A low thermal expansion composite ceramic tool material, preparation process and tool

Abstract

The invention discloses a low thermal expansion composite ceramic tool material, a preparation process thereof and a tool, which is composed of the following components by volume: 1 to 40 parts of negative thermal expansion material or low thermal expansion material, 1 to 3 parts of sintering aid, 10 to 20 parts of toughening and reinforcing material, and the balance is matrix material; the negative thermal expansion material or low thermal expansion material is selected from LiAlSiO4, Mg2Al4Si5O 18 and ZrW2O8 or a combination thereof. The prepared low expansion ceramic tool has lower thermal expansion performance while improving the fracture toughness and bending strength of the tool, thereby improving the overall thermal shock resistance of the ceramic tool to achieve higher processing quality and service life.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic tool machining, and in particular relates to a low thermal expansion composite ceramic tool material, a preparation process thereof and a tool. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Ceramic cutting tools have high red hardness and wear resistance, and are one of the important tools used for cutting in mechanical manufacturing tools. Ceramic cutting tools used in mechanical manufacturing are basically used to cut metal materials, so the research on the materials that make up the cutting tools is a very important task. By changing the material components in the ceramic cutting tools, different types of materials can be cut and processed, the service life of the cutting tools can be improved, and the processing efficiency and the surface quality of the workpiece being processed can be improved. However, existing ceramic cutting tools encounter problems of brittle damage and thermal stress caused by continuous or intermittent processing when cutting difficult-to-process materials.

[0004] At present, ceramic cutting tools are not made of a single material, but a composite material composed of a combination of multiple materials. Compared with ordinary materials, composite materials have many characteristics that can improve or optimize the shortcomings of a single material, fully demonstrate the advantages of a single material, and give composite materials new properties. However, composite materials also have some disadvantages. Different materials have different properties, and one of the most important properties is thermal expansion. Thermal expansion refers to the fact that when the external pressure remains unchanged, the volume of most materials increases as the temperature increases, and the volume decreases when the temperature decreases. When the thermal expansion coefficient of the tool material is large, it cannot meet the requirements of precision machining and ultra-precision machining with high dimensional accuracy.

[0005] In addition, the thermal shock resistance of ceramic materials refers to an important indicator for evaluating their ability to resist breakage when subjected to drastic temperature changes. When the thermal expansion coefficient of the tool material is high, its thermal shock resistance is weak and it is difficult to withstand drastic temperature changes. Summary of the invention

[0006] In order to reduce the influence of thermal expansion performance of ceramic tool materials during preparation or processing, thereby improving the overall hardness, fracture toughness and bending strength of the tool, and improving the thermal shock resistance of the ceramic tool. The present invention proposes a low thermal expansion composite ceramic tool material, its preparation process and tool. The low expansion ceramic tool prepared by a special process method has lower thermal expansion performance while improving the fracture toughness and bending strength of the tool, and improves the overall thermal shock resistance of the ceramic tool to achieve higher processing quality and service life.

[0007] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0008] In a first aspect, the present invention provides a low thermal expansion ceramic tool material, which is composed of the following components by volume: 1 to 40 parts of negative thermal expansion material or low thermal expansion material, 1 to 3 parts of sintering aid, 10 to 20 parts of toughening and reinforcing material, and the balance is matrix material;

[0009] The negative thermal expansion material or low thermal expansion material is selected from LiAlSiO 4 Mg 2 Al 4 Si 5 O 18 and ZrW 2 O 8 One or a combination of the following.

[0010] When the negative thermal expansion material is ZrW 2 O 8 In order to obtain composite ceramics with better mechanical properties, on the one hand, by adding a certain proportion of sintering aids, such as MgO and Y 2 O 3 On the other hand, the sintering temperature of the composite material can be adjusted during the preparation process. 2 O 3 , ZrW 2 O 8 、SiC w , Y 2 O 3 In the system of composite materials of Ag and MgO, a composite ceramic material with excellent mechanical properties was prepared by controlling the sintering temperature of vacuum hot pressing to 1400-1700°C.

[0011] The present invention selects LiAlSiO 4 and ZrW 2 O 8 It is a negative thermal expansion material, Mg 2 Al 4 Si 5 O 18 It is a low thermal expansion material. By adding a low or negative thermal expansion phase to the preparation of a composite material, the overall thermal expansion coefficient of the composite material can be controlled to obtain a lower or near-zero or negative thermal expansion material. By reducing the overall thermal expansion coefficient of the composite material, the thermal stress caused by temperature changes in the material can be reduced, the material's ability to resist thermal shock can be enhanced, and the thermal shock resistance and service life of ceramic tools can be improved.

