JP3481216B2 - Wear-resistant film-coated 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 hard coating tool used for high speed cutting of high hardness steel.

[0002]

2. Description of the Related Art In the direct cutting of heat-treated steel for the purpose of improving the efficiency of metal working, JP-A-62-56565,
TiAlN typified by JP-A-2-194159
A coating has been developed and applied to cutting tools. TiAlN
Since the coating has better oxidation resistance than TiN and TiCN, it significantly improves the performance of the cutting tool in the cutting of heat-treated steel whose cutting edge reaches a high temperature.

However, in recent years, in order to meet the demands for higher efficiency and higher accuracy of machining, dry machining is regarded as important in view of environmental problems and machining cost reduction in addition to high cutting speed. There is. In such a cutting environment, the welding phenomenon between the wear-resistant film coated on the surface of the cutting tool and the material to be cut (hereinafter referred to as the work material) has a great influence on the cutting performance and the cutting temperature. However, even with a TiAlN-based coating, the oxidation resistance is not sufficient. That is, the conventional TiN and TiCN
In such a severe cutting environment, the TiAlN coating cannot obtain sufficient cutting performance due to the increase in frictional resistance due to the welding phenomenon with the work material and the progress of oxidation, and the progress of wear due to oxidation. The current situation is that we have not been able to sufficiently suppress this.

In order to solve such a problem, from the viewpoint of improving the welding resistance, molybdenum disulfide disclosed in Japanese Patent Publication No. 11-502775 and JP-A No. 7-164211 are disclosed.
Although a cutting tool has been developed in which a lubricative coating consisting of tungsten carbide and diamond-like carbon is laminated on the outermost surface of the hard coating as disclosed in Japanese Patent Publication, the adhesion to the hard coating is poor and the coating itself is very brittle. It is poor in oxidation resistance and cannot be sufficiently dealt with under the above cutting environment due to peeling or destruction during cutting, oxidative abrasion and the like.

From the viewpoint of improving the oxidation resistance, there are cases in which a third component is added to TiAlN as typified by JP-A-7-237010 and JP-A-10-130620, but the third component is used. It is the actual situation that the satisfactory improvement of the oxidation resistance is not realized only by the addition of. Further, in Japanese Patent Application Laid-Open No. 8-118106, T
Although a case of iSiN has been proposed, it is simply TiSiN
Has not yet improved the oxidation resistance.

Also, see Japanese Patent Laid-Open No. 11-138038.
Inside the hard coating_ThreeN _FourIntervening grains
There are some cases of Si_ThreeN_FourOxidation progresses through grain boundaries
Therefore, sufficient oxidation resistance has not been imparted yet.

[0007]

In view of the above circumstances, the present invention provides a hard layer which is capable of coping with dry machining and high speed machining, that is, having a high oxidation resistance and a low weldability to a work material. It is an object of the present invention to provide a wear-resistant film-coated tool that has been proposed and is capable of simultaneously achieving oxidation resistance and welding resistance and capable of high-speed dry cutting of high-hardness steel.

[0008]

Means for Solving the Problems The present inventor has made a detailed study on the wear resistance of hard coatings and their effects on various work materials and reduction of frictional resistance, and the layer structure of coatings.
Addition of welding resistance (Cr _a Si ₁ - _a ) (N _x B _1-
x ), where 0.5 ≦ a <1.0, 0.5 ≦ x ≦ 1.0
By improving the welding resistance by coating the A layer having the chemical composition shown in, and further controlling the crystal morphology thereof, it is possible to obtain a hard coating tool having both oxidation resistance and wear resistance. As a result, they have found that the performance of the cutting tool is extremely good in the dry high-speed cutting of high hardness steel, and have reached the present invention. In addition, the A layer is a general TiA
By combining with an IN hard coating or the like, a coated tool with more excellent adhesion is realized. Further, it is desirable that the abrasion resistant film is coated by a physical vapor deposition method.

