KR0131834B1 - Method for manufacturing al2o3-ticxni-x system sintered body for cutting tool - Google Patents

Abstract

ATCN based cutting tool sintered body having an improved mechanical strength was manufactured by forming TiO2 coating layer on the surfaces of raw material particles. A mixture of 78-18 wt.% of Al2O3, 20-80 wt.% of TiCN, and 0.1-2 wt.% of Y2O3 was sprayed with a mixed gas of TiCl4, H2, H2O at 150-250 deg.C for 0.2-2 hours, wherein the coating layer was in the range of 0.1-0.5um thick and the weight of the layer was up to 5% of the total weight. The coated mixture powder was molded by press, and sintered at 1,500-1,800 deg.C for 0.5-1 hour in the presence of argon gas to give the Al2O3-TiCxN1-x(x is more than 0.2 and less than 0.8) based cutting tool sintered body.

Description

Manufacturing method of Al2O3-TiCxN1-X cutting tool sintered body

The present invention relates to a method for producing a sintered body of Al ₂ O ₃ -TiCxN _1-X (hereinafter referred to as ATCN) cutting tool, and more particularly, Al ₂ O ₃ and TiCxN _1-X system, which are the main raw materials produced during the production of the sintered body. A method for producing an ATCN-based cutting tool sintered body having a TiO ₂ coating layer formed on the surface of a raw material powder to reduce the reaction between the sintered catalysts and improving mechanical strength such as oxidation resistance, abrasion resistance, thermal shock resistance and thermal conductivity. will be.

In general, ceramic cutting tools have better wear resistance than carbide cutting tools, but are less reliable as tools due to their weakness, but their market share is gradually increasing due to the automation trend of machines worldwide.

As a result, the conventional Al ₂ O ₃ -TiC-based cutting tools (hereinafter referred to as AT-based cutting tools) have been gradually developed to improve toughness and reliability. However, AT-based cutting tool sintered bodies are manufactured due to poor sintering properties. There are problems such as the increase in unit cost, the complexity of the manufacturing process due to thermal compression, the cost increase and the mass production.

The problem as described above is due to the poor sinterability due to the generation of gas such as O ₂ and CO by the interfacial reaction of Al ₂ O ₃ and TiC, the main component of the sintered body during the sintering process, thereby forming residual pores in the final sintered body.

Commonly known AT-based interfacial reactions are as follows;

Al ₂ O ₃ (s) + 2C (s) → Al ₂ O (g) + 2CO (g)

Al ₂ O ₃ (s) + TiC (s) → Al ₂ O (g) + TiO (s) + CO (g)

Al ₂ O ₃ (s) +2/3 TiC (s) → Al ₂ O (g) +2/3 TiO ₂ (s) + 2 / 3CO (g)

Al ₂ O ₃ (s) + C (s) → Al ₂ O ₂ (g) + CO (g)

Al ₂ O ₃ (s) + C (S) → 2Al (g) + CO (g)

In the above, s is a solid phase and g is a gas phase.

Another problem with the AT system is the high fragility of TiC and the strong chemical reactivity or oxidative power of the workpieces experienced in actual work sites.

In order to overcome the above disadvantages, in general, a hot-pressing method, a hot isostatic pressing after sintering (HIP), a method of rapidly increasing the temperature above 1800 ℃ or a method of adding a sintering aid such as Y ₂ O ₃ Etc. are used.

In recent years, TiCN has higher oxidation resistance than TiC, and the thermal conductivity due to the nitriding of TiC increases, thereby reducing the heat accumulation transmitted to the cutting tool during steel cutting, thereby improving the wear resistance of the cutting tool by suppressing softening. In order to manufacture AT-based cutting tools (particularly cement cutting tools), the use of TiCN rather than TiC is emerging as a method for manufacturing a new cutting tool.

However, when replacing the TiC as TiCN in the Al ₂ O interfacial reactivity of the ₃ and TiCN is there is expected shall be compounded than in the case of TiC, which is a NO or NO ₂ gas to the reaction similar to the interfacial reaction of TiC and Al ₂ O ₃ Because it can be formed.

The reaction formula for forming NO ₂ gas of NO by the interfacial reaction between Al ₂ O ₃ and TiCN is as follows.

Al ₂ O ₃ + TiCN → Al-Ti-O-C + NO (or NO ₂ ) (g)

In the above, g is a gas phase.

Accordingly, the present inventors solved the ovarian formation due to the interfacial reactivity of the Al ₂ O ₃ -TiCxN _1-X (0.2x0.8) -based main components, such as oxidation resistance, abrasion resistance, thermal shock resistance and thermal conductivity of the sintered ATCN-based cutting tool The result of intensive studies to improve the mechanical strength has led to the present invention.

