JPH0691408A - Surface coated ceramic cutting tool superior in chipping resistance - Google Patents

Abstract

PURPOSE:To provide a surface coated ceramic cutting tool for exhibiting a superior chipping resistance against cutting process under severe conditions, such as high-speed cutting of a cast iron, high-speed cutting of a super hard steel and the like. CONSTITUTION:A surface coated ceramic cutting tool is provided by forming physically deposited hard coating layers consisting of one kind of single-layer or two or more kinds of multi-layers while those kinds being, selected among oxide, nitride and carbon-nitride of titunium having mean layer thickness of 0.1-20mum and mean crystal particle diameter of 150-300 angstrom on a ceramic base substance obtained by sintering the raw material powder of a combined composition consisting of 15-45% by weight of one sort or more than two sorts among a group composed of carbide, nitride and oxide of a metal belonging to 4a, 5a and 6a families on the Periodic Table and solid solutions of more than two sorts of these compounds, 0.1-5% of metal in iron family, 0.1-5% of one sort or two sorts among magnesium- and yttrium-oxide and the residue of alminum oxide and unavoidable impurities.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-coated ceramic cutting tool which exhibits excellent fracture resistance against cutting under severe conditions such as high speed cutting of cast iron and high speed cutting of high hardness steel. is there.

[0002]

2. Description of the Related Art Conventionally, for example, JP-A-55-48503.
Aluminum oxide (hereinafter referred to as A
On the surface of a substrate made of a base ceramic (denoted by l ₂ O ₃ ), carbides, nitrides, and carbonitrides of Ti (hereinafter referred to as Ti, respectively) are formed by ordinary physical vapor deposition and chemical vapor deposition.
C, TiN, and TiCN), a surface-coated ceramic cutting tool is known in which a hard coating layer composed of one single layer or two or more multi-layers is formed with an average layer thickness of 3 to 20 μm. There is.

The Al ₂ O ₃ -based ceramics are generally
In% by weight (hereinafter,% means% by weight), one or two of the group consisting of carbides, nitrides and oxides of metals of Groups 4a, 5a and 6a of the Periodic Table and two or more solid solutions thereof. Type or more: 15 to 45%, one or two types of oxides of Mg and Y: 0.1
It is also known that it can be obtained by sintering a raw material powder having a compounding composition containing 5.0% of Al ₂ O ₃ and the balance of Al ₂ O ₃ and unavoidable impurities. It is known that compressive stress acts on the hard coating layer formed by the method, and thus the fracture resistance is improved.

[0004]

On the other hand, the efficiency of cutting machines in recent years has been remarkably high, and there is a tendency for even higher speed cutting and heavy cutting such as high feed and high depth of cut. Although it is desired to improve the characteristics corresponding to this in the cutting tool as well, in the conventional surface-coated ceramic cutting tool described above, peeling of the hard coating layer on the cutting edge is likely to occur with respect to cutting under severe conditions, Due to this, chipping or chipping of the tip of the cutting edge occurs, and the service life is shortened, and it is not possible to deal with it sufficiently.

[0005]

Therefore, the present inventors have
From the above-mentioned viewpoint, as a result of research to develop a surface-coated ceramic cutting tool that can sufficiently cope with cutting even under severe conditions, as a result, it was found that metals of the periodic table 4a, 5a, 6a Carbides, nitrides, oxides, and one or more selected from the group consisting of solid solutions of these two or more: 15 to 45%, one or two of Mg.Y oxides: 0. 1 to
0.1% to 5.0% of an iron group metal is added to an ordinary ceramic obtained by sintering a raw material powder containing 5.0% of Al ₂ O ₃ and the balance of Al ₂ O ₃ and inevitable impurities. Then, the toughness is further improved. Further, when a ceramic containing 0.1 to 5.0% of the iron group metal is used as a substrate and a physical vapor deposition hard coating layer is formed on the surface of the substrate, the adhesion strength of the hard coating layer to the substrate is increased. It was found that the hard coating layer is less likely to peel off even when cutting under severe conditions, and the chipping and chipping of the cutting edge tip due to peeling is drastically reduced. It was.

The present invention has been made on the basis of the above findings, and is based on the group consisting of carbides, nitrides and oxides of metals of groups 4a, 5a and 6a of the periodic table and solid solutions of two or more of these. One or more of them: 15 to 45%, iron group metal: 0.1 to 5%, one or two of oxides of Mg and Y: 0.1 to 5
%, Aluminum oxide and unavoidable impurities: The remainder, which is a composition composition (above weight%) of which is sintered, has a physical vapor deposition hard coating layer formed on the surface of a ceramic substrate and has excellent fracture resistance. And a surface-coated ceramic cutting tool.

The physical vapor deposition hard coating layer has an average crystal grain size of 150 to 300 angstroms and is composed of one kind of a carbide, a nitride and a carbonitride of Ti or two or more kinds of multilayers. , Its average layer thickness is 0.1 to 20 μm
It is preferably within the range.

