JP2002337005A - Abrasive-resistant coating coated tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hard coating coated tool capable of simultaneously attaining significantly high oxidation resistance, wear resistance, lubricity, and adhesion for the accommodation of drying and high speed in cutting highly hard steel, and a complex hard coating coated tool capable of attaining further high adhesion by a combination with a conventional coating. SOLUTION: In this abrasive-resistant coating coated tool formed by coating a base surface with a hard coating, the coating is formed by applying coating of at least one layer A, which has chemical composition expressed by (Cra Si1-a )(Nx B1-x ), where 0.5<=a<1, 0.5<=x<=1 and which is composed of a phase relatively rich in Si and a layer A having a phase poor in Si and (CrAl)N series coating. In the layer A, an amolphous microcrystal (Cra Si1-a )(Nx B1-x ) is interposed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hard film-coated tool used for high-speed cutting of high hardness steel.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. Sho 62-56565 discloses the direct cutting of tempered steel for the purpose of improving the efficiency of metal working.
TiAlN represented by JP-A-2-194159
Coatings have been developed and applied to cutting tools. TiAlN
Since the coating has better oxidation resistance than TiN and TiCN, the performance of the cutting tool is remarkably improved in cutting of tempered steel whose cutting edge reaches a high temperature.

However, in recent years, in order to meet the demand for higher efficiency and higher precision of processing, dry cutting has been regarded as important in view of environmental problems and reduction of processing cost in addition to increasing the cutting speed. I have. In such a cutting environment, the welding phenomenon between the wear-resistant film coated on the cutting tool surface and the material to be cut (hereinafter referred to as a work material) has a great effect on the cutting performance, and the cutting temperature also increases. Has become even higher temperature and oxidation resistance is not sufficient even with a TiAlN-based film. That is, the conventional TiN, TiCN
In such a severe cutting environment, the TiAlN film cannot obtain sufficient cutting performance due to an increase in frictional resistance and the progress of oxidation caused by a welding phenomenon with a work material and the like, and wear progresses due to oxidation. The current situation is that it has not been possible to sufficiently control the situation.

In order to solve such a problem, molybdenum disulfide disclosed in JP-A-11-502775 and JP-A-7-164211 are disclosed from the viewpoint of improving the welding resistance.
The cutting tool has been developed in which a lubricating film consisting of tungsten carbide and diamond-like carbon is laminated on the outermost surface of the hard film, but the adhesion of the hard film is poor and the film itself is very brittle. It is poor in oxidation resistance, and cannot be adequately treated in the above cutting environment due to peeling or destruction during cutting, oxidative wear and the like.

From the viewpoint of improving oxidation resistance, Japanese Patent Application Laid-Open
Although there is a case where a third component is added to TiAlN as typified by JP-A-237010 and JP-A-10-130620, the improvement in oxidation resistance that is sufficiently satisfied only by the addition of the third component is not achieved. The reality is that it has not been realized. Japanese Patent Application Laid-Open No. 8-118106 discloses Ti
Although the case of SiN has been proposed, mere TiSiN has not been able to improve the oxidation resistance.

Further, Japanese Patent Application Laid-Open No. 11-138038 discloses
Si inside the hard coating so that₃N ₄With particles
In some cases, Si₃N₄Oxidation proceeds via grain boundaries
Therefore, sufficient oxidation resistance has not been imparted.

[0007]

In view of these circumstances, the present invention provides a hard layer which can cope with dry and high-speed cutting, that is, which has excellent oxidation resistance and low adhesion to a work material. It is an object of the present invention to provide a wear-resistant film-coated tool capable of simultaneously realizing oxidation resistance and welding resistance and capable of cutting high-hardness steel dry at high speed.

[0008]

The inventor of the present invention has conducted detailed studies on the wear resistance of a hard coating, its effect on various work materials and reduction of frictional resistance, and the layer structure of the coating.
Imparting adhesion resistance _{(Cr a Si 1 - a)} (N x B 1 -
_x ), provided that 0.5 ≦ a <1.0 and 0.5 ≦ x ≦ 1.0
Improve the welding resistance by coating the layer A consisting of the chemical composition shown in the above, and further control the crystal morphology to obtain a hard film coated tool with both oxidation resistance and wear resistance. As a result, the present inventors have found that the performance of a cutting tool is extremely excellent in dry high-speed cutting of high hardness steel, and have reached the present invention. Further, by using a hard layer mainly composed of Cr and Al as a base layer in order to further improve the adhesion, a coated tool having more excellent cutting performance is realized. It is desirable that the abrasion resistant film is coated by a physical vapor deposition method.

