JPH1094905A - Surface coated ceramic tools - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface-coated ceramic tool excellent in adhesion strength between a ceramic coating layer and a tool base, and further excellent in wear resistance and fracture resistance. SOLUTION: A surface-coated ceramic tool 1 includes a tool base 3 made of ceramic and a ceramic coating layer 2 formed in a single layer or a plurality of layers covering the surface of the tool base 3 by a vapor deposition method. The electrical resistivity of ceramics constituting the tool base 3 is set to 1 Ω · cm or less. The ceramic coating layer 2 is formed by adhering (or depositing) components to be included in the ceramic coating layer 2 to the charged tool base 3 in the form of charged particles such as ions. As a result, the adhesion between the ceramic coating layer 2 and the tool base 3 can be significantly increased, and a surface-coated ceramic tool having excellent wear resistance and chipping resistance can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a surface-coated ceramic tool.

[0002]

2. Description of the Related Art Conventionally, CBN (cubic boron nitride) tools have been used in order to increase the processing efficiency of hardened materials such as carburized hardened steel, die steel, and tool steel. However, CB
Although the N tool has excellent cutting performance, it is very expensive, so there is a strong demand among users for the development of a ceramic tool which is inexpensive and has a performance comparable to a CBN tool.
Therefore, for example, Japanese Patent Application Laid-Open Nos. Hei 4-289002 and Hei 5
As disclosed in JP-A-69205, a relatively inexpensive ceramic such as alumina-titanium carbide is used as a tool base, and a ceramic coating made of alumina, titanium carbide, carbide of an alloy of titanium and aluminum or the like is formed on the surface of the tool base. A technique for providing a tool having excellent wear resistance has been disclosed.

[0003]

In the above-mentioned tool, a physical vapor deposition method such as high-frequency sputtering is used as a method for forming a ceramic coating on a tool base. Here, the ceramic coating formed by the physical vapor deposition method tends to have low adhesion strength due to a low processing temperature (up to 600 ° C.). There was a problem that the film was self-destructed by the stress. Therefore, various measures have conventionally been taken in order to improve the adhesion strength of the coating by such a physical vapor deposition method. For example, prior to film formation, for example, the surface of the substrate is cleaned by sputter cleaning using gas ions such as Ar or H ₂ gas, or bombard cleaning using metal ions such as Ti, or the composition of the film is inclined. For example, methods of reducing the compressive stress in the film are exemplified, but the adhesion strength achieved by these methods is not necessarily sufficient.

[0004] It is an object of the present invention to provide a surface-coated ceramic tool having excellent adhesion strength between a ceramic coating and a tool base, and further excellent wear resistance and fracture resistance.

[0005]

In order to solve the above-mentioned problems, a surface-coated ceramic tool according to the present invention comprises a tool base made of ceramics and a tool base formed by a vapor phase film forming method. And a ceramic coating layer formed in a single layer or a plurality of layers covering the surface, wherein a ceramic constituting the tool base has an electrical resistivity of 1 Ω · cm or less.

In the configuration of the above-described tool, the tool base is made of ceramics having an electric resistivity of 1 Ω · cm or less, and the tool base can be easily charged positively or negatively during film formation. Then, a component to form the ceramic coating layer is attached (or deposited) to the charged tool base in the form of charged particles such as ions, thereby forming a ceramic formed on the basis of the attachment of the component. The adhesion between the coating layer and the tool substrate can be significantly increased, and as a result, a surface-coated ceramic tool excellent in wear resistance and fracture resistance can be realized.

Specifically, the ceramic coating layer forms a gas phase on the surface of a tool substrate charged with one or more types of ions to be a constituent of the ceramic coating layer in the opposite polarity to the ions. It can be formed by adhering through the interface. An ion plating method can be exemplified as a typical vapor phase film forming method for forming such a film.

Here, if the electrical resistivity of the ceramics constituting the tool base exceeds 1 Ω · cm, the tool base is likely to be polarized by applying a voltage, and it becomes difficult to form a required charged state. It becomes impossible to secure a sufficient adhesion between the formed ceramic coating layer and the tool base. It is more preferable to use ceramics having an electric resistivity of 0.7 Ω · cm or less.