In the present invention, the reason why the adhesion strength of the hard coating layer is improved by adding the iron group metal to the ceramic substrate is not clear, but the addition of these improves the electrical conductivity in the substrate. Can be considered. Therefore, it is considered that the adhesion strength of the physical vapor deposition hard coating layer is improved.

The physical vapor deposition hard coating layer formed on the surface of the ceramic substrate of the present invention is disclosed in, for example, JP-A-63-263.
Using an activated reactive vapor deposition apparatus utilizing an electron beam, which is one of physical vapor deposition apparatuses as described in Japanese Patent Laid-Open No. 56-56, TiC at a normal vapor deposition rate of about 2 μm (thickness) / hr. , TiN, TiCN, a single layer or two or more layers can be formed.

Further, using the above physical vapor deposition apparatus, the reaction is particularly suppressed, and the vapor deposition rate is remarkably lowered, that is, the reaction is performed for a long time to vapor deposit to a predetermined thickness, specifically, 0.1. When a hard coating layer composed of one single layer of TiC, TiN and TiCN or two or more multiple layers is formed under the condition of vapor deposition at a rate of up to 0.6 μm (thickness) / hr, this results in formation. In the physical vapor deposition hard coating layer thus obtained, the crystal grains became finer, and the crystal grains became finer as the vapor deposition rate became lower, and the grain size was particularly excellent when the average crystal grain size was 300 angstroms or less. Exhibits chipping resistance over a long period of time.

Next, the composition of the Al ₂ O ₃ -based ceramic constituting the substrate of the surface-coated cutting tool of the present invention, and the reasons for limiting the average layer pressure and average crystal grain size of the physical vapor deposition hard coating layer will be described.

A. Composition of Substrate (a) "One or Two of Group 4a, 5a, 6a Group Carbide, Nitride, Oxide, and Solid Solution of Two or More of These" , Al ₂ O ₃ grain growth suppression effect and the effect of improving the thermal shock resistance of the substrate, but the content is 1
If it is less than 5%, the desired effect cannot be obtained, while if it exceeds 45%, the content of Al ₂ O ₃ becomes relatively low, which is excellent due to Al ₂ O ₃ . Further, since the wear resistance is lowered, the content thereof is set to 15 to 45%.

(B) "Iron group metal" The iron group metal means Fe, Co and Ni. These components have the effect of improving the adhesion strength of the physical vapor deposition hard coating layer, but their contents are , Less than 0.1%, the desired effect cannot be obtained on the other hand, while the content is 5.0.
If it exceeds 0.1%, the wear resistance of the substrate will be deteriorated, so the content was set to 0.1 to 5.0%.

(C) "One or Two of Mg and Y Oxides" These components improve the sinterability of the substrate and can be used not only in the conventional hot pressing method but also in normal pressure sintering. Method and hot isostatic pressing method (HIP method) also have the effect of enabling sintering, but if the content is less than 0.1%, the desired effect is obtained for the above-mentioned action. On the other hand, its content is
If it exceeds 5.0%, the wear resistance of the substrate will be deteriorated, so the content thereof was set to 0.1 to 5.0%.

B. Physical vapor deposition hard coating layer (a) Average layer thickness If the average layer thickness is less than 0.1 μm, the desired effect of improving the fracture resistance due to the formation of the hard coating layer cannot be obtained, while if the average layer thickness exceeds 20 μm, the hard coating layer is hard. The peeling of the coating layer is liable to occur, and vapor deposition for a long time is required, resulting in a marked decrease in productivity. Therefore, the average layer thickness was set to 0.1 to 20 μm.

(B) Average crystal grain size If the average crystal grain size exceeds 300 angstroms, the fracture resistance during cutting sharply deteriorates, and especially under severe cutting conditions, chipping and chipping occur on the cutting edge. This is not desirable because it tends to be easy, and therefore the finer the crystal grains, the more desirable for the fracture resistance. However, when the average crystal grain size is less than 150 angstroms, the formation rate of the hard coating layer rapidly decreases. However, it takes a long time to form a film having a predetermined thickness, which is uneconomical. Therefore, the average crystal grain size is preferably 150 to 300 angstroms.

[0017]

EXAMPLES Next, the surface-coated ceramic cutting tool of the present invention will be specifically described by way of examples.

Average particle size: Raw material powders of various components having a predetermined particle size within the range of 0.5 to 3 μm were compounded so as to have the compounding compositions shown in Tables 1 and 2, and 1 with an attritor.
After wet pulverizing and mixing for 0 hours, drying, and press forming into a green compact, the green compact is heated in an Ar atmosphere at a temperature of 1650.
After normally sintering at a predetermined temperature within the range of up to 1800 ° C. for 3 hours to obtain 95% or more of the theoretical density, further, in an Ar gas atmosphere, pressure: 1500 atm, temperature: 1650
HIP treatment was carried out under the condition of holding at 1 ° C. for 1 hour to produce ceramic substrates A to Y having the same composition as the above composition and having a chip shape of SNGN432.