[0012] In some embodiments, the sintering aid is selected from MgO, Y 2 O 3 Sc 2 O 3 , Cr, Ni or a combination thereof.

[0013] In some embodiments, the toughening and reinforcing material is selected from SiC p 、SiC w , TiC, WC or a combination thereof.

[0014] In some embodiments, the matrix material is selected from Al 2 O 3 、Sialon、Si 3 N 4 One or a combination of the following.

[0015] In a second aspect, the present invention provides a method for preparing the low thermal expansion ceramic tool material, comprising the following steps:

[0016] The base material, the negative thermal expansion material or the low thermal expansion material, and the sintering aid toughening and reinforcing material are separately ball-milled to obtain a single-phase powder;

[0017] The single-phase powders are mixed and ball-milled in proportion, and the suspension after ball milling is dried, sieved and packaged to obtain a low thermal expansion ceramic tool material.

[0018] In some embodiments, in single ball milling and / or mixed ball milling, the ball milling time is 48h to 72h; the ball-to-material ratio is 5:1 to 10:1; the ball mill speed is 250r / min to 400r / min; and the mass ratio of anhydrous ethanol to powder is 1:1 to 2:1.

[0019] By adjusting the ball milling time, ball mill speed, ball milling media, and ball milling each raw material separately and then mixing them together, the powder material can be made more uniform and powder agglomeration can be effectively avoided to ensure that the tool material performance meets the requirements.

[0020] In some embodiments, the drying is vacuum drying, the drying temperature is 80-140° C., and the drying time is greater than 5 hours. Appropriate drying temperature and sufficient drying time can ensure that the powder is sufficiently dry, reduce powder agglomeration, and be more conducive to sieve screening.

[0021] In a third aspect, the present invention provides a low thermal expansion ceramic tool, which is made by pre-pressing the low thermal expansion ceramic tool material into a green body and then sintering the green body.

[0022] In some embodiments, the sintering is vacuum hot pressing sintering or spark plasma sintering.

[0023] Preferably, the vacuum hot pressing sintering procedure is:

[0024] In the first stage, the temperature is raised to 1000-1200°C at a first heating rate of 10-50°C / min, and the pressure is increased linearly during the same period until it reaches 10-15MPa, and then the temperature and pressure are maintained for 5-10 minutes;

[0025] In the second stage, the temperature is raised to 1400-1700°C at a second heating rate of 10-30°C / min, and the pressure is increased linearly during the same period until it reaches 30-40MPa, and then the temperature and pressure are maintained for 30-60min;

[0026] In the third stage, after heat and pressure maintenance, the sintered body is air-cooled with the furnace, and the pressure is released linearly until the pressure reaches several MPa and remains unchanged.

[0027] Preferably, the procedure of spark plasma sintering is:

[0028] In the first stage, the temperature is raised to 600-800°C at a first heating rate of 100-200°C / min, and the pressure is increased linearly during the same period until it reaches 10-15MPa;

[0029] In the second stage, the temperature is raised to 1400-1700°C at a second heating rate of 50-150°C / min, and the pressure is increased linearly during the same period until it reaches 30-40MPa, and the temperature and pressure are maintained for 5-15min;

[0030] In the third stage, after heat and pressure maintenance, the sintered body is air-cooled with the furnace, and the pressure is released linearly until the pressure reaches several MPa and remains unchanged.

[0031] In some embodiments, the pre-pressing pressure is greater than 3 MPa, and the pre-pressing time is not less than 30 minutes. Appropriate pressure and sufficient pre-pressing time are beneficial to the green body forming and the sintering of the ceramic composite material.

[0032] The beneficial effects achieved by one or more embodiments of the present invention are as follows:

[0033] At present, ceramic cutting tools have higher mechanical properties, but ceramics are more brittle than metals and are more sensitive to crack propagation caused by stress concentration. When subjected to thermal shock, due to the different thermal expansion coefficients between the materials, the thermal stress generated causes the crack propagation to intensify, and eventually leads to the destruction of the ceramic composite cutting tool. The present invention adds a near-zero or negative thermal expansion material to the ceramic composite material, and after sintering, a low thermal expansion multi-component composite ceramic material is obtained, which has higher mechanical properties and can be applied to cutting processing, and has a lower thermal expansion coefficient, which can improve the thermal shock resistance and service life of the cutting tool material. The low thermal expansion composite material has simple constituent materials, a convenient preparation method, a low sintering temperature, a short preparation time, a low production cost, and resource saving, and can ensure that the obtained ceramic composite material has a lower thermal expansion coefficient.