[0009]

First, the operation of each component of the layer A will be described in detail. CrN is originally known as a film having lubricity, and its friction coefficient is around 0.6.
(Cr _a Si ₁ - _a ) (N _x B _{1 -x} ), provided that 0.5
A nitride or boride nitride composed of Cr and Si having a chemical composition represented by ≦ a <1.0 and 0.5 ≦ x ≦ 1.0 has a coefficient of friction with steel at room temperature in the atmosphere. Compared with 0.8 of the conventional TiAl nitride film and 0.6 of CrN,
Although it shows a low friction of 0.4, the value further decreases to around 0.2 especially at high temperatures. This is S in the film at high temperature
It was confirmed that i was caused by the internal diffusion of i on the surface of the coating due to the reaction with the chips and the formation of a low-melting point Si oxide on the surface of the coating.

With this low melting point Si oxide (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 Was confirmed to have Further, it was clarified that the addition of boron forms BN phase inside the film, and the lubricity of the BN phase further improves the lubricity.

As a result of intensive studies made by the present inventors to improve the oxidation resistance, (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 provide the oxidation resistance superior to that of the (TiAl) N-based coating, which is generally said to have excellent oxidation resistance. It came to the surprising finding that. _{(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 The form is such that particles intervene. When the ion energy is high, the state is almost amorphous as a whole, and the state where the bond between Si and N is confirmed in CrNB is obtained. Completely amorphous CrS when the ion energy is medium and the coating temperature is 550 ° C or higher
The iBN phase exists in the form of fine crystals, and S of this CrSiBN phase
The i content is the Si of the CrSiBN phase that becomes the matrix.
It was confirmed that the form became richer than the amount. It was confirmed that when the temperature was low, it exhibited the same crystal morphology as when the ion energy was high. The reason for the correlation between temperature, ion energy and crystal morphology needs further physical research.

[0012] Above all, when the completely amorphous CrSiBN phase is present as fine crystals, the crystal grain boundaries become very aligned grain boundaries, there are few defects, the diffusion of oxygen at the grain boundaries is remarkably suppressed, and very excellent oxidation resistance. It was confirmed to have. At the same time, by interposing fine crystals, the lattice strain of the matrix is strengthened, the hardness is improved, and the wear resistance is also improved. Furthermore, 1 to 5 nm of Cr on the outermost surface
As a result, a stable oxide layer was formed, resulting in further excellent oxidation resistance.

As coating conditions, the ion energy is relatively medium, a load bias of -100 V to -150 V, a reaction pressure of 1 Pa to 5 Pa, and a coating temperature of 550.
C. or higher is a preferable range.

[0014] The composition of the metal elements A layer constituting the hard coating of the present _{invention, (Cr a Si 1 - a} ) in the value of a is be satisfied 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 and the toughness of the coating itself deteriorates, and internal fracture of the coating and peeling of the coating due to the fracture become noticeable in dry high speed cutting, resulting in sufficient performance. Can't exert.

[0015] In the case of nitrides or窒硼product according to the A _layer, N x _{B 1} - and must be able to satisfy 0.5 ≦ x ≦ 1.0 in _x, the value of x is 0. If less than 5,
The hardness of the coating increases significantly, the residual compressive stress increases, and the adhesion of the coating deteriorates, resulting in insufficient cutting performance.

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 coating is reduced. Therefore, it is more preferably 500 nm or less. Although the layer A has excellent adhesion, low friction and high oxidation resistance under static and dynamic conditions,
In high-speed dry cutting of high hardness steel having an HRC of more than 60, adhesion may not be sufficient with a single coating and peeling may occur. Therefore, stacking with a (TiAl) N layer or the like having excellent adhesion resistance and wear resistance is a more preferable result in such high hardness steel cutting.

It goes without saying that the (TiAl) N layer used here is expected to have the same function even if the third metal component is added in some cases.

The coating method of the hard coating tool of the present invention is not particularly limited, but in consideration of the thermal influence on the coating base material, the fatigue strength of the tool, the adhesion of the coating, etc., Arc discharge type 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 such as sputtering in which a bias voltage is applied to the coated substrate side is desirable.

