JP3147511B2 - Alumina sintered body for tools - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered body for a tool having a surface portion having a so-called gradient composition structure in which the composition of the surface portion of an alumina sintered body is gradually changed, a method for producing the same, and a method for producing the same. More specifically, the present invention relates to a sintered body for a tool in which a film is formed on the surface of the sintered body, specifically, a cutting tool such as a turning tool, a milling tool, a drill, an end mill, a die, a punch, a slitter,
The present invention relates to an alumina sintered body for a tool, which is most suitable as a wear-resistant tool such as a center, a method for producing the same, and an alumina sintered body for a tool having a film formed on the surface of the sintered body.

[0002]

2. Description of the Related Art Conventionally, MgO, Y is contained in alumina as a main component.
High density alumina in which additives such as ₂ O ₃ , Cr ₂ O ₃ , NiO, TiO ₂ , ZrO ₂ or carbides, nitrides, carbonitrides, etc. of metals of the 4a, 5a, 6a group of the periodic table are uniformly distributed. Some sintered bodies have been practically used for tools. However, in these high-density alumina sintered bodies, the properties of the sintered bodies themselves only fluctuate according to the properties of the additives uniformly distributed, and in the end, the excellent wear resistance of alumina is maintained. There is a problem that no improvement in toughness and strength can be expected, and conversely, there is a trade-off tendency that the wear resistance for improving toughness, strength and thermal properties is reduced.

[0003] To solve this problem,
Many proposals have been made for modifying the surface of the alumina sintered body, and one of them is to apply a chemical vapor deposition (CVD) or physical vapor deposition (PVD) method to the surface of the alumina sintered body. There is a coated alumina sintered body with a coating formed.
There is a method in which the surface of the alumina sintered body is modified by a method other than the VD method or the PVD method.

[0004] Of these, representatives of the latter are disclosed in JP-A-60-103090 and JP-A-2-157149.
There is an official gazette.

[0005]

Among the prior arts in which the surface of an alumina sintered body has been modified, Japanese Patent Application Laid-Open No. Sho 60-103090.
Japanese Patent Application Laid-Open Publication No. H11-163873 discloses an alumina sintered body in which mullite and B ₂ O ₃ are added to the main component of α-Al ₂ O ₃ containing SiO ₂ and a mullite precipitation layer is formed on the surface of the sintered body during sintering. Is described.

Japanese Unexamined Patent Publication (Kokai) No. 2-157149 discloses a multi-component ceramic in which the ratio of each composition of a ceramic having a plurality of compositions is continuously changed.
It is described that in the upper portion of the Al ₂ O ₃ —SiO ₂ sintered body, Al ₂ O ₃ is small and the composition change in which SiO ₂ is increased continuously occurs.

The sintered bodies described in these two publications are:
Unlike films formed by CVD or PVD,
Although it is an excellent sintered body in which the peeling of the coating hardly occurs or distortion or the like due to the difference in thermal expansion between the surface and the inside is eased, the wear resistance is poor because the surface is soft, and in particular, There is a problem that it cannot be used in severe applications such as tools.

The present invention has solved the above-mentioned problems. Specifically, the present invention has been applied to a surface conditioning layer having a thickness of at least 0.05 mm from the surface of a sintered body containing alumina as a main component. By forming a compound and gradually decreasing the elements that form this compound toward the inside, the properties of the surface conditioning layer and the inside of the sintered body are maximized, and the wear resistance, toughness, strength and heat resistance And to provide a tool alumina sintered body that can be practically used as a tool, especially as a cutting tool.

[0009]

Means for Solving the Problems Although the conventional alumina-based sintered body improves certain characteristics of the sintered body by adjusting the composition components, on the other hand, the other necessary characteristics are considered. In the process of manufacturing the alumina-based sintered body, a compound that is easy to diffuse when sintering a powder compact, When a compound capable of imparting abrasion resistance, toughness, heat resistance and corrosion resistance is diffused with a concentration gradient in the surface layer of the binder, various properties are simultaneously improved without lowering certain properties. Based on the knowledge, the present invention has been completed.

