methacrylic acid under the action of an initiator, ammonium persulfate, and then dissolving the dispersant in water and mixing it with nano ZrB2 powder for ultrasonic dispersion to obtain a nano ZrB2 powder dispersion. The dispersant has both hydrophilic and hydrophobic groups in its molecular formula, and has good attraction to hydrophilic and hydrophobic substances. The hydrophobic groups in the molecular structure of the dispersant and the hydrophobic surface of the nano ZrB2 powder attract each other, and can resist the van der Waals force between the nano ZrB2 powders, thereby maintaining the uniform stability of the dispersion and preventing the nano ZrB2 powders from agglomerating. Meanwhile, the anionic carboxyl units of the dispersant also help to increase the electrostatic repulsion between the nano ZrB2 powders, thereby further improving the dispersibility thereof. The invention overcomes the agglomeration phenomenon of the nano ZrB2 powder through the nano ZrB2 powder dispersion, and can make the nano ZrB2 powder more uniformly dispersed in the ZrO2 ceramic matrix, thereby improving the hardness and high temperature wear resistance of the ceramic matrix by utilizing the high hardness and thermal stability of ZrB2. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Example 1

[0024] A nano ZrB2 powder dispersion comprises the following steps of preparation:

[0025] Step 1: Add 2 g of octadecyl acrylate into a reaction vessel, heat it in a water bath to 80° C. and keep the temperature constant, stir and simultaneously drop 10 g of methacrylic acid and 7 mL of an aqueous solution of ammonium persulfate with a concentration of 2.5 g / mL, react for 4 h after the dropwise addition is completed, cool, adjust the pH to 7, wash with anhydrous ethanol, filter, dry, and grind for 24 h to obtain a dispersant;

[0026] Step 2: Add 3 g of dispersant into 8 g of water, stir to dissolve, then add 1.8 parts of nano ZrB2 powder, and disperse by ultrasonic for 10 min to obtain nano ZrB2 powder dispersion.

[0027] Example 2

[0028] A nano ZrB2 powder dispersion comprises the following steps of preparation:

[0029] Step 1: Add 3 g of octadecyl acrylate into a reaction vessel, heat it in a water bath to 80° C. and keep the temperature constant, stir and simultaneously drop 12 g of methacrylic acid and 10 mL of a 3 g / mL aqueous solution of ammonium persulfate, react for 4 h after the addition is complete, cool, adjust the pH to 7, wash with anhydrous ethanol, filter, dry, and grind for 24 h to obtain a dispersant;

[0030] Step 2: Add 4 g of dispersant into 10 g of water, stir to dissolve, then add 2.3 parts of nano ZrB2 powder, and perform ultrasonic dispersion for 15 min to obtain nano ZrB2 powder dispersion.

[0031] Comparative Example 1

[0032] A nano ZrB2 powder dispersion comprises the following steps of preparation:

[0033] Add 1.8 parts of nano ZrB2 powder to 8 g of water and disperse by ultrasonic for 10 min to obtain a nano ZrB2 powder dispersion.

[0034] Example 3

[0035] A production process of high hardness ceramics, comprising the following steps:

[0036] Step S1: 87g ZrO2 powder, 2.1g nano ZrB2 powder dispersion prepared in Example 1, 4.2g Al2O3 powder, and 4.0g Y2O3 powder are mixed to obtain a mixed powder; 100g of the mixed powder, 200g ZrO2 grinding balls, and 400g of anhydrous ethanol as a ball milling medium are added to a ZrO2 ball mill, and the mixture is mixed and ball milled at a speed of 160r / min for 3h, dried at 60°C for 3h, and passed through a 200-mesh sieve to obtain a ceramic powder;

[0037] Step S2: After placing a layer of 0.3 mm graphite paper between the graphite mold and the ceramic powder, pour the ceramic powder into the graphite mold for vacuum hot pressing sintering. The sintering temperature of the vacuum hot pressing sintering is 1350°C, the heating rate is 5°C / min, the insulation time is 0.5h, and the sintering pressure is 30MPa, to obtain a high hardness ceramic.

[0038] Example 4

[0039] A production process of high hardness ceramics, comprising the following steps:

[0040] Step S1: 92g ZrO2 powder, 3.5g nano ZrB2 powder dispersion prepared in Example 2, 9.5g Al2O3 powder, and 6.5g Y2O3 powder are mixed to obtain a mixed powder; 200g of the mixed powder, 200g ZrO2 grinding balls, and 400g of anhydrous ethanol as a ball milling medium are added to a ZrO2 ball mill, and the mixture is mixed and ball milled at a speed of 200r / min for 4h, dried at 60°C for 4h, and passed through a 200-mesh sieve to obtain a ceramic powder;

[0041] Step S2: After a layer of 0.3 mm graphite paper is placed between the graphite mold and the ceramic powder, the ceramic powder is poured into the graphite mold for vacuum hot pressing sintering. The sintering temperature of the vacuum hot pressing sintering is 1550°C and the heating rate is 10°C / min. -1 , holding time is 1h, sintering pressure is 30MPa, and a high hardness ceramic is obtained.

