JPH0516031A - Manufacture of sheathed ceramic tool of high toughess and durability - Google Patents

Abstract

PURPOSE:To improve the durability of a sheathed ceramic tool by forming a sheath layer of Tic, TiN, TicN, Al2O3 or AlON, or the combination thereof on the surface of a base material comprising Al2O3-ZrO2 ceramic sinterd body having the predetermined composition of ZrO2 and Al2O3, using a CVD method. CONSTITUTION:A base material is formed with an Al2O3-ZrO2 ceramic sintered body containing 1 to 5wt% of ZrO2, and Al2O3 as a remnant. In addition, a sheath layer comprising one or the combination of Tic, TiN, TicN, Al2O3 and AlON is formed on the surface of the base material via a CVD method. Also, the thickness of the sheath layer is set at a value between 0.3mum and 15mum. In this case, Tic, TiN and TicN may be used to form an inner layer and AlON to form an intermediate layer, while Al2O3 being used to form an outer layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high toughness and high durability ceramic tool based on an Al ₂ O ₃ --ZrO ₂ system ceramic sintered body.

[0002]

_2. Description of the Related Art Conventional Al ₂ O ₃ and Al ₂ O ₃ --Ti
C-based ceramic tools have the advantage of high hardness at high temperatures, but on the other hand, they are not necessarily good in strength or toughness, so they are not suitable for rough machining,
In addition, in the situation where the recent shift to NC in machine tools is progressing,
There is a drawback that the reliability as a tool is poor.

On the other hand, a ZrO ₂ type ceramic tool is disclosed in Japanese Patent Application Laid-Open No. 55-140762.
ZrO ₂ -based ceramic as the base material has a bending strength of 10
As it shows 0 kg / mm ² or more and toughness (Kic) 30 kg / mm ^3/2 or more, it has excellent characteristics comparable to cemented carbide, and has high strength and high toughness ZrO ₂ based ceramics. Is CaO, MgO, ZrO ₂ as the main component,
It is obtained by adding an oxide such as Y ₂ O _{3 to} partially stabilize a high temperature stable phase such as a tetragonal crystal or a cubic crystal at high temperature even at around room temperature.

Further, JP-A-52-86413 and JP-A-54-60 which disclose Al ₂ O ₃ -ZrO ₂ -based ceramics.
From 308 and JP-A-54-61215, it is known that by dispersing ZrO ₂ in an Al ₂ O ₃ matrix, considerably high toughness is exhibited.

[0005]

However, when such conventional ZrO ₂ -based ceramics and Al ₂ O ₃ -ZrO ₂ -based ceramics are used as cutting tool materials, Al ₂
Since it is superior in strength and toughness to O ₃ -based ceramics and Al ₂ O ₃ -TiC-based ceramics, it is suitable for rough machining, but on the other hand, for example, ductile cast iron and steel materials that are tough and difficult to cut are used. When the material to be cut is used, both flank wear and crater wear become remarkable. For this reason, conventional tools made of ZrO ₂ -based ceramics or Al ₂ O ₃ —ZrO ₂ -based ceramics are not good in wear resistance and cannot exhibit sufficient functions as cutting tools. Furthermore, in order to cut these difficult-to-cut materials at high speed, high impact resistance is essential for their durability.

The present invention has as its basic purpose to solve the problems of the conventional method, and has a sufficiently high strength and high toughness, and has a high durability especially for difficult-to-cut materials. It is an object to provide a ceramic tool.

[0007]

Therefore, the method of manufacturing a ceramic tool of the present invention provides a base material having sufficient strength and toughness with high hardness and adhesive force without deteriorating the original characteristics of the base material. A coating layer is provided. That is, according to the first aspect of the present invention, the present invention provides Al ₂ O _3- as a base material.
By forming the ZrO ₂ -based ceramic and the coating layer formed on the surface of the ZrO ₂ -based ceramic with at least one ceramic of TiC, TiN, TiCN, Al ₂ O ₃ and AlON by the CVD method, it is possible to obtain high toughness and impact resistance. Provide a highly durable ceramic tool.