The ceramic constituting the tool base is desirably a fired body having an average crystal grain size of 1 μm or less. If the average crystal grain size of the fired body exceeds 1 μm, it may be difficult to maintain the value of the electric resistivity at 1 Ω · cm or less. For example, as described later, when a fired body in which insulating ceramic particles such as alumina and conductive ceramic particles such as TiN are mixed is used, if the average crystal grain size of the fired body exceeds 1 μm, the average particle diameter of the conductive ceramic particles is increased. The diameter also increases, and a detour easily occurs in the conductive path of the fired body formed by the series, and the value of the electrical resistivity increases. The average crystal grain size of the fired body is more desirably 0.7 μm or less. On the other hand, the ceramic constituting the tool base has a Vickers hardness of 200.
Desirably, the sintered body is 0 kg / mm ² or more. If the Vickers hardness of the fired body is less than 2000 kg / mm ² , the wear resistance required for a tool cannot be secured. The fired body more desirably has a Vickers hardness of 2
It is preferable to use a material of 100 kg / mm ² or more.

Next, ceramics constituting the tool base are mainly composed of alumina, and are further composed of Ti, V,
Cr, Al, Zr, Nb, Mo, Hf, Ta and W carbides, nitrides and carbonitrides (eg, TiC, TiN,
A composite fired body containing one or more of TiCN, TaC, WC, etc.) in a total amount of 20 to 40% by weight can be used. In the composite fired body, the carbide, nitride, and carbonitride particles function as the conductive ceramic particles described above, and a continuous path forms a conductive path of the fired body. The strength of the fired body formed is increased. By using such a composite fired body, it is possible to obtain a tool base that satisfies the above-described condition of the electric resistivity required for the present invention and has sufficient strength.

If the total content of the above-mentioned carbides, nitrides and carbonitrides is less than 20% by weight, the electrical resistivity of the fired body cannot be maintained at 1 Ω · cm or less. On the other hand, 40
If the content is more than 10% by weight, sinterability decreases, and it becomes difficult to obtain a dense fired body, and a tool base having sufficient strength cannot be obtained. The total content of carbide, nitride and carbonitride is more preferably adjusted in the range of 25 to 35% by weight.

The composite fired body constituting the tool base includes:
A sintering aid can be added in the range of 0.2 to 5.0% by weight. Examples of the sintering aid include rare earth oxides such as Y ₂ O ₃ and one or two of MgO, CaO, SiO _{2 and the} like.
More than one species can be used. If the amount of the sintering aid is less than 0.2% by weight, the effect of adding the aid on densification of the fired body cannot be sufficiently obtained. In addition, 5.0% by weight
If it exceeds, crystal grain growth occurs, leading to a decrease in the strength of the fired body. In addition, the addition amount of the sintering aid is more desirably adjusted in the range of 0.5 to 1.5% by weight.

The ceramic coating layer is made of Ti, V, C
It can be mainly composed of one or more of carbides, nitrides and carbonitrides of r, Al, Zr, Nb, Mo, Hf, Ta and W. The ceramic coating layer made of this material has excellent adhesion to the fired body and high adhesion,
It also has high hardness and excellent wear resistance. The ceramic coating layer may be formed as only one layer or may be formed as a plurality of layers. In the latter case, if the material is different between at least some of the plurality of layers. You may make it do. When such a ceramic coating layer is formed by, for example, an ion plating method, for example,
The constituent metal source metal is evaporated to a gas phase by a known method such as resistance heating, electron beam heating, sputtering, or arc evaporation, and nitrogen gas or methane gas serving as a nitrogen or carbon component source is added thereto. Introduce and mix,
Further, a method of ionizing by a known method such as glow discharge, corona discharge, high-frequency discharge, microwave discharge or the like and attaching these ions to the charged surface of the tool base can be adopted.

The ceramic coating layer has a total thickness of 0.1 mm.
It is desirable that the thickness be in the range of 5 to 5 μm. If the total thickness is less than 0.5 μm, the life of the tool will soon expire with only a slight wear of the coating layer. On the other hand, if the total thickness exceeds 5 μm, the residual stress in the film increases, and problems such as peeling are likely to occur. The total thickness is more desirably adjusted in the range of 0.5 to 2 μm.