[0009]

First, the function of each component of the layer A will be described in detail. CrN is originally known as a film having lubricity, and its coefficient of friction is around 0.6. _{(Cr a Si 1 - a)} (N x B 1 - x), where
A nitride or boride composed of Cr and Si having a chemical composition represented by 0.5 ≦ a <1.0 and 0.5 ≦ x ≦ 1.0 is used in steel at room temperature in the atmosphere. Has a low friction coefficient of 0.4, which is lower than that of the conventional TiAl nitride film of 0.8 and that of CrN of 0.6, but at high temperatures, the value further decreases to about 0.2. It was confirmed that this was caused by the fact that Si in the film was diffused inside the film surface at a high temperature due to a reaction with the cutting powder, and a low melting point Si oxide was formed on the film surface.

The low melting point Si oxide makes the (Cr _a S
_{i 1 - a) (N x} B 1 - x) film is further lubricity imparted to the lubricating characteristic of the CrN itself, acts as an excellent lubricating film significantly characteristics, suppresses the increase in the cutting resistance due to the welding action Has been confirmed. Furthermore, it has been clarified that the addition of boron causes boron to form a BN phase inside the film, and the lubricating action of the BN phase further improves the lubricity.

[0011] For improving the oxidation resistance, the present inventors have a result of intensive _{studies, (Cr a Si 1 - a} ) (N x B 1 - x)
The crystal morphology of the phase has a great influence on the oxidation resistance, and by controlling the crystal morphology, it is possible to impart oxidation resistance superior to (TiAl) N-based coatings, which are generally said to have excellent oxidation resistance. That led to the surprising finding. _{(Cr a Si 1 - a)} (N x B 1 - x) phase have different crystal form by ion energy during coating, if a low ion energy exhibited an overall columnar crystals, _Si 3 _{N 4} therein It is in the form of intervening particles. When the ion energy is high, the overall state is close to an amorphous state, and the state of bonding of Si and N is confirmed in CrNB. When the ion energy is moderate and the coating temperature is 550 ° C or higher, completely amorphous CrS
The iBN phase exists in the form of fine crystals, and the SSi of the CrSiBN phase
The i content is determined by the amount of Si in the CrSiBN phase serving as the matrix.
It was confirmed that the form became richer than the amount. It was confirmed that when the temperature was low, a crystal form similar to that when the ion energy was high was exhibited. The reason for the correlation between temperature, ion energy and crystal morphology requires future physical studies.

In particular, when the completely amorphous CrSiBN phase exists as fine crystals, the crystal grain boundaries become very aligned grain boundaries, have few defects, remarkably suppress diffusion of oxygen at the grain boundaries, and have excellent oxidation resistance. It was confirmed to have. At the same time, by interposing fine crystals, the matrix was strengthened in lattice strain, the hardness was improved, and as a result, the wear resistance was also improved. Further, the outermost surface has a Cr of 1 to 5 nm.
Was formed, resulting in even more excellent oxidation resistance.

The coating conditions are such that the ion energy is relatively moderate, the applied bias is -100 V to -150 V, the reaction pressure is about 1 Pa to 5 Pa, and the coating temperature is 550.
C. or higher is a preferable range.

The composition of the metal element of the layer A constituting the hard coating of the present invention is such that in (Cr _a Si _1-a ), the value of a satisfies the expression 0.5 ≦ a <1.0. is necessary. When the value of a is less than 0.5, the Si content becomes too large, the toughness of the film itself is deteriorated, and the internal destruction of the film and the peeling of the film accompanying the destruction become remarkable in dry high-speed cutting, and sufficient performance is obtained. Can not be demonstrated.

[0015] In the case of nitrides or窒硼product according to the A _layer, it is necessary to satisfy 0.5 ≦ x ≦ 1.0 with N _{x B 1-x,} the value of x is 0. If less than 5,
The hardness of the coating is significantly increased, the residual compressive stress is increased, and the adhesion of the coating is deteriorated, so that sufficient cutting performance is not exhibited.

If the fine crystal grain size of the amorphous CrSiBN phase exceeds 500 nm, the effect of lattice distortion is small and the contribution to improving the hardness of the film is reduced, so that it is more preferably 500 nm or less.

It is needless to say that the same effect can be expected even if the third metal component is added to the underlying (CrAl) -based hard layer used here.