In a second aspect of the present invention, the above object is based on an Al ₂ O ₃ -ZrO ₂ system ceramic sintered body having a composition of 1 to 50 wt% ZrO ₂ and the balance substantially Al ₂ O _3. (B) a step of forming an inner layer made of TiC, TiN or TiCN or a combination thereof on the surface of the material by a CVD method, (b) a step of forming an intermediate layer made of AlON on the surface of the inner layer by a CVD method, and ( C) A step of forming an outer layer made of Al ₂ O _{3 on} the surface of the intermediate layer by a CVD method, and a method for producing a high toughness and high durability coated ceramic tool.

In a third aspect of the present invention, the above object is based on an Al ₂ O ₃ -ZrO ₂ based ceramic sintered body having a composition of 1 to 50 wt% ZrO ₂ and the balance substantially Al ₂ O _3. And (b) forming an AlON inner layer on the surface of the material by a CVD method, and (b) forming an Al ₂ O ₃ layer on the surface of the inner layer by a CVD method. This is accomplished by a method of making a high toughness, high durability coated ceramic tool.

[0010] The composition of Al ₂ O ₃ -ZrO ₂ ceramic sintered body as a _substrate, ZrO 2 _1~50wt%, the balance substantially of Al ₂ O _3, preferably ZrO ₂ 1 to 30
wt% and the balance substantially Al ₂ O ₃ is preferable. 1 w of ZrO ₂
This is because when the content is at least t%, the strength of the base material, particularly the toughness, is significantly improved. Also, ZrO ₂ is 50 wt%
When it is set to the following (more preferably 30 wt% or less), the coating layer can be formed to a predetermined thickness at a high temperature without causing deterioration of the characteristics of the base material (especially necessary in the CVD method).

Maintaining a conventional ZrO ₂ sintered body at a high temperature near 1000 ° C. causes a phase transition accompanied by a rapid volume change.

[Equation 1] It has been considered that this causes a rapid deterioration of the strength of the base material. However, according to the invention, ZrO ₂ 50w
By setting the content to t% or less, it is possible to form a film at high temperature without causing deterioration of the base material.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Of these, ZrO ₂ preferably contains a stabilizer of a rare earth oxide such as CaO, MgO or Y ₂ O ₃ , but it is not always necessary to contain it. When the stabilizer is included, CaO or MgO is added to ZrO _{2 in} total.
15 wt% or less, and Y ₂ O ₃ is preferably 9 wt% or less with respect to ZrO ₂ . ZrO ₂ in this case is
It is preferable to have a partially stabilized structure in which tetragonal ZrO ₂ contains 5 wt% or more of the total amount. When ZrO ₂ is added to Al ₂ O ₃ in the production, partially stabilized ZrO ₂ may be added to Al ₂ O ₃ in advance, or monoclinic ZrO ₂ and a stabilizer may be added. Al ₂ O ₃ alone
May be added to.

On the other hand, when the stabilizer is not contained, it is preferable to use ZrO ₂ having an average particle size of 0.3 μm or less.
During the addition of ZrO ₂ to Al ₂ O ₃ , fine ZrO ₂ was
When dispersed in l ₂ O ₃ , ZrO ₂ remains tetragonal,
This is because an Al ₂ O ₃ —ZrO ₂ -based ceramic substrate having good toughness can be obtained.

The firing conditions for the Al ₂ O ₃ -ZrO ₂ -based ceramic substrate are as follows: in an oxidizing atmosphere, at a temperature of 1350 to 1650 ° C.
The processing time is a few minutes to a few hours. This is because if the temperature is lower than 1350 ° C., the sintering is not sufficiently performed, and if it exceeds 1650 ° C., the growth of crystal grains is remarkable and the strength and toughness of the base material are deteriorated. The base material thus constructed has a bending strength of about 60 kg / mm ² or more and a fracture toughness Kic of about 20 kg / mm ^3/2 or more.