An object of the present invention, Al ₂ O _3, TiCN, and Y ₂ O ₃ in the starting material mixture or the most simple and evenly coat the TiO ₂ layer to that of each of the powders are not mixed by by the coating layer during sintering Al ₂ O _3, TiCN It is to provide a method for producing an ATCN-based cutting tool with a significantly reduced interfacial reaction.

It is also an object of the present invention to provide an ATCN-based cutting tool having excellent mechanical strength properties such as oxidation resistance, abrasion resistance, thermal shock resistance and thermal conductivity.

Hereinafter, the present invention will be described in detail.

In the present invention, Al ₂ O ₃ , TiCN Y ₂ O ₃ mixed finely ground powder or each unpulverized finely ground powder is placed in a reactor, and mixed gas of TiCl ₄ and H ₂ and H ₂ O at 150 to 250 ° C. The present invention relates to a method for producing a sintered ATCN cutting tool, characterized in that the mixed gas of N ₂ is gas sprayed onto the above-described raw powder at about the same time to form a TiO ₂ coating layer, and then molded and sintered.

Hereinafter, the present invention will be described in more detail.

According to the present invention, in order to manufacture the sintered ATCN seasonal cutting tool, first, 78 to 18% by weight of Al ₂ O ₃ , 20 to 80% by weight of TiCN and 0.1 to 2% by weight of Y ₂ O ₃ are mixed and ground.

In the composition ratio of the raw material mixture, when using 78 wt% or more of Al ₂ O ₃ , that is, when using 20 wt% or more of TiCN, there is a problem that the toughness and hardness of the sintered body is lowered.

In addition, when using Al ₂ O ₃ of less than 18% by weight, that is, when using less than 80% by weight of TiCN, there is a problem that the sintering temperature rises sharply.

After mixing each material, the mixed raw materials were dried and funneled, and then placed in a reactor, and the mixed gas of TiCl ₄ and H _{2 and} the mixed gas of H ₂ O and N ₂ were simultaneously pulverized as a carrier gas. The coating powder is prepared by gas spraying the mixed powder flowing for 0.2 to 2 hours to form a TiO ₂ coating layer.

In preparing the coating layer, the reaction temperature is preferably 150 to 250 ° C. and the reaction time is 0.2 to 2 hours. If the temperature is 150 ° C. or less or 0.2 hour or less, the formation of the TiO ₂ coating layer is insufficient, and the temperature is 250 ° C. or more or 2 hours. In the case of the above problem, excessive TiO ₂ coating layer is formed.

The carrier gas used for preparing the TiO ₂ coating layer, that is, the mixed gas of TiCl ₄ and H _{2 and} the mixed gas of H ₂ O and N ₂ , is preferably used heated to about 170 ° C.

The mixed powder coated by the above method is molded into a shape using a press, and then sintered at an temperature of 1500 to 1800 ° C. for 0.5 to 1 hour under an argon atmosphere to prepare an ATCN-based cutting tool sintered body.

In the sintering condition, the strength of the sintered compact is reduced when the sintering temperature is less than or equal to 1500 ° C or when the sintering time is 0.5 hours or less, and when the sintering temperature is 1800 ° C or more or the sintering time is more than 1 hour, the strength of the sintered compact is The problem is that it is degraded.

The TiO ₂ coating layer coated in the above process is preferably 5% by weight or less of the total weight, the thickness of the coating layer is slightly different depending on the composition ratio of the raw material, but 0.1 to 0.5 m is preferred.

If the thickness of the coating layer is 0.1 m or less, the formation of the TiO ₂ coating layer becomes insufficient, and when the thickness of the coating layer is 0.5 m or more, the TiO ₂ coating layer is excessively generated, making it difficult to form the sintered body.

In another embodiment according to the present invention, a method of manufacturing the ATCN-based cutting tool sintered body is as follows.

First, 78 to 18% by weight of Al ₂ O ₃ , 20 to 80% by weight of TiCN and 0.1 to 2% by weight of Y ₂ O ₃ are respectively pulverized, and the pulverized raw powder is dried and funneled, respectively.

Then, each of the powders described above was put into a reactor, and the mixed gas of TiCl ₄ and H _{2 and} the mixed gas of H ₂ O and N ₂ which were heated from 150 to 250 ° C. to about 170 ° C. were flowed at about the same time. Gas sprayed on a powder of 0.2 to 2 hours to form a TiO ₂ coating layer on the raw material powder to prepare a coating powder.

Then, after mixing each raw material powder in which the coating layer was formed with a bowl mill, the mixed coating powder is shape | molded by the press at constant shape, and it sinters at 1500-1800 degreeC under argon atmosphere.

The formation reaction of the TiO ₂ coating layer in the above process is as follows.

The TiO ₂ coating layer formed in the above scheme prevents gas generation generated by the reaction between Al ₂ O ₃ and TiCN two materials during sintering of the ATCN-based molded body.