That is, the alumina sintered body for a tool of the present invention has a surface conditioning layer having a thickness of at least 0.05 mm from the surface of a part or the entire surface of the sintered body containing alumina as a main component. Are formed on the surface-tempered layer, and elements 3a, 4a, 5a, and 6a of the periodic table, Fe,
An alumina sintered body containing a compound containing at least one of Ni, Co, and Si, wherein the surface conditioning layer comprises:
3a, 4a, 5 of the periodic table contained as the compound
At least one of the diffusion elements among the elements of Group a and 6a, Fe, Ni, Co, and Si gradually decreases from the surface of the surface-tempered layer toward the inside of the sintered body. 05
The ratio of the concentration (Cs) of the diffusion element present in the surface conditioning layer in the interior of the sintered body to the concentration (Ci) of the diffusion element in the sintered body excluding the surface conditioning layer is 1.5 or more. (C
s / Ci ≧ 1.5).

[0011] The sintered body containing alumina as a main component in the sintered body of the present invention means that the inside of the sintered body excluding the surface conditioning layer contains at least 50% by weight of granular, plate-like and / or fibrous α-alumina. and the balance _{MgO, Y 2 O 3, Cr} 2 O 3, HfO 2, Z
rO ₂ , NiO ₂ , TiO ₂ , rare earth oxides, carbides, nitrides, carbonitrides of metals of groups 4a, 5a and 6a of the periodic table;
It is composed of one or more of nitride oxides, silicides, borides and their mutual solid solutions.

When the surface conditioning layer in the sintered body of the present invention has a thickness from the surface of the sintered body to an inside of less than 0.05 mm, the effect of increasing hardness, toughness, wear resistance and heat resistance is obtained. become weak. The thickness of the surface conditioning layer varies depending on the shape or use of the product, but it is 0.05 mm to 3.0 mm from the surface of the sintered body.
It is sufficient that the thickness is 0 mm inside, and it is particularly preferable that the thickness be 0.1 to 2.0 mm inside from the surface of the sintered body.

[0013] The periodic table 3
a, 4a, 5a, 6a group element, Fe, Ni, Co, Si
Compounds containing at least one of the above are those elements
Carbides, nitrides, oxides, borides and their phases
Consisting of at least one of the mutual solid solutions,
It is preferable to be composed of an oxide containing an element.
Is, for example, Y_TwoO_Three, La_TwoO_Three, CeO_Two, Dy_TwoO_Three, T
iO_Two, ZrO_Two, HfO_Two, Nb_TwoO_Five, Ta_TwoO_Five, Cr_Two
O_Three, FeO, Fe_TwoO_Three, CoO, NiO , SiO_Two, And
Complex compounds of these oxides, mutual solid solutions or calcinations
The composite of alumina, which is the main component inside the compact, and the above oxides
Consisting of at least one of a compound compound and a mutual solid solution.
You.

The above compound present in the surface conditioning layer has a concentration gradient from the surface to the inside of the surface conditioning layer. Group 3a, 4a, 5a, 6a element, Fe, Ni, C
At least one diffusion element in o and Si is gradually reduced from the surface toward the inside. In particular, the concentration gradient of the diffusion element is determined by the concentration (Cs) of the diffusion element present in the surface conditioning layer within 0.05 mm from the surface and the diffusion element concentration in the sintered body excluding the surface conditioning layer. Is preferably 1.5 or more (Cs / Ci ≧ 1.5) because the wear resistance, toughness, heat resistance, and fracture resistance of the sintered body are significantly improved. .

The surface conditioning layer has a structure formed on a part or the whole surface of the sintered body, or a structure in which the kind of the compound to be present in the surface conditioning layer differs depending on the surface of the sintered body. In some cases, or in a combination thereof, the configuration of the surface conditioning layer and the thickness of the above-mentioned surface conditioning layer can be properly used depending on the shape and application. Specifically, for example, when the sintered body of the present invention is used as a cutting tool, particularly when used as a throw-away tip, a surface conditioning layer in which different compounds are present is formed on the scooping surface and the flank, respectively. More specifically, the scooping surface has D, which enhances strength, toughness, and heat resistance.
y, Zr, Hf, Cr (garnet, ZrO, respectively)
₂ , HfO ₂ , (Cr, Al) ₂ O _{3 as a} solid solution) and a flared surface with NiO and SiO ₂ (existing as spinel and mullite, respectively) having enhanced abrasion resistance. It is preferable to adopt a configuration of an existing surface conditioning layer.

On the surface of the sintered body having the surface conditioning layer having the above-mentioned structure, carbides, nitrides, oxides, oxides of Al, oxides and nitrides of elements of groups 4a, 5a and 6a of the periodic table are further added. It is more preferable to form a single-layer or multi-layer coating of at least one of these mutual solid solutions or diamond, diamond-like carbon, or cubic boron nitride, because the abrasion resistance and the fracture resistance are improved. .

