Alumina-based ceramic cutting tool and preparation method thereof

Abstract

The invention relates to the technical field of cutting tools, and provides an alumina-based ceramic cutting tool and a preparation method thereof. A salt solution of nickel nitrate and yttrium nitrate is ball-milled and mixed with Al2O3, so that yttrium ions and nickel ions can be well coated on the surface of Al2O3, and then a Ni-Y2O3-Al2O3 composite powder uniformly coated with metal Ni and Y2O3 can be prepared by decomposing the salt solution mixture and reducing the decomposition product with H2. The composite powder can be directly ball-milled and mixed with TiC powder to prepare an alumina-based ceramic cutting tool with uniform organizational structure, high relative density, good hardness and fracture toughness.

Description

Technical Field

[0001] The invention belongs to the technical field of cutting tools, and in particular relates to an alumina-based ceramic cutting tool and a preparation method thereof. Background Art

[0002] Al2O3 ceramics are widely used in the fields of machinery, electronics, chemical industry, etc. due to their excellent properties such as high strength, high hardness, high wear resistance, oxidation resistance and thermal shock resistance. Pure Al2O3 ceramics have good high temperature performance, but insufficient toughness, poor impact resistance, and are prone to slight chipping during cutting. This phenomenon can be significantly improved by adding toughening materials to the Al2O3 matrix.

[0003] Adding certain carbides to Al2O3 can improve the strength and impact resistance of ceramics; among them, Al2O3 ceramics with added TiC are the most widely used. In order to improve the bonding strength between Al2O3 and TiC, a small amount of metal (Ni or Co) is added to improve the interface wettability between Al2O3 and TiC. The prepared tools are suitable for high-speed rough and fine machining of difficult-to-machine materials such as wear-resistant cast iron, hardened steel and high-strength steel. Compared with pure Al2O3 ceramics, the bending strength of Al2O3-TiC ceramics is higher than that of pure Al2O3 ceramics at both room temperature and high temperature.

[0004] Al2O3 and TiC react at high temperatures: The production of CO gas results in low density of the prepared Al2O3-TiC ceramic tool. The solution is to mix Y2O3 into Al2O3 and TiC to reduce the contact between Al2O3 and TiC, thereby inhibiting the occurrence of the reaction.

[0005] At present, Y2O3, Al2O3, TiC, etc. in the industrially produced Al2O3-TiC ceramic tools are directly ball-milled and mixed in the form of nanopowder or micron powder to obtain mixed powder. In particular, Y2O3 and a small amount of metal are directly added in the form of powder by ball-milling, which will result in uneven mixing. Pores will be generated in places where there is no Y2O3, and abnormal growth of TiC grains will occur in places where there is a small amount of metal content. The presence of these defects will reduce the performance of the ceramic tool, resulting in large fluctuations in the performance of the prepared ceramic tool products, and bring unpredictable risks to cutting. Summary of the invention

[0006] In order to solve the problems existing in the prior art, the main purpose of the present invention is to propose an alumina-based ceramic cutting tool and a preparation method thereof, which can obtain a Ni-Y2O3-Al2O3 composite powder uniformly coated with Ni and Y2O3. This composite powder can be directly ball-milled with TiC to prepare Al2O3-TiC ceramics with uniform organizational structure, high relative density, good hardness and fracture toughness.

[0007] To solve the above technical problems, according to one aspect of the present invention, the present invention provides the following technical solutions:

[0008] A method for preparing an alumina-based ceramic cutting tool comprises the following steps:

[0009] S1. Preparation of composite powder: ball milling alumina powder and a nitrate solution obtained by dissolving yttrium nitrate hexahydrate and nickel nitrate hexahydrate in anhydrous ethanol, followed by calcination to decompose the nitrate to obtain NiO-Y2O3-Al2O3 composite powder uniformly coated with NiO and Y2O3;

[0010] S2, reduction treatment: placing the NiO-Y2O3-Al2O3 composite powder in a tube furnace, introducing hydrogen to reduce NiO to metallic Ni, and obtaining a Ni-Y2O3-Al2O3 composite powder;

[0011] S3, preparing ceramic composite powder: compounding Ni-Y2O3-Al2O3 composite powder and TiC powder, and obtaining Al2O3-TiC ceramic composite powder after ball milling and drying;

[0012] S4. Preparation of ceramic cutting tools: placing Al2O3-TiC ceramic composite powder in a graphite mold for hot pressing and sintering to obtain Al2O3-TiC ceramic samples, and then processing them into ceramic cutting tools of desired shapes through laser cutting, grinding and sharpening.