Incidentally, the ceramic coating layer is, specifically,
It can be constituted as a single layer having a thickness of 0.5 to 2 μm mainly composed of TiN. Such a coating layer is excellent in adhesion strength and abrasion resistance while being a single layer, and is easy to manufacture. Further, while the ceramic coating layer shows a bright color tone close to golden color, when the tool base is made of the above-described composite fired body, it becomes a black color tone. Also, when the wear of the ceramic coating layer progresses and the tool base portion serving as the base is exposed, there is an advantage that this can be easily determined.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below with reference to examples shown in the drawings. FIG. 1 shows a turning tool chip 1 (hereinafter also simply referred to as a chip) as one embodiment of a surface-coated ceramic tool of the present invention. As shown in FIGS. 1A and 1B, the chip 1 has a structure in which the entire outer surface of a tool base 3 formed in a flat and substantially triangular prism shape is covered with a ceramic coating layer 2. The main surface 1c forms a rake surface, and the side surface 1e forms a flank surface. As shown in FIG. 1C, the corners 1a of the chip 1 are rounded, and the edges 1b are chamfered. As shown in FIG. 1A, a screw insertion hole 1d for mounting the chip 1 in a chip holder (not shown) is formed in the center of the main surface 1c so as to penetrate in the thickness direction.

The tool base 3 is mainly composed of alumina, and further includes Ti, V, Cr, Al, Zr, Nb, Mo,
1 of carbides, nitrides and carbonitrides of Hf, Ta and W (for example, TiC, TiN, TiCN, TaC, WC, etc.)
It is configured as a composite fired body containing 20 to 40% by weight, preferably 25 to 35% by weight of a total of two or more kinds, and optionally, a rare earth oxide such as Y ₂ O ₃ as a sintering aid. And one or two of MgO, CaO, SiO _2, etc.
0.2 to 5.0% by weight, preferably 0.5 to
It is added in the range of 1.5% by weight. And the average crystal grain size is 1 μm or less, preferably 0.7 μm,
Electric resistivity is 1Ω · cm or less, preferably 0.7Ω · c
m. In addition, its Vickers hardness is 20
00kg / mm ² or more, preferably is adjusted at 2100 kg / mm ² or more.

The ceramic coating layer 2 is made of Ti, V,
A coating layer composed of a single layer or a plurality of layers mainly composed of one or more of carbides, nitrides and carbonitrides of Cr, Al, Zr, Nb, Mo, Hf, Ta and W. Having a total thickness of 0.5 to 5 μm, preferably 0.5
The thickness is adjusted in a range of about 2 μm (in FIG. 1, the thickness of the ceramic coating layer 2 is exaggerated). In the present embodiment, the ceramic coating layer 2 is specifically configured as a single layer mainly composed of TiN and having a thickness of 0.5 to 2 μm.

Hereinafter, an example of a method for manufacturing the tool tip 1 will be described. First, alumina powder, the above carbide,
A predetermined amount of raw material powders such as a nitride or carbonitride powder and a sintering aid powder are blended, a binder is added and mixed as necessary, and the mixture is press-formed (by a cold isostatic pressing method). ) Or a known method such as injection molding to produce a green molded body, and the molded body is fired in a predetermined furnace to obtain the tool base 3. In addition, you may perform the calcination by a hot isostatic press method instead of the said method, or following the calcination by the said method.

Next, a ceramic coating layer 2 is formed on the surface of the tool base 3 by an ion plating method. FIG. 2 (a) conceptually shows an example of an arc ion plating apparatus, in which a turntable type substrate holder 31 is disposed in a chamber 10 and a tool base 3 is fixed thereto, while facing the same. Then, one or a plurality of metal targets 33 as evaporation sources are provided.
2 are connected. The chamber 10 has an exhaust port 10
The gas is exhausted under reduced pressure from a, and nitrogen gas as a reaction gas is introduced from the gas inlet 13. In this state, a voltage is applied to the tool base 3 and the metal target 33 by the DC power supplies 32 so as to be negatively charged, respectively, and the level of each applied voltage is relatively positive on the metal target 33 side.
The adjustment is performed so that the tool base 3 side is relatively negative. As a result, an arc discharge is generated between the metal target 33 and the tool base 3, and the heat generated by the arc discharge causes the metal target 33 to move.
While the metal raw material constituting
The metal raw material and the nitrogen gas evaporated by the potential gradient between the tool base 3 and the tool base 3 are ionized and adhered and deposited on the surface of the tool base 3 to thereby form the ceramic coating layer 2 mainly composed of TiN (FIG. 1). ) Is formed.