In the production of the sintered body of the present invention, first, the surface conditioning layer is formed by a prior step of the sintering step, during the sintering step, or during the sintering step in a conventional production process utilizing powder metallurgy. The diffusion element may be penetrated or diffused from the surface of the sintered body after the sintering. However, the following method is particularly preferable because the thickness of the surface conditioning layer and the concentration gradient of the diffusion element can be easily controlled.

That is, the method for producing a sintered body of the present invention
First step of mixing and forming a starting material containing alumina powder as a main component to form a powder compact, and forming a surface of the powder compact on the surface of the periodic table at 3a, 4a, 5a, 6a, iron group metal and Si. Contacting or impregnating a solution of a precursor to form the compound with at least one of the following:
This is a method for producing the above-described sintered body by a process and a third process of heating and sintering in an atmosphere gas or an oxidizing gas.

The powder compact in the first step of the method for producing a sintered compact according to the present invention can be formed by extrusion molding, pressure molding using a mold, injection molding, casting, or the like, which is performed by conventional powder metallurgy. It is a powder compact formed by a molding method or the like.

The step of bringing the surface of the powder compact into contact with the compound in the second step in the method for producing a sintered compact according to the present invention specifically means, for example, the step of bringing the compound powder into contact with the surface of the powder compact. A method of forming the powder compact integrally, a method of applying or spraying the compound powder on the surface of the powder compact, a method of placing the powder compact on a plate coated with the compound powder, or a method of placing the powder compact in the compound powder. The method of burying can be mentioned. The precursor solution for forming a compound in the second step is, for example, Y (NO ₃ ) ₃ , Ti (SO
₄ ) ₂ , ZrO (NO ₃ ) ₂ , CrO ₃ , Co (NO ₃ ) ₂ ,
An aqueous solution of NiCl ₂ can be used.

The compound to be brought into contact with the powder compact in the second step or the precursor to be impregnated may be a compound which forms an oxide by an oxidizing atmosphere gas during sintering.
Examples include carbides, nitrides, sulfides, chlorides and various salts.

The atmosphere gas in the third step of the method for producing a sintered body of the present invention is, for example, TiCl ₄ , CrO ₃ , Ni
A mixed gas of Cl ₂ and N ₂ can be used. Also,
The heat sintering in the third step is performed at a temperature of, for example, 1400 to 1800 ° C. at which the powder compact is densely sintered.

In the case where a hard coating is further formed on the surface of the sintered body having the surface conditioning layer manufactured as described above, the coating must be formed by a conventional CVD method or PVD method. Can be.

[0024]

The sintered body of the present invention has strength, toughness,
It has the effect of increasing the wear resistance and heat resistance, and the concentration gradient of the diffusion element forming the compound in the surface conditioning layer has the effect of relaxing the thermal stress between the surface conditioning layer and the inside of the sintered body. It is. In particular, in the case of a diffusion element of Dy, Zr, Hf, and Cr, the effect of increasing the strength and toughness of the sintered body is strong, and Ni,
In the case of the diffusion element of Si, the effect of enhancing the wear resistance of the sintered body is enhanced.

[0025]

Example 1 α-Al ₂ O _{3 having} an average particle size of about 0.3 μm,
About 0.03 μm of MgO, ZrO ₂ (3 mol% of Y ₂ O
₃ using a commercially available powder of the content), (A) 99.5wt% A
l ₂ O ₃ -0.5 wt% MgO and (B) 80.0 wt
% Al ₂ O ₃ -20.0 wt% ZrO ₂ (3Y), and mixed with a ball made of methanol and Al ₂ O ₃ into a urethane-lined stainless steel pot, mixed and pulverized for 48 hours, and dried. While heating to 80 ° C., 4 wt% of paraffin wax was added and mixed to obtain a mixed powder. Next, the mixed powder was filled in a mold for ISO standard SNMN120408, and a powder compact was produced by applying a pressure of 1 ton / cm ² . The powder compact thus obtained was sintered under the treatment methods and sintering conditions shown in Table 1, and the products 1 to 1 of the present invention were sintered.
0 and comparative products 1 and 2 were obtained.

[0026]

[Table 1] The thus-obtained sintered bodies of the inventive products 1 to 10 and the comparative products 1 and 2 were cut, and the thickness of each surface-treated layer, the surface of the sintered body (0.05 mm inward from the surface of the surface-treated layer) ) And the concentration of the diffusion element at 2.3 mm inside point from the surface of the sintered body. The results are shown in Table 2. The concentration of the diffusion element was measured by EPMA.