[0034] This low thermal expansion multi-component composite ceramic tool has a simple structure, a low thermal expansion coefficient, high hardness, fracture toughness and bending strength, and can be well applied to mechanical cutting processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0036] Figure 1 It is a process flow chart of composite powder preparation according to an embodiment of the present invention.

[0037] Figure 2 It is a vacuum hot pressing sintering process diagram of an embodiment of the present invention.

[0038] Figure 3 It is a spark plasma sintering process diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0039] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0040] The present invention will be further described below in conjunction with the embodiments.

[0041] Example 1

[0042] The powder volume fraction ratio (vol.%) required to prepare a low thermal expansion multi-component composite ceramic tool material is shown in Table 1.

[0043] Table 1 Composite powder volume ratio (vol.%)

[0044] <![CDATA[Al 2 THE 3 ]]> <![CDATA[LiAlSiO 4 ]]> <![CDATA[SiC w ]]> MgO <![CDATA[Y 2 THE 3 ]]> Ni the remaining 30 15 2 1 0.5

[0045] (1) First ball milling: Al 2 O 3 Powder, LiAlSiO 4 Powder, SiCw powder, MgO powder, Y 2 O 3 The powder and Ni powder were placed in a polyurethane ball mill, and alumina grinding balls of different particle sizes were added at a ball-to-material ratio of 8:1, and anhydrous ethanol was added at a ball-to-powder mass ratio of 2:1. A planetary ball mill was used for high-speed ball milling, and the ball milling process adopted bidirectional ball milling, with the ball milling direction being reversed every 30 minutes. The total ball milling time was 72 hours, and the ball milling speed was set to 300r / min.

[0046] (2) First drying: Pour the milled suspension into beakers and place them in a drying oven. The drying process is vacuum drying, the drying time is 5 hours, and the temperature is 110°C. The dried powder is passed through a 200-mesh stainless steel sieve, and the powder passing through the sieve is sealed and stored to obtain a single-phase powder.

[0047] (3) Weighing: Convert the volume fraction ratio of the composite powder into the mass fraction ratio, and weigh 51.5 vol% Al after ball milling. 2 O 3 Powder, 30 vol% LiAlSiO 4 Powder, 15 vol% SiC w Powder, 2vol% MgO powder, 1vol% Y 2 O 3 Powder, 0.5 vol% Ni powder.

[0048] (4) Second ball milling: The weighed powders were mixed into a ball milling jar, and alumina grinding balls were added at a ball-to-material ratio of 5:1. Anhydrous ethanol was added at a ball-to-powder mass ratio of 1:1. A planetary ball mill was used for high-speed ball milling. The ball milling process adopted bidirectional ball milling, and the direction was reversed every 15 minutes. The total ball milling time was 48 hours, and the ball milling speed was set to 300 r / min.

[0049] (5) Second drying: Pour the milled suspension into beakers and place them in a drying oven. The drying process is vacuum drying, the drying time is 5 hours, and the temperature is 120° C. The dried powder is passed through a 200-mesh sieve, and the powder that passes through the sieve is sealed and stored to obtain a composite powder.

[0050] The composite powder preparation process of the above low thermal expansion multi-component composite ceramic tool material is as follows Figure 1 shown.

[0051] (6) Molding: Weigh an appropriate amount of composite powder, pour the powder into a graphite mold, and pre-press it into a round cake body using a hydraulic jack. The pre-pressing pressure is 5 MPa and the pre-pressing time is 30 min.

[0052] (7) The pre-pressed mold is placed in a sintering furnace and a vacuum hot pressing sintering process is used. The vacuum degree in the furnace must be kept below 0.01 MPa. In the first stage, the temperature is raised to 1000°C at a first heating rate of 15°C / min, and the pressure is increased linearly during the same period. After reaching 15 MPa, the pressure is kept constant and kept at this temperature for 5 minutes. In the second stage, the temperature is raised to 1600°C at a second heating rate of 10°C / min, and the pressure is increased linearly during the same period. After reaching 30 MPa, the pressure is kept constant and kept at this temperature for 30 minutes. In the third stage, after the end of the heat preservation and pressure holding, the sintered body is air-cooled with the furnace, and the pressure is released linearly at 1 MPa / min until the pressure reaches several MPa. Finally, a low thermal expansion multi-component composite ceramic tool material is obtained.