On the other hand, FIG. 2 (b) conceptually shows an example of a resistance heating evaporation type ion plating apparatus.
The tool base 3 is fixed via a substrate holder (not shown) disposed in the chamber 10, and a boat-like resistance heating filament 11, for example, is provided at a position substantially opposed to the tool base 3, and a metal component of the ceramic coating layer 2 is provided here. A metal material (Ti metal in this embodiment) M as a source is arranged. Then, the inside of the chamber 10 is
While evacuation is performed from a, the resistance heating filament 11 is energized by the heating power supply 12 to heat and evaporate the metal raw material M, and nitrogen gas as a reaction gas is introduced from the gas inlet 13. Then, in this state, a bias voltage is applied by the DC power supply 14 so that the resistance heating filament 11 side is positive and the tool base 3 side is negative, thereby ionizing the evaporated metal raw material and nitrogen gas. By adhering and depositing on the surface, a ceramic coating layer 2 (FIG. 1) mainly composed of TiN is formed.

As shown in FIG. 3, the tool base 3 is accommodated in a cylindrical container 18 formed of a metal mesh or a perforated metal plate in a chamber, and the tool base 3 is placed in a motor 19a.
The ceramic coating layer 2 (FIG. 1) can also be formed by charging the tool base 3 via the container body 18 while rotating the tool base 3 in the circumferential direction by the rotation mechanism 19 including. Thereby, the ceramic coating layer 2 can be uniformly and efficiently formed on the entire outer surface of the tool base 3.

[0023]

Embodiments of the present invention will be described below. (Example 1) A1 ₂ 0 ₃ powder (average particle size 0.5 [mu] m), T
iC, TiCN and TiN powder (average particle size 1 [mu] m), MgO powder as sintering aids (average particle size 0.2 [mu] m) and Y ₂ 0 ₃ powder were blended (average particle size 1 [mu] m) at various compounding ratio mill The mixture was wet-mixed, and then dried to obtain a raw material powder, which was subjected to press molding at a pressure of ² ton / cm ² to obtain a predetermined molded product. next,
This molded body is heated to a temperature of 1700 to 1 in an inert gas atmosphere.
Pre-baked at 800 ° C for 2 hours, and further at a temperature of 1500 ° C,
After performing HIP processing at a pressure of 1500 atm for 2 hours, the obtained fired body was ground into a shape shown in FIG. 1 to obtain a tool base. The dimensions of the tool base were a flat approximately triangular prism having a thickness of about 4.76 mm and one side of about 13.5 mm, and the radius R of the corner 1a was about 0.8 mm. Further, the chamfered portion provided to the edge portion 1b is shown in FIG.
As shown in the figure, the width t on the main surface 1c side is about 0.2 mm,
It was formed so that the inclination angle θ with respect to c was about 25 °.

The density of the tool substrate thus obtained was measured by the Archimedes method, and the electrical resistivity was measured by the DC four-terminal method. The average particle size was calculated based on a micrograph of the structure by SEM, and the Vickers hardness was measured by a predetermined Vickers hardness meter. On the other hand, the composition of each tool base was analyzed by EDS. The above results are shown in Table 1 (Example: Sample No.
1 to 5) and Table 2 (Comparative Example: Sample Nos. 11 to 15).

Next, a 2 μm-thick TiN layer as a ceramic coating layer was formed on the surface of each of the obtained tool bases 3 using an existing arc ion plating apparatus to obtain a tool tip. The conditions of the ion plating were as follows: arc current: 100 A, bias voltage to the tool base:
-100 V, atmospheric pressure: 1 × 10 ^-2 torr, film forming speed:
It was about 0.1 μm / min. Then, the adhesion strength of the TiN layer 2 to each of the obtained tool tips was measured using a scratch tester. That is, as shown in FIG. 4, a diamond indenter 25 for measuring Vickers hardness is connected to the TiN layer 2.
, And while moving the indenter 25 along the TiN layer 2 while increasing the load L applied to the indenter 25, the TiN layer 2
The adhesive strength was evaluated by the load at which breakage or peeling began to occur (scratch critical load). The surface roughness of the measurement surface of the sample was set to 0.8 μm Rmax, and the load L was controlled so as to increase at a rate of 10 N (Newton) per 1 mm of the moving distance of the indenter 25. The results are shown in Tables 1 and 2.