Next, the ceramic as the coating material, according to the first aspect, consists of TiC, TiN, TiCN, Al ₂ O ₃ or AlON or a combination of these components (however, AlON is not preferred as the outer layer). The surface of the substrate may be coated with a single layer or multiple layers. The coating layer when the above components are combined to form a multilayer coating,
It is preferable to have two or more layers, for example, an inner layer, an intermediate layer, and an outer layer as shown in Table 1 (the intermediate layer is A
lON is preferred). From the second and third viewpoints, Al ₂ O ₃ is most suitable as the outer layer (because Al ₂ O ₃ has a high hardness of micro Vickers hardness of 2000 kg / mm ² or more). Inner layer of the Al ₂ O ₃ layer (to prevent peeling enhance the adhesion of the hard the Al ₂ O ₃ layer) AlON is optimal as (inner or intermediate layer).

The coating method in this case is generally PVD.
Method (Physical Vapor Deposition) and CVD method (Chemical
Vapor Deposition) and other physical or chemical deposition film forming methods are conceivable, but in view of the adhesion homogeneity of the coating material and the coating speed, the CVD method by the reaction shown below is used in the present invention.

TiCl ₄ + CH ₄ → TiC + 4HCl 2TiCl ₄ + N ₂ + 4H ₂ → 2TiN + 3HCl 2TiCl ₄ + 2CH ₄ + N ₂ → 2TiCN + 8HCl 2AlCl ₃ + 3CO ₂ + 3H ₂ → Al ₂ O ₃ + 3CO + 6HCl 2AlCl + 2CO ₂ + N ₂ + 3H ₂ → 2AlON + 2CO + 6HCl

Particularly for Al ₂ O ₃ and AlON layers, C
If it is not the VD method, it is difficult to form a practical film suitable for the purpose of the present invention (especially in terms of film forming speed and film stability). TiC,
The details of the coating method of TiN, TiCN, Al ₂ O ₃ , and AlON are known per se, so description thereof will be omitted, but generally a considerably high temperature is essential (800 ° C. or higher, preferably 950 to 950 ° C.).
1100 ° C).

There are many methods for forming various coating layers on the cemented carbide by the CVD method, starting from JP-B-42013 (TiC), and TiN and TiCN are JP-B-51-2498.
2, Al ₂ O ₃ is disclosed in JP-A-48-217, TiC, TiN /
The double coating of Al ₂ O ₃ and AlON / Al ₂ O ₃ is disclosed in JP-B-52-13201 and JP-A-54-29185, respectively, and a similar coating method can be used. However, these are not suitable for high-speed cutting because they all use cemented carbide as a base material. Regarding the conventional ceramic base material containing ZrO ₂ , it is necessary to maintain the high temperature of 1000 ° C. or higher after sintering (cooling) because the phase transformation accompanied by a large volume change in ZrO ₂ in this temperature range.

[Equation 2] Is caused and the strength is remarkably deteriorated, which is contraindicated. However, according to the present invention, it is surprising that, contrary to such an expectation, a dramatically improved property is achieved.

The thickness of the coating layer is 0.3 to 15 μm.
This is because if it is less than 0.3 μm, the function as a coating material is weakened, and if it exceeds 15 μm, the grain growth is apt to be easily peeled off during coating. When coating with Al ₂ O ₃ , the Al ₂ O ₃ layer thickness is preferably about 0.3 to 5 μm.

The ceramic tool constructed in this manner has high strength and high toughness sufficient to withstand repeated shocking and high-speed cutting of a tough-cutting material, and exhibits excellent characteristics in terms of wear resistance. . As a result, a highly reliable cutting tool that can be used in a highly automated cutting machine can be manufactured. This will be described based on the embodiments described below.