[0013] As a preferred embodiment of the method for preparing an alumina-based ceramic cutting tool described in the present invention, in the step S1, the purity of yttrium nitrate hexahydrate and nickel nitrate hexahydrate are both greater than 99%.

[0014] As a preferred embodiment of the method for preparing an alumina-based ceramic cutting tool according to the present invention, in the step S1, the time for ball-milling the nitrate solution and the alumina powder is 4 to 20 hours.

[0015] As a preferred embodiment of the method for preparing an alumina-based ceramic cutting tool described in the present invention, in which: in the step S1, the calcination is divided into two stages, the calcination temperature of the first stage is 400~600°C, and the calcination time is 2~5h, and the calcination temperature of the second stage is 600~900°C, and the calcination time is 3~5h.

[0016] As a preferred embodiment of the method for preparing an alumina-based ceramic cutting tool described in the present invention, wherein: in the step S1, in the NiO-Y2O3-Al2O3 composite powder, the mass ratio of Y2O3 to Al2O3 is 1:(48~123), and the mass ratio of NiO to Al2O3 is 1:(20~146).

[0017] As a preferred embodiment of the method for preparing an alumina-based ceramic cutting tool described in the present invention, in step S2, the reduction temperature is 600-750° C. and the time is 4-6 hours.

[0018] As a preferred embodiment of the method for preparing an alumina-based ceramic cutting tool described in the present invention, in which: in the step S2, the NiO-Y2O3-Al2O3 composite powder is sieved before reduction, and the mesh number of the sieve is 100-300 meshes.

[0019] As a preferred embodiment of the method for preparing an alumina-based ceramic cutting tool described in the present invention, in which: in the step S3, the particle size of the TiC powder is 0.3~1.0μm, and the amount of TiC powder added is 20~40wt% of the total mass of the TiC powder and the Ni-Y2O3-Al2O3 composite powder.

[0020] As a preferred embodiment of the method for preparing an alumina-based ceramic cutting tool described in the present invention, in step S4, the hot pressing sintering temperature is 1650-1750° C., and the pressing pressure is 20-40 MPa.

[0021] To solve the above technical problem, according to another aspect of the present invention, the present invention provides the following technical solution:

[0022] An alumina-based ceramic cutting tool is prepared by adopting the above-mentioned method for preparing the alumina-based ceramic cutting tool.

[0023] As a preferred embodiment of the alumina-based ceramic cutting tool described in the present invention, the alumina-based ceramic cutting tool has a uniform microstructure, a relative density ≥ 98.5%, a hardness HV3 ≥ 2050, a bending strength ≥ 800 MPa, and a fracture toughness Kic ≥ 6.0 MPa·m 1 / 2 .

[0024] The beneficial effects of the present invention are as follows:

[0025] The invention provides an alumina-based ceramic cutting tool and a preparation method thereof. A salt solution of nickel nitrate and yttrium nitrate is ball-milled and mixed with Al2O3, so that yttrium ions and nickel ions can be well coated on the surface of Al2O3. Then, a Ni-Y2O3-Al2O3 composite powder uniformly coated with metal Ni and Y2O3 can be prepared by decomposing the salt solution mixture and reducing the decomposition product with H2. The composite powder can be directly ball-milled and mixed with TiC powder to prepare an alumina-based ceramic cutting tool with uniform organizational structure, high relative density, good hardness and fracture toughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0027] Figure 1 This is the SEM morphology of the Ni-Y2O3-Al2O3 composite powder prepared in Example 1.

[0028] Figure 2 This is the SEM morphology of the fracture of the Al2O3-TiC ceramics prepared in Example 3.

