JP3392115B2 - Hard coating tool - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated tool used for cutting metal materials and the like, particularly high speed cutting,
The present invention relates to a coated tool applied to dry cutting.

[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, TiAlN coatings represented by JP-A-62-56565 and JP-A-2-194159 have been developed and used as cutting tools. Has been applied. The TiAlN coating is
Since it has better oxidation resistance than TiN and TiCN, it significantly improves the performance of the cutting tool in the cutting of heat-treated steel where the 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. Under such a cutting environment, a chemical reaction occurs between the wear-resistant coating on the surface of the cutting tool and the material to be cut, and the tool life is not limited to the scrape wear of the flank but also the crater of the rake face. The tendency to be strongly controlled by wear has become stronger. Under the severe cutting environment, the conventional TiN, TiCN and TiAlN coatings are accompanied by an increase in crater wear due to a chemical reaction with a workpiece and an increase in abrasive wear under the severe cutting environment. The actual situation is that a sufficient cutting life cannot be obtained due to the generation of thermal cracks due to an increase in cutting heat. Further, when applying a PVD coating in lathe machining, which is relatively continuous cutting, it is extremely important to suppress this crater wear. Therefore, in order to solve these problems, it is necessary to improve the cutting temperature, or to improve the crater wear resistance without softening the coating even if the temperature rises to some extent. is there.

In order to solve such a problem, first, from the viewpoint of suppressing an increase in cutting temperature, it has been proposed to coat a lubricating film. For example, Tokuyohei 11-50277
And molybdenum disulfide disclosed in Japanese Patent Laid-Open No. 7-1.
A hard coating having wear resistance is laminated on the outermost surface of a lubricating coating made of tungsten carbide and diamond-like carbon disclosed in Japanese Patent No. 64211, and the diffusion phenomenon between the coating and the work piece is suppressed based on suppression of a rise in cutting temperature. Cutting tools have been developed, but in any case, since the adhesion to the underlying hard coating is poor and the coating itself is extremely brittle, these lubricating coatings easily peel or break during cutting. No effect has been achieved in the cutting environment. Also, JP-A-11-156992
Although a tool coated with a Cr-based lubricating coating is disclosed in