[0022]

EXAMPLES The raw materials used for the base material were Al ₂ O ₃ having a purity (wt%) of 99.9%, an average particle size of 0.6 μm, and monoclinic ZrO ₂ having a purity of 99% or more and an average particle size. 0.2μ
m, CaCO ₃ raw material CaO purity 98%, Mg
O has a purity of 97% or more and Y ₂ O ₃ has a purity of 9% or more.
It was 9.9% or more. Each sample of the base material has the composition as shown in Table 2, and after wet mixing the predetermined raw materials, drying and adding a binder, and granulating, the pressure is 1.5 kg / cm ²
Was press-molded. This green compact has its binder removed by calcination and then placed in an electric furnace at 1400 to 1650 ° C.
It was baked for 1 hour. This fired body has a size of 4 × 8 × 25m
polished to m.

The characteristics of each sample thus prepared are
As shown in the table. As is clear from Table 2, each sample has considerably higher transverse rupture strength and toughness than ordinary Al ₂ O ₃ transverse rupture strength of 50 kg / mm ² or less and toughness (Kic) 10 kg / mm ^3/2 or less. Is shown.

The measuring method of each characteristic of the sample is as follows. (1) Flexural strength is measured according to JIS B4104,
The average value of 5 is shown. (2) Fracture toughness is 0.5 mm in depth according to ASTM Special Technical Publication No.410 for a specimen with a width of 4 mm, a thickness of 5 mm and a length of 25 mm.
mm, width 0.15 mm notch, span 20 mm
Was measured by the three-point bending notch method. The measured value is an average value of 5 lines each. (3) As a crystal system, Geiger flex RAD-γA type manufactured by Rigaku Denki was used, and the crystal system was determined by X-ray diffraction. First, a sample mirror-polished with a 15 μm diamond paste was measured by X-ray diffraction to find that monoclinic ZrO ₂

[Equation 3] The amount of monoclinic ZrO ₂ is determined from the integrated intensity Im of the (111) face of the tetragonal ZrO ₂ and the ratio It + Ie of the integrated intensities of the (111) face of the cubic ZrO ₂ and the (111) face of the cubic ZrO _2. did. Then, the sintered body was pulverized to a total of 325 mesh, subjected to X-ray diffraction under the same conditions, and again monoclinic ZrO ₂ and cubic ZrO ₂
The integrated intensities I'm and I'e of At this time, the residual tetragonal ZrO ₂ in the sintered body is considered to be transformed into monoclinic ZrO ₂ by mechanical stress due to pulverization, so that I'e / (I'm + I'e) is converted into cubic ZrO 2. _The amount of ₂ was determined and then the amount of tetragonal ZrO ₂ was also determined.

Next, each of these samples was treated with SNGN432T.
Processed in the shape of N (throw away chip shape display method according to JIS008B), and C on the surface of this molded body (base material).
A predetermined coating layer was formed by the VD method. Specifically, H ₂ gas was caused to flow as a carrier gas into the reaction vessel in which the base material was set, and a predetermined coating material was attached to the surface of the base material with the above-mentioned chemical reaction (see Table 3). . The internal pressure of the reaction vessel is 100 when coating TiC, Al ₂ O ₃ and AlON.
mb, 300 mb for TiCN and 500 mb for TiN, and the temperature inside the reaction vessel was set to 1050 ° C. The coating rate was 1 μm / hr for TiC, TiN, and TiCN, and 0. 0 for Al ₂ O ₃ and AlON.
It was set to 5 μm / hr.

Using the ceramic tool (sample) thus obtained, milling cutting of ductile cast iron (FCD55) (test 1) and turning of chromium-molybdenum alloy steel (SCM44C) (test 2) were performed. The cutting conditions are shown in Table 4.