[0029] Figure 3 This is the SEM morphology of the polished surface of the Al2O3-TiC ceramic prepared in Example 3.

[0030] Figure 4 This is the SEM morphology of the polished surface of the Al2O3-TiC ceramic prepared in Example 1.

[0031] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0032] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments. 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.

[0033] The present invention provides an alumina-based ceramic cutting tool and a preparation method thereof. The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0034] The specific preparation parameters of the alumina-based ceramic cutting tools of Examples 1-6 are shown in Table 1 below:

[0035] Table 1 Preparation parameters of alumina-based ceramic cutting tools of Examples 1-6

[0036]

[0037] Example 1-6 According to the process parameters in Table 1, weighed Al2O3 powder was poured into a ball mill, and then the salt solution obtained by adding the weighed yttrium nitrate and nickel nitrate to anhydrous ethanol was poured into the ball mill to mix with the Al2O3 powder. The mixture of the Al2O3 powder and the salt solution after ball milling was directly placed in a muffle furnace for heating and calcining to completely decompose the nitrate, so that the decomposed nickel oxide and yttrium oxide uniformly coated the Al2O3 powder. The uniformly coated powder is placed in a tubular furnace and hydrogen is passed through to completely reduce the nickel oxide coated on the surface of the Al2O3 powder to metallic nickel, so as to form a Ni-Y2O3-Al2O3 composite powder whose surface is uniformly coated with metallic nickel and yttrium oxide; the composite powder is added into a ball mill together with weighed TiC powder, and anhydrous ethanol is added for ball milling and mixing to prepare an Al2O3-TiC ceramic composite powder; the Al2O3-TiC ceramic composite powder is placed in a graphite mold and hot-pressed and sintered to prepare an Al2O3-TiC ceramic sample; the ceramic sample is laser cut, and then ground and sharpened to obtain a ceramic cutting tool of a desired shape.

[0038] The specific preparation parameter conditions of the alumina-based ceramic cutting tools of Comparative Examples 1-4 are shown in Table 2 below:

[0039] Table 2 Preparation parameters of alumina-based ceramic cutting tools of Comparative Examples 1-4

[0040]

[0041] The difference between Comparative Example 1 and Example 1 is that the ratios of Y2O3 and NiO to Al2O3 are 1:155 and 1:13 respectively, and the mass fraction of TiC is 16wt%;

[0042] The difference between Comparative Example 2 and Example 2 is that the particle size of the TiC powder used is 1.5 μm;

[0043] The difference between Comparative Example 3 and Example 3 is that: the reduction temperature of H2 is 850°C;

[0044] The difference between Comparative Example 4 and Example 4 is that the hot pressing sintering temperature is 1600°C.

[0045] The flexural strength, hardness and density of the alumina-based ceramics prepared in each embodiment and comparative example were tested. The results are shown in Table 3. It can be seen that the flexural strength of the alumina-based ceramics prepared in the present invention is ≥800 MPa, the relative density is ≥99%, the hardness is ≥2050, and the fracture toughness Kic is ≥6.0 MPa·m 1 / 2The tests of flexural strength, hardness, density and fracture toughness were carried out in accordance with JB / T 12613-2016 Ceramic Tool Material Performance Test Method. The specimen strip size for flexural strength was 4mm×3mm×46mm, the span was 30mm, and the loading rate was 0.5mm / min; the density was tested by the Archimedes drainage method, and the hardness and fracture toughness were tested by the indentation method, with a loading pressure of 3kg.

[0046] Table 3 Properties of alumina-based ceramics prepared in various embodiments and comparative examples

[0047]

[0048] The ceramic samples of Example 1, Example 4, Comparative Example 1 and Comparative Example 4 were prepared into CNGA120408T01025 ceramic turning inserts, and the prepared ceramic inserts were subjected to a turning test. The test material was alloy steel 35CrMo (HRC55), the turning method was dry continuous cutting, and the cutting parameters were: cutting speed Vc was 200m / min, feed was 0.2mm / rev, cutting depth was 0.7mm, and the tool failure was judged when the rear tool face wear VB reached 0.2mm; the cutting life results of the tool are shown in Table 4, and it can be seen that the cutting life of the alumina-based ceramic cutting tool prepared by the method of the present invention is significantly longer than that of the comparative example.