[0019]

EXAMPLES The present invention will be described below based on examples. A
Evaporation of metal components using the Quark ion plating device
The target made of various alloys and the reaction gas
N _TwoSelect the gas that gives the desired film and select
Conditions for covering substrate temperature 600 ° C. and reaction gas pressure 3.0 Pa
, 2 blades made of cemented carbide with an outer diameter of 10 mm, which is a coated substrate
-130V for end mills and cemented carbide inserts
Voltage is applied so that the total thickness of all coatings is 3 μm.
Filmed Also, boron and Si are essential for the target that is the evaporation source.
The required amount was added. Prototypes of the present invention and comparative examples are shown in Table 1.
Show. In the case of multiple layers, the total thickness of layer A is 1.5μ and the total thickness of other layers.
It was evenly coated to a thickness of 1.5μ.

[0020]

[Table 1]

A cutting test was conducted using the obtained hard film-coated end mill and hard film-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. The obtained results are also shown in Table 1. The cutting specifications are shown below.

The cutting conditions for the 2-flute carbide end mill are as follows: side surface cutting down cut, work material S50C (hardness HB22
0), cut Ad 10 mm x Rd 1 mm, cutting speed 2
50 m / min, feed 0.06 mm / tooth, air blow used.

The insert cutting conditions are the tool shape SEE4.
2TN, chamfering of width 100mm x length 250mm,
Work Material SKD61 (Hardness HRC45), Notch 2.0
mm, cutting speed 150 m / min, feed 0.15 mm /
Rev and dry cutting. The test results are also shown in Table 1.

Oxidation resistance is 9 μm by coating a film of 5 μm each.
It was evaluated by the thickness of the oxide layer formed when it was held in the atmosphere at 00 ° C. for 1 hour. Friction coefficient is SKD6 at 600 ℃
The ball No. 1 was used and the measurement was performed by a general ball-on-disk method. The results are shown in Table 2.

[0025]

[Table 2]

Comparative Examples 16 and 17 are comparative examples in the case where the amount of Si or boron is too large, and the results show that the static evaluation values are satisfied but the adhesion is insufficient and the tool life is short. 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 inventive examples.

On the other hand, the examples of the present invention are excellent in static evaluation characteristics and at the same time are excellent in adhesiveness, and the abnormal wear due to the welding phenomenon, the oxidative wear of the coating, and the peeling of the coating do not proceed, and the results are comprehensive. Tool life is significantly improved. Therefore, the present invention is sufficiently applicable to dry high speed cutting of high hardness steel.

[0028]

As described above, the hard coating tool of the present invention has excellent adhesion, low friction and high oxidation resistance at the same time as compared with the conventional coated tool, so that it is remarkably effective in dry high speed cutting. It has a very long tool life and is extremely effective in improving productivity in cutting.

[Brief description of drawings]

FIG. 1 is a schematic diagram of (Cr _a Si _1-a ) (N of the present invention.
_x B _1-x) fine amorphous crystals interposed in the matrix _{(Cr a Si 1-a)} TEM of (N _{x B 1-x)}
Show the image.

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

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

Claims (4)

(57) [Claims] 1. A hard film, (Cr_aSi
₁−_a) (N_xB₁−_x), Where 0.5 ≦ a <1,
A layer having a chemical composition represented by 0.5 ≦ x ≦ 1
In a wear-resistant coating tool coated with at least one layer,
The A layer is CrSi (N_xB₁−_x)
Phase and CrSi (N_xB₁− _x)
Wear-resistant film coating characterized by being composed of
Ingredient 2. The wear resistant film coated tool according to claim 1, wherein the relatively Si-rich CrSi (N _x B _{1 -x} ) phase is an amorphous phase. 3. The wear resistant film coated tool according to claim 1, wherein the relatively Si-rich CrSi (N _x B _1-
x ) A crystal grain size of the phase is 500 nm or less, an abrasion resistant coating tool. 4. A tool coated with an abrasion resistant film according to claim 1, wherein the A layer and a nitride containing Ti and Al as main components,
A wear-resistant film-coated tool characterized in that two or more layers of carbonitride, oxynitride, and oxyboride are laminated.