[0053] The vacuum hot pressing sintering process of the above low thermal expansion multi-component composite ceramic tool materials is as follows Figure 2 shown.

[0054] Example 2

[0055] The powder volume fraction ratio (vol.%) required to prepare a low thermal expansion multi-component composite ceramic tool material is shown in Table 2.

[0056] Table 2 Composite powder volume ratio (vol.%)

[0057] <![CDATA[Si 3 N 4 ]]> <![CDATA[Mg 2 the 4 And 5 A 18 ]]> <![CDATA[Al 2 THE 3 ]]> MgO <![CDATA[Y 2 THE 3 ]]> Ni the remaining 35 15 1 3 0.5

[0058] This embodiment is the same as embodiment 1, except that the material components and masses in the first ball milling and weighing are different.

[0059] The sintering process is as follows: the spark plasma sintering process is used for sintering, and the vacuum degree in the furnace needs to be ensured to be less than 0.01MPa. In the first stage, the temperature is raised to 800℃ at the first heating rate of 150℃ / min, and the pressure is increased linearly in the same period, and the pressure is kept constant after reaching 15MPa; in the second stage, the temperature is raised to 1550℃ at the second heating rate of 100℃ / min, and the pressure is increased linearly in the same period, and the pressure is kept constant after reaching 30MPa, and the heat and pressure are maintained for 5min; in the third stage, after the heat and pressure are maintained, the sintered body is air-cooled with the furnace, and the pressure is released linearly at 1MPa / min until the pressure stops at several MPa. Finally, a low thermal expansion multi-component composite ceramic tool material is obtained.

[0060] The spark plasma sintering process of the above low thermal expansion multi-component composite ceramic tool materials is as follows Figure 3 shown.

[0061] Example 3

[0062] The powder volume fraction ratio (vol.%) required to prepare a low thermal expansion multi-component composite ceramic tool material is shown in Table 3.

[0063] Table 3 Volume ratio of composite powder (vol.%)

[0064] <![CDATA[Al 2 THE 3 ]]> <![CDATA[ZrW 2 THE 8 ]]> TiN MgO <![CDATA[Sc 2 THE 3 ]]> Co the remaining 30 20 2 1 0.5

[0065] This embodiment is the same as embodiment 1, except that the material components and masses in the first ball milling and weighing are different.

[0066] The sintering process is as follows: the pre-pressed mold is placed in a sintering furnace, and a vacuum hot pressing sintering process is used. The vacuum degree in the furnace must be kept below 0.01 MPa. In the first stage, the temperature is raised to 1000°C at a first heating rate of 15°C / min, and the pressure is increased linearly during the same period. After reaching 15MPa, the pressure is kept constant and kept warm for 5 minutes; in the second stage, the temperature is raised to 1450°C at a second heating rate of 10°C / min, and the pressure is increased linearly during the same period. After reaching 30MPa, the pressure is kept constant and kept warm for 30 minutes; in the third stage, after the insulation and pressure are completed, the sintered body is air-cooled with the furnace, and the pressure is released linearly at 1MPa / min until the pressure stops at several MPa. Finally, a low thermal expansion multi-component composite ceramic tool material is obtained.

[0067] Example 4

[0068] The powder volume fraction ratio (vol.%) required to prepare a low thermal expansion multi-component composite ceramic tool material is shown in Table 4.

[0069] Table 4 Volume ratio of composite powder (vol.%)

[0070] Sialon <![CDATA[LiAlSiO 4 ]]> <![CDATA[Mg 2 the 4 And 5 A 18 ]]> <![CDATA[SiC w ]]> MgO <![CDATA[Sc 2 THE 3 ]]> the remaining 20 15 15 1 3

[0071] This embodiment is the same as embodiment 1, except that the material components and masses in the first ball milling and weighing are different.

[0072] Example 5

[0073] 69 parts Al 2 O 3 、15 parts LiAlSiO 4 , 15 parts of SiC whiskers, 1 part of MgO, and were prepared by vacuum hot pressing sintering process at a sintering temperature of 1400° C. The other process parameters were the same as those in Example 1.

[0074] Example 6

[0075] 67 parts Si 3 N 4 、10 parts Mg 2 Al 4 Si 5 O 18 , 20 parts SiC whiskers, 3 parts Y 2 O3 , it is prepared by vacuum hot pressing sintering process at a sintering temperature of 1600°C, and the other process parameters are the same as those in Example 1.