[0019]

[Table 1]

[0020]

[Table 2]

Next, each of these ceramic substrates A to Y was loaded into a physical vapor deposition apparatus using a usual electron beam, and each physical vapor deposition hard coating layer of TiN, TiC and TiCN was formed under the following conditions.

(A) Conditions for forming a TiN physical vapor deposition hard coating layer: furnace temperature: 500 ° C., furnace pressure: 5 × 10 ⁻⁴ Torr, atmosphere: nitrogen, basic potential: −500 V, discharge electrode potential: +50 V

(B) Conditions for forming TiC physical vapor deposition hard coating layer Temperature in furnace: 500 ° C., Pressure in furnace: 2 × 10 ⁻⁴ Torr, Atmosphere: Nitrogen, acetylene, Basic potential: −300 V, Electrode potential for discharge: + 30V,

(C) Conditions for forming TiCN physical vapor deposition hard coating layer Temperature in furnace: 500 ° C., Pressure in furnace: 35 × 10 ⁻⁴ Torr, Atmosphere: Nitrogen, acetylene, Basic potential: −400 V, Electrode potential for discharge: + 35V,

The thickness of the physical vapor deposition hard coating layer on the surface of the ceramic substrate in this apparatus was controlled by adjusting the reaction time, and the average crystal grain size was controlled by adjusting the vapor deposition reaction rate.

Under these conditions, the compositions shown in Tables 3 to 4,
A hard coating layer having an average crystal grain size and an average layer thickness is formed, and the surface-coated ceramic cutting tool of the present invention (hereinafter referred to as the present invention-coated cutting tool) 1 to 17, a comparative surface-coated ceramic cutting tool outside the present invention. 1 to 6 (hereinafter referred to as comparative coated cutting tools) and 1 to 2 of conventional surface-coated ceramic cutting tools (hereinafter referred to as conventional coated cutting tools) were manufactured.

[0027]

[Table 3]

[0028]

[Table 4]

With respect to various coated cutting tools thus obtained, (A) Work material: SNCM439 round bar, cutting speed: 350 m / min. , Sending: 0.3 mm / rev. , Incision: 2 mm, cutting time: 20 minutes, high-speed dry continuous cutting test of steel under the condition (A cutting condition), the flank wear width of the cutting edge was measured, and these measurement results are shown in Table 5 to Table 5. 7 shows.

(B) Work material: SNCM439 having four longitudinal grooves provided at equal intervals along the length direction, cutting speed: 250 m / min. , Sending: 0.15 mm / rev. , Notch: 1.0 mm. Cutting time: 15 minutes, a high-speed dry interrupted cutting test of steel under the condition (B cutting condition) was performed to measure the flank wear width of the cutting edge, and the measurement results are shown in Tables 5 and 6. .

[0031]

[Table 5]

[0032]

[Table 6]

[0033]

From the results shown in Tables 1 to 6, the coated cutting tools 1 to 17 of the present invention are more resistant to peeling of the hard coating layer on the cutting edge than the conventional coated cutting tools 1 and 2 under severe cutting conditions. It can be seen that no fracture occurs and therefore no chipping or chipping occurs in the cutting edge, and excellent fracture resistance is exhibited for a long period of time. Further, the comparative coated cutting tools 1 to 6 which deviate from the conditions of the present invention (values deviating from the conditions of the present invention are marked with *) are also deteriorated in characteristics as cutting tools. I understand. Therefore, the surface-coated ceramic cutting tool of the present invention exhibits excellent cutting characteristics and can greatly contribute to the development of industry.

Claims (3)

[Claims] 1. One or more members selected from the group consisting of carbides, nitrides and oxides of metals of groups 4a, 5a and 6a of the periodic table and solid solutions of two or more members thereof: 15 to 45%, iron group Metal: 0.1 to 5%, one or two kinds of Mg and Y oxides: 0.1 to 5
%, Aluminum oxide and unavoidable impurities: the rest, a ceramic powder obtained by sintering a raw material powder having a compounding composition (above wt%) consisting of one of Ti carbide, nitride, and carbonitride. A surface-coated ceramic cutting tool having excellent fracture resistance, which is formed by forming a physical vapor deposition hard coating layer consisting of a single layer or a multilayer of two or more types. 2. The surface-coated ceramic cutting tool with excellent fracture resistance according to claim 1, wherein the average layer thickness of the physical vapor deposition hard coating layer is in the range of 0.1 to 20 μm. 3. The surface-coated ceramic cutting tool with excellent fracture resistance according to claim 1 or 2, wherein an average crystal grain size of the physical vapor deposition hard coating layer is within a range of 150 to 300 angstroms. .