[0049] Table 4 Cutting life of ceramic tools

[0050]

[0051] The present invention adopts a salt solution of nickel nitrate and yttrium nitrate to mix with Al2O3 by ball milling, so that yttrium ions and nickel ions can be well coated on the surface of Al2O3, and then Ni-Y2O3-Al2O3 composite powder uniformly coated with metal Ni and Y2O3 can be prepared by decomposing the salt solution mixture and reducing the decomposition product with H2. The composite powder can be directly mixed with TiC powder by ball milling to prepare an alumina-based ceramic cutting tool with uniform organizational structure, high relative density, good hardness and fracture toughness.

[0052] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for preparing an alumina-based ceramic cutting tool, characterized in that: The following steps are involved: S1. Preparation of composite powder: ball milling alumina powder and a nitrate solution obtained by dissolving yttrium nitrate hexahydrate and nickel nitrate hexahydrate in anhydrous ethanol, followed by calcination to decompose the nitrate to obtain NiO-Y2O3-Al2O3 composite powder uniformly coated with NiO and Y2O3; in the NiO-Y2O3-Al2O3 composite powder, the mass ratio of Y2O3 to Al2O3 is 1:(48-123), and the mass ratio of NiO to Al2O3 is 1:(20-146); S2, reduction treatment: placing the NiO-Y2O3-Al2O3 composite powder in a tube furnace, introducing hydrogen to reduce NiO to metallic Ni, and obtaining a Ni-Y2O3-Al2O3 composite powder; S3, preparing ceramic composite powder: compounding Ni-Y2O3-Al2O3 composite powder and TiC powder, and obtaining Al2O3-TiC ceramic composite powder after ball milling and drying; the particle size of TiC powder is 0.3-1.0 μm, and the amount of TiC powder added is 20-40wt% of the total mass of TiC powder and Ni-Y2O3-Al2O3 composite powder; S4. Preparation of ceramic cutting tools: Place Al2O3-TiC ceramic composite powder in a graphite mold for hot pressing and sintering at a hot pressing temperature of 1650~1750℃ to obtain Al2O3-TiC ceramic samples, and then process them into ceramic cutting tools of the desired shape through laser cutting, grinding and sharpening, with a relative density of ≥98.5%, hardness HV3 ≥2050, bending strength ≥800MPa, fracture toughness K IC ≥6.0MPa·m 1 / 2 .

2. The method for preparing an alumina-based ceramic cutting tool according to claim 1, characterized in that: In step S1, the purity of yttrium nitrate hexahydrate and nickel nitrate hexahydrate are both greater than 99%.

3. The method for preparing an alumina-based ceramic cutting tool according to claim 1, characterized in that: In step S1, the time for ball milling the nitrate solution and the alumina powder is 4 to 20 hours.

4. The method for preparing an alumina-based ceramic cutting tool according to claim 1, characterized in that: In step S1, the calcination is divided into two stages. The calcination temperature of the first stage is 400-600° C. and the calcination time is 2-5 hours. The calcination temperature of the second stage is 600-900° C. and the calcination time is 3-5 hours.

5. The method for preparing an alumina-based ceramic cutting tool according to claim 1, characterized in that: In step S2, the reduction temperature is 600-750° C. and the time is 4-6 hours.

6. The method for preparing an alumina-based ceramic cutting tool according to claim 1, characterized in that: In the step S2, the NiO-Y2O3-Al2O3 composite powder is sieved before reduction, and the mesh number of the sieve is 100-300 meshes.

7. The method for preparing an alumina-based ceramic cutting tool according to claim 1, characterized in that: In step S4, the pressurization pressure is 20-40 MPa.

8. An alumina-based ceramic cutting tool, characterized in that: The alumina-based ceramic cutting tool is prepared by the preparation method of any one of claims 1 to 7, and the alumina-based ceramic cutting tool has a uniform microstructure.

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