The method of coating the hard film-coated tool of the present invention is not particularly limited, but in consideration of the thermal effect on the coated base material, the fatigue strength of the tool, the adhesion of the film, etc. Arc discharge ion plating that can be coated at a relatively low temperature and compressive stress remains in the coated film,
Alternatively, a physical vapor deposition method of applying a bias voltage to the coated substrate side such as sputtering is preferable.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. A
Evaporation of metal components using the ion plating system
The source is a target made of various alloys and a reaction gas.
N ₂Select a gas that provides the desired film from the gas,
Conditions of 600 ° C. substrate temperature and 3.0 Pa reaction gas pressure
, 2 blades made of cemented carbide with an outer diameter of 10 mm, which is the coated substrate
-130V for end mills and cemented carbide inserts
Apply a potential to form a film so that the total thickness of all films is 3 μm
did. Boron and Si are necessary for the target which is the evaporation source
Was added. Table 1 shows the prototypes of the present invention and comparative examples.
You. In the case of a multilayer, the total thickness of layer A is 1.5 μm, and the total thickness of other layers is 1.5 μm.
The coating was evenly applied to 1.5 μm. As shown in the comparative example (C
rSi) N coatings are coated at 450 ° C
This is the case of a simple solid solution without intervening nano-crystals.

[0020]

[Table 1]

A cutting test was performed using the obtained hard-coated end mill and hard-coated insert. The tool life was defined as the cutting length when the tool could not be cut due to chipping or wear of the cutting edge. Table 1 also shows the obtained results. The cutting specifications are shown below.

The cutting conditions of the two-flute carbide end mill are side cutting down cut, work material S50C (hardness HB22).
0), incision Ad10mm × Rd1mm, cutting speed 2
50 m / min, feed 0.06 mm / tooth, and use of air blow.

The insert cutting conditions are as follows: Tool shape SEE4
2TN, 100mm width x 250mm length chamfering,
Work material SKD61 (hardness HRC45), depth of cut 2.0
mm, cutting speed 150m / min, feed 0.15mm /
rev, dry cutting. Table 1 also shows the test results.

The oxidation resistance was evaluated by the thickness of the oxide layer formed when each of the films was coated with a film having a total thickness of 2.5 μm and kept at 900 ° C. in the atmosphere for 1 hour. The coefficient of friction was measured by a general ball-on-disk method using a ball of SKD61 at 600 ° C. Table 2 shows the results.

[0025]

[Table 2]

Comparative Examples 16 and 17 are comparative examples in which the amount of Si or boron is too large. Although the static evaluation values are satisfied, the adhesion is not sufficient and the tool life is short. Comparative Examples 19 and 20 are cases where the layer A is a simple solid solution. Comparative Examples 13, 14, and 15 are examples in which the third component was added to the TiAlN-based coating, and although the oxidation resistance was improved, the improvement effect was less than that of the present invention.

On the other hand, the examples of the present invention are excellent in static evaluation characteristics and also excellent in adhesiveness, and are free from abnormal wear, film oxidative wear and film peeling due to the welding phenomenon. Tool life is significantly improved. Therefore, the present invention is sufficient for dry high-speed cutting of high hardness steel.

[0028]

As described above, the hard-coated tool of the present invention has excellent high adhesion, low friction and high oxidation resistance at the same time as the conventional coated tool. A long tool life can be obtained, which is extremely effective in improving productivity in cutting.

[Brief description of the drawings]

Figure 1 is the present invention embodiment _{(Cr a Si 1 - a)} (N
_x B ₁ - _x) fine amorphous crystals interposed in the matrix _{(Cr a Si 1 - a)} (N x B 1 - x) TEM of
An image is shown.

FIG. 2 is a diagram corresponding to spot 1 in FIG.
_{a Si 1 - a) (N} x B 1 - shows a _x) nanobeam electron diffraction image of the matrix.

FIG. 3 is a view corresponding to the spot 2 in FIG. 1 (Cr
_{a Si 1 - a) (N} x B 1 - x) fine amorphous crystal _{(Ti a Si 1 - a)} (N x B 1 - shows the _x nanobeam electron diffraction image of).

Claims (3)

[Claims] 1. A hard coating, (Cr _a Si
_{1 - a) (N x B} 1 - x), where, 0.5 ≦ a <1,
In a wear-resistant coating-coated tool coated with at least one layer A having a chemical composition represented by 0.5 ≦ x ≦ 1, the A layer is a relatively Si-rich CrSi (N _x B _{1 -x} ) phase. When less relatively _{Si CrSi (N x B 1 -} x) is composed of a phase, nitride layer other than the a layer is composed mainly of Cr and Al, carbonitride, oxynitride, nitride A wear-resistant film-coated tool, wherein two or more boride layers are laminated. 2. A wear-resistant coating coated tool according to claim 1, CrSi-rich the relatively Si _- wear coating coated tool, wherein the (N x _B 1 _x) phase is an amorphous phase. 3. The tool according to claim 1, wherein said relatively Si-rich CrSi (N _x B _1-
x ) A tool coated with a wear-resistant coating, wherein the phase has a crystal grain size of 500 nm or less.