The results of this cutting test are as shown in Table 3. As can be seen from this table, in Test 1, sample Nos. 2 to 8 are sufficiently resistant to the impact of about 4000 to 5000 times. In contrast, reference sample Nos. 1 and 9 are 20
It is damaged by the impact of 00 to 2500 times. These No. 2
.About.8, 10 and No. 4a to 4g groups have extremely long lives (compared to 10 to 50 times or more) as compared with Comparative Examples 1 to 4, so Al ₂ O ₃ formed by forming a predetermined coating layer.
-ZrO ₂ based ceramic proves to be particularly effective in the milling of ductile iron with a predetermined thickness. Further, from Test 2 as well, it can be seen that the Al ₂ O ₃ —ZrO ₂ -based ceramic having the predetermined coating layer formed thereon has excellent flank wear resistance in turning steel. A
The effect of the ON layer is clear by comparing No. 4a and No. 4 with No. 4b and 4d, respectively.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

[Table 4]

[0032]

As described above, according to the present invention,
An Al ₂ O ₃ —ZrO ₂ -based ceramic containing Al ₂ O ₃ as a main component is used as a base material, and TiC, TiN, TiCN, Al ₂ O ₃ , A as a predetermined thin film is formed on the surface of the base material.
By forming the coating layer made of at least one ceramic of lON by the CVD method, it is possible to manufacture a ceramic tool that exhibits extremely high strength and toughness (impact resistance) without causing deterioration of the base material (No. 1). 1 viewpoint). As a result, there is an effect of exhibiting excellent wear resistance which cannot be obtained by the conventional ceramic tools. In particular, from the second and third viewpoints, it is possible to form high hardness Al ₂ O ₃ (outer layer) through AlON (the inner layer) by the CVD method without deteriorating the strength of the ZrO ₂ base material. This is beyond the expectations of those skilled in the art.

The ceramic tool produced according to the present invention is not only a tool for cutting and turning, but also a die for wire drawing and other tools for working metal, etc. which are required to have wear resistance, toughness and hardness. It can be applied.

Claims (8)

[Claims] 1. ZrO ₂ 1 to 50 wt%, the balance being substantially A
TiC, TiN, and TiC are formed on the surface of a substrate made of an Al ₂ O ₃ -ZrO ₂ -based ceramic sintered body having a composition of 1 ₂ O _3.
A method for producing a high toughness and high durability coated ceramic tool, which comprises forming a coating layer made of N, Al ₂ O ₃ or AlON or a combination thereof by a CVD method. 2. The manufacturing method according to claim 1, wherein the coating layer is formed to a thickness of 0.3 to 15 μm. 3. ZrO _{2 1 to} 50 wt%, the balance substantially A
a step of forming an inner layer of (a) TiC, TiN or TiCN or a combination thereof on the surface of a base material made of an Al ₂ O ₃ -ZrO ₂ based ceramic sintered body having a composition of l ₂ O ₃ by a CVD method. And (b) forming an intermediate layer of AlON on the surface of the inner layer by the CVD method, and (c) forming an outer layer of Al ₂ O _{3 on} the surface of the intermediate layer by the CVD method. A method for producing a ceramic tool having a high toughness and a high durability, which is characterized. 4. The method according to claim 3, wherein the coating layer composed of the inner layer, the intermediate layer, and the outer layer is formed to a thickness of 0.3 to 15 μm. 5. The method according to claim _{3, wherein} the outer layer of Al ₂ O ₃ is formed to have a thickness of 0.3 to 5 μm. 6. ZrO _{2 1 to} 50 wt%, the balance substantially A
(a) a step of forming an inner layer made of AlON by a CVD method on the surface of a base material made of an Al ₂ O ₃ -ZrO ₂ system ceramic sintered body having a composition of l ₂ O ₃ ; And a step of forming a layer composed of Al ₂ O ₃ by a CVD method, and a method for producing a high toughness and high durability coated ceramic tool. 7. A coating layer comprising an inner layer and an Al ₂ O ₃ layer,
The manufacturing method according to claim 6, wherein the thickness is 3 to 15 μm. 8. The manufacturing method according to claim 7, wherein the Al ₂ O ₃ layer is formed to a thickness of 0.3 to 5 μm.