[0042] Comparative Example 2

[0043] A production process of high hardness ceramics, comprising the following steps:

[0044] Step S1: 87g ZrO2 powder, 2.1g nano ZrB2 powder dispersion prepared in Comparative Example 1, 4.2g Al2O3 powder, and 4.0g Y2O3 powder are mixed to obtain a mixed powder; 100g of the mixed powder, 200g ZrO2 grinding balls, and 400g of anhydrous ethanol as a ball milling medium are added to a ZrO2 ball mill, and the mixture is mixed and ball milled at a speed of 160r / min for 3h, dried at 60°C for 3h, and passed through a 200-mesh sieve to obtain a ceramic powder;

[0045] Step S2: After placing a layer of 0.3 mm graphite paper between the graphite mold and the ceramic powder, pour the ceramic powder into the graphite mold for vacuum hot pressing sintering. The sintering temperature of the vacuum hot pressing sintering is 1350°C, the heating rate is 5°C / min, the insulation time is 0.5h, and the sintering pressure is 30MPa, to obtain a high hardness ceramic.

[0046] Compared with Example 3, this comparative example only replaces "2.1 g of nano ZrB2 powder dispersion prepared in Example 1" with "2.1 g of nano ZrB2 powder dispersion prepared in Comparative Example 1", and the remaining steps and parameters are the same.

[0047] The performance tests were performed on the ceramics obtained in Examples 3-4 and Comparative Example 2:

[0048] 1. According to GB / T 16534-2009, the Vickers hardness was measured using a microhardness test and analysis system (HVST-1000C, Shanghai Zhongyan Instrument Manufacturing Plant, China) with a load of 4.903 N and a loading time of 15 s (the measurement was repeated 5 times and the arithmetic mean was taken);

[0049] 2. Measure the wear resistance coefficient according to ISO 6474;

[0050] The test results are shown in Table 1.

[0051] Table 1

[0052] project Example 3 Example 4 Comparative Example 2 Vickers hardness / HV 2420 2450 1780 Wear resistance coefficient (1200℃, rotation) 15400 15466 11500

[0053] It can be seen from Table 1 that the ceramics prepared in Examples 3-4 of the present invention have higher hardness and high temperature wear resistance than the ceramics prepared in Comparative Example 2.

[0054] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0055] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A production process for high hardness ceramics, characterized in that: The steps include: Step S1: ZrO2 powder, nano ZrB2 powder dispersion, Al2O3 powder and Y2O3 powder are mixed to obtain a mixed powder; the mixed powder, grinding balls and anhydrous ethanol are added to a ball mill, and the mixed powder is ball milled at a speed of 160-200 r / min for 3-4 hours, dried at 60° C. for 3-4 hours, and passed through a 200-mesh sieve to obtain a ceramic powder; Step S2: pouring the ceramic powder into a graphite mold and performing vacuum hot pressing sintering to obtain a high-hardness ceramic; The nano ZrB2 powder dispersion comprises the following steps for preparation: By weight, add 3-4 parts of dispersant to 8-10 parts of water, stir to dissolve, then add 1.8-2.3 parts of nano ZrB2 powder, and ultrasonically disperse for 10-15 minutes to obtain a nano ZrB2 powder dispersion; The dispersant comprises the following steps of preparation: Add octadecyl acrylate to a reaction vessel, heat in a water bath to 80°C and maintain a constant temperature, add methacrylic acid and an aqueous solution of ammonium persulfate with a concentration of 2.5-3 g / mL while stirring, react for 4 hours after the addition is complete, cool, adjust the pH to 7, wash with anhydrous ethanol, filter, dry, and grind for 24 hours to obtain a dispersant; The mass ratio of the ZrO2 powder, nano ZrB2 powder dispersion, Al2O3 powder and Y2O3 powder is 87-92: 2.1-3.5：4.2-9.5：4.0-6.5； A layer of 0.3 mm graphite paper is placed between the graphite mold and the ceramic powder; The ball mill and grinding balls of the ball mill are both made of ZrO2, and the mass ratio of the mixed powder, grinding balls and anhydrous ethanol is 1-2:2:4; The sintering temperature of the vacuum hot pressing sintering is 1350-1550°C, the heating rate is 5-10°C / min, the holding time is 0.5-1h, and the sintering pressure is 30MPa; The usage ratio of octadecyl acrylate, methacrylic acid and ammonium persulfate water solution is 2-3g:10-12g:7-10mL.

2. A high hardness ceramic, characterized in that: The method is prepared by the production process described in claim 1.