In addition, the TiO ₂ layer, which is very uniformly coated between particles at 0.1 to 0.5 μm, forms a very uniform interface even in the sintered body, thereby inhibiting sintering promoting effect, abnormal grain growth of crystal grains, oxidation resistance and heat resistance of the cutting tool. It can contribute to the manufacture of ATCN-based cutting tools excellent in mechanical strength characteristics such as impact resistance, wear resistance and thermal conductivity.

The role of TiO ₂ for improving the sinterability and strength of the sintered body is well illustrated in Korean Patent Nos. 058864, 058865, and Japanese Patent Publication No. 53-14568.

Further, the coupling between the method of the present invention, Japanese Patent Publication No. 51-569 cows and cow mixing effect greater than the independent addition of a TiO ₂ powder in the method disclosed No. 64-1430 or the like, and Al ₂ O ₃ and TiCN-based Increasing the strength improves the wear resistance and the life of the cutting tool.

Hereinafter, the present invention will be described in more detail with reference to Examples.

[Examples 1 to 3]

The raw material powders of Al ₂ O ₃ , TiCN and Y ₂ O ₃ in the amounts shown in Table 1 were mixed and ground in a WC jar (Jar) using alcohol as a mixed solvent.

After the mixed slurry was sufficiently dried, the mixture was mixed in a funnel, and the mixed gas of TiCl ₄ and H ₂ (TiCl ₄ : 0.01 to 0.2% by volume) and the mixed gas of H ₂ O and N ₂ were simultaneously introduced into the coating reactor. Sprayed.

At this time, the temperature of the reactor was 150 ° C., and the reaction time was 0.5 hour.

The weight of the TiO ₂ formed after the reaction was 5% by weight or less based on the total weight of the mixed powder.

The optimum conditions for forming the TiO ₂ coating layer depend on the gas flow rate and reaction time, but showed the most optimal sintered body properties when coated to increase the weight by about 5% by weight based on the total powder weight.

At this time, the flow rate of the mixed gas was 0.1 to 0.3 l / min.

The powder coated as described above was formed through a molding process (uniaxial pressure drying molding), and then sintered under an argon atmosphere at about 1500 to 1800 ° C. for 0.5 to 1 hour.

In general, the ceramic cutting tool has a great influence on the cutting ability by changing the toughness during cutting depending on the particle size of the sintered body.

In other words, if the sintered body particles are large due to the high sintering temperature, the cutting life is lowered. Therefore, in order to prevent this, after obtaining a certain sintered density in an atomized state (possible low temperature sintering) where the particle size of the sintered body is possible (94 to 96% true density) HIP (Hot Isostatic Prerv) was performed and densified.

HIP was carried out in an argon atmosphere at a temperature of 1450 to 1650 ° C. for about 0.5 to 1 hour.

The phase of the sintered body was analyzed by XRD and XRF, and the microstructure was observed by SEM and EDAX.

The mechanical properties of the prepared sintered body were estimated by Hicker and VIC before the actual cutting test (Vicker's Indenter), the amount of cutting wear was measured and the results are shown in Table 1.

[Comparative Example I-1 to I-2]

The AT-based cutting tool sintered body was prepared by the method described in Korean Patent No. 058865 using Al ₂ O ₃ , TiC and Y ₂ O ₃ raw powders in the amounts described in Table 1 below.

The mechanical properties of the prepared sintered compact were measured according to the method of Example 1, and the results are shown in Table 1.

Comparative Example II -1 to II -2

ATCN-based cutting tool sintered body was prepared in the same manner as in Example 1 except that the TiO ₂ coating layer was not formed using the Al ₂ O ₃ , TiCN and Y ₂ O ₃ raw powder in the amounts shown in Table 1 below. It was.

The mechanical properties of the prepared sintered body were measured according to the method of Example 1, and the results are shown in Table 1.

ATCN-based cutting tool sintered body produced by the present invention has improved cutting performance of about 3 to 4 times compared to AT-based, and 1.5 to 2 times compared to general ATCN-based cutting tools without a coating layer. It also showed surprising breakdown reliability.

This is presumably because the raw material mixture made of the coated powder according to the present invention is easy to densify in sintering the sintered compact and forms a very uniform microstructure having a particle diameter of about 0.1 to 1 탆.

Claims (2)

Mix the mixed or pulverized powder of Al ₂ O ₃ , TiCN and Y ₂ O ₃ , or each of the unpulverized pulverized powder, into the reactor, and mix gas of TiCl ₄ and H ₂ and H ₂ O and N at 150-250 ℃ Al ₂ O ₃ -TiCxN _1-X (0.2x0.8) -based cutting tool, characterized in that the mixed gas of ₂ is gas-sprayed on the above-mentioned raw powder at about the same time to form a TiO ₂ coating layer, and then molded and sintered. Method for producing sintered body. The method for manufacturing a sintered body of Al ₂ O ₃ -TiCxN _1-X (0.2x0.8) -based cutting tool according to claim 1, wherein the TiO ₂ coating layer is 5% by weight or less of the total weight of the mixed powder.