[0026]

[Table 1]

[0027]

[Table 2]

As is clear from the above results, the tool tip according to the embodiment of the present invention (Table 1) has a better adhesion strength of the TiN layer than the tool tip of the comparative example (Table 2). I understand.

(Example 2) Using the tool base of No. 2 and the existing arc ion plating apparatus, each ceramic coating layer shown in Table 3 was formed in various thicknesses (Sample Nos. 21 to 34), and their adhesion strength was measured in Example 1. The evaluation was performed in the same manner as described above. Table 3 shows the results.

[0030]

[Table 3]

That is, when the thickness of the ceramic coating layer is 5 μm or less, good adhesion strength is maintained. However, when the thickness exceeds 5 μm, the adhesion strength decreases and peeling or the like occurs. Note that the ceramic coating layer has particularly good adhesion strength when the thickness is 2 μm or less.

(Embodiment 3) The tool tip prepared in Embodiments 1 and 2 was used, and in FIG.
Using c as a rake face and side face 1e as a flank face, a turning test was performed under the following conditions. As the tool tips of the examples, the sample Nos. 21, 22, 2
Sample Nos. 4 and 25 in Table 2 were used as the tool tips of Comparative Example.
o. 13 and 14 were used. Work material: SCM415 carburized hardened material (Hv: 850-850)
700) Cutting speed: 200m / min Feeding speed: 0.1mm per rotation Cutting depth: 0.3mm

[0033] Then, after 30 minutes turning under the above conditions, the average flank wear of each chip (average width in Turning direction of wearing region occurring flank 1e: V _B wear amount) was measured. Table 4 shows the results.

[0034]

[Table 4]

That is, in the tool tip according to the embodiment of the present invention, the ceramic coating layer does not peel off,
Also it can be seen that V _B wear amount is small.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a tool tip as an embodiment of a surface-coated ceramic tool of the present invention, a schematic side sectional partial view, and a partially enlarged perspective view.

FIG. 2 is a conceptual diagram illustrating an example of an ion plating apparatus.

FIG. 3 is a conceptual diagram showing a modified example of the same.

FIG. 4 is an explanatory diagram of a scratch test method.

FIG. 5 is a schematic side sectional view showing an enlarged edge portion of the tool tip.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Turning tool tip (surface-coated ceramic tool) 2 Ceramic coating layer 3 Tool base

Claims (7)

[Claims] 1. A tool base comprising: a tool base made of ceramics; and a ceramic coating layer formed in a single layer or a plurality of layers covering a surface of the tool base by a vapor deposition method. Has an electrical resistivity of 1
A surface-coated ceramic tool characterized by being Ω · cm or less. 2. The ceramic coating layer according to claim 1, wherein ions to be constituents of the ceramic coating layer are attached to a surface of the tool base charged to a polarity opposite to that of the ions via a gas phase. Claim 1 which is formed
The described ceramic tool. 3. The ceramic tool according to claim 1, wherein the ceramic constituting the tool base is a fired body having an average crystal grain size of 1 μm or less. 4. The ceramic tool according to claim 1, wherein the ceramic forming the tool base is a fired body having a Vickers hardness of 2000 kg / mm ² or more. 5. The ceramic constituting the tool base is mainly composed of alumina, and further comprises Ti, V, C
One or more of carbides, nitrides and carbonitrides of r, Al, Zr, Nb, Mo, Hf, Ta and W are 2 in total
The ceramic tool according to any one of claims 1 to 4, which is a composite fired body containing 0 to 40% by weight. 6. The ceramic coating layer is made of Ti, V, C
6. The method according to claim 1, wherein one or more of carbides, nitrides and carbonitrides of r, Al, Zr, Nb, Mo, Hf, Ta and W are mainly constituted. Ceramic tools. 7. The ceramic tool according to claim 6, wherein said ceramic coating layer is formed as a single layer mainly composed of TiN and having a thickness of 0.5 to 2 μm.