[0076] Example 7

[0077] 69 parts Al 2 O 3 、15 parts Mg 2 Al 4 Si 5 O 18 , 15 parts of SiC whiskers, 1 part of MgO, and are prepared by vacuum hot pressing sintering process at a sintering temperature of 1400°C. The other process parameters are the same as those in Example 1.

[0078] Example 8

[0079] 67 parts Al 2 O 3 , 15 copies of ZrW 2 O 8 , 15 parts SiC whiskers, 1 part MgO, 2 parts Y 2 O 3 , it is prepared by vacuum hot pressing sintering process at a sintering temperature of 1400°C, and other process parameters are the same as those in Example 1.

[0080] Table 5 Mechanical properties and linear expansion coefficients of ceramic materials of various embodiments of the present invention

[0081]

[0082] In summary, the ceramic composite material obtained in the present application has excellent and uniform near-zero expansion performance, good dimensional stability, good bending resistance and toughness, and is suitable for wide use.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A low thermal expansion ceramic tool, characterized in that: The low thermal expansion ceramic tool is made by pre-pressing a low thermal expansion ceramic tool material into a green body, and then sintering the green body; The low thermal expansion ceramic tool material is composed of the following components by volume: 1 to 40 parts of negative thermal expansion material or low thermal expansion material, 1 to 3 parts of sintering aid, 10 to 20 parts of toughening and reinforcing material, and the remainder is matrix material; The negative thermal expansion material or low thermal expansion material is selected from LiAlSiO4, Mg2Al4Si5O 18 One or a combination of the following: The matrix material is selected from one of Sialon and Si3N4 or a combination thereof; The method for preparing the low thermal expansion ceramic tool material comprises the following steps: The base material, the negative thermal expansion material or the low thermal expansion material, the sintering aid, and the toughening and reinforcing material are ball-milled separately to obtain a single-phase powder; The single-phase powders are mixed and ball-milled in proportion, and the suspension after ball milling is dried, sieved, and packaged to obtain a low thermal expansion ceramic tool material; The sintering is vacuum hot pressing sintering or spark plasma sintering; The procedure of the vacuum hot pressing sintering is: In the first stage, the temperature is raised to 1000-1200°C at a first heating rate of 10-50°C / min, and the pressure is increased linearly during the same period until it reaches 10-15MPa, and then the temperature and pressure are maintained for 5-10 minutes; In the second stage, the temperature is raised to 1400-1700°C at a second heating rate of 10-30°C / min, and the pressure is increased linearly during the same period until it reaches 30-40MPa, and then the temperature and pressure are maintained for 30-60min; In the third stage, after heat and pressure maintenance, the sintered body is air-cooled with the furnace, and the pressure is released linearly until the pressure reaches several MPa and remains constant; The procedure of spark plasma sintering is: In the first stage, the temperature is raised to 600-800°C at a first heating rate of 100-200°C / min, and the pressure is increased linearly during the same period until it reaches 10-15MPa; In the second stage, the temperature is raised to 1400-1700°C at a second heating rate of 50-150°C / min, and the pressure is increased linearly during the same period until it reaches 30-40MPa, and the temperature and pressure are maintained for 5-15min; In the third stage, after heat and pressure maintenance, the sintered body is air-cooled with the furnace, and the pressure is released linearly until the pressure reaches several MPa and remains unchanged.

2. The low thermal expansion ceramic tool according to claim 1, characterized in that: The sintering aid is selected from one of MgO, Y2O3, Sc2O3, Cr, Ni or a combination thereof.

3. The low thermal expansion ceramic tool according to claim 1, characterized in that: The toughening and reinforcing material is selected from SiC p 、SiC w , TiC, WC or a combination thereof.

4. The low thermal expansion ceramic tool according to claim 1, characterized in that: In single ball milling and / or mixed ball milling, the ball milling time is 48h~72h; the ball-to-material ratio is 5:1~10:1; the ball mill speed is 250r / min~400r / min; the mass ratio of anhydrous ethanol to powder is 1:1~2:

1.

5. The low thermal expansion ceramic tool according to claim 1, characterized in that: The drying is vacuum drying, the drying temperature is 80-140° C., and the drying time is greater than 5 hours.

6. The low thermal expansion ceramic tool according to claim 1, characterized in that: The pre-pressing pressure is greater than 3MPa, and the pre-pressing time is not less than 30min.

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