Table 2 also shows the results of identifying the color of the surface and the product on the surface by X-ray diffraction.

[0028]

[Table 2] Next, using the products 2, 5, 6, 8, and 9 of the present invention and the comparative products 1 and 2, the work material was S48C, and the cutting speed was 400 m / mi.
n, feed: 0.2 mm / rev, cut: 1.5 m
m, insert shape: SNMN120408 (with breaker, PH 0.15 × -25 °), cutting time: 10 minutes, evaluation: dry turning test with average flank wear width (V _B )
Work material: S48C (with four grooves on the outer circumference), Cutting speed:
100 m / min, depth of cut: 1.5 mm, chip shape: SNMN120408 (with breaker, PH 0.1
(5 × −25 °), cutting time: until the life due to chipping or chipping, evaluation: dry intermittent turning with an average life time of 3 corners was performed. Table 3 shows the results.

[0029]

[Table 3]

[0030]

Example 2 Next, the product 9 of the present invention and the comparative product 2 were
Furnace pressure 10 using a rating device^-3 Ti in Torr
While evaporating the gas, the gas flowing into the furnace is changed to Ar, Ar / N_Two=
50/50, Ar / CH_Four= 50/50
In this way, the coating thickness and coating material
0.5 μm Ti, 1.0 μm TiN, 1.0 μm TiC
Was coated by lamination.

The obtained coated chip (ISO SNMN1)
20408), work material: FCD60, cutting speed: 15
0 mm / min, feed: 0.3 mm / rev, depth of cut: 1.5 mm, cutting time: 20 minutes As a result of performing dry cutting, the average flank wear width of the product 9 of the present invention was 0.15.
mm was normal, whereas Comparative Product 2 was as large as 0.35 mm after 15 minutes cutting and was broken during 17 minutes cutting.

[0032]

The sintered body of the present invention has slightly improved wear resistance and remarkable chipping resistance when used as a cutting tool, as compared with a conventional alumina sintered body in which additives are uniformly dispersed. There is an excellent effect of improving. In addition, the sintered body of the present invention having a hard coating formed thereon has significantly improved wear resistance and chipping resistance when used as a cutting tool, and has a remarkably long life, as compared with a conventional coated alumina sintered body. There is an excellent effect of improving. Further, the sintered body of the present invention can control the color tone of the surface conditioning layer.
Can be diffused from red-violet to pink, from Co to blue-violet to blue, and from Ni to blue-green to green. There is also an effect that can be easily performed.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-117949 (JP, A) JP-A-3-5362 (JP, A) JP-A-62-21776 (JP, A) JP-A-2- 157176 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 35/10 C04B 41/87 C04B 41/89

Claims (5)

(57) [Claims] 1. A part or all of a surface of a sintered body mainly composed of alumina, at least 0.05 m from the surface.
m, a surface conditioning layer is formed to a thickness up to the inside of the metal layer, and the surface conditioning layer includes at least one of elements of Group 3a, 4a, 5a, and 6a of the periodic table, Fe, Ni, Co, and Si. An alumina sintered body containing a compound containing at least one compound, wherein the surface-tempered layer is formed of 3% of the periodic table contained as the compound.
a, 4a, 5a, 6a group element, Fe, Ni, Co, Si
At least one diffusion element is gradually reduced from the surface of the surface-tempered layer toward the inside of the sintered body, and the diffusion element present in the surface-tempered layer within 0.05 mm from the surface is diffused. The ratio of the element concentration (Cs) to the diffusion element concentration (Ci) inside the sintered body excluding the surface conditioning layer is 1.5 or more (Cs / Ci ≧ 1.5). Alumina sintered body for tools. 2. The alumina sintered body for a tool according to claim 1, wherein the compound is an oxide. 3. The surface conditioning layer is formed on at least two surfaces of the sintered body, and the surface conditioning layer is formed on one of at least two surfaces of the sintered body. The alumina sintered body for a tool according to claim 1, wherein the layer contains the compound different from the surface conditioning layer formed on another surface. 4. The surface of the alumina sintered body according to claim 1, 2 or 3, further comprising carbides, nitrides, oxides, oxides and nitrides of elements of groups 4a, 5a and 6a of the periodic table. And at least one of these mutual solid solutions or diamond, diamond-like carbon, cubic boron nitride
An alumina sintered body for a tool, wherein a single-layer or multilayer coating of any kind is formed. 5. An alumina sintered body for a tool, wherein the alumina sintered body for a tool according to claim 1, 2, 3 or 4 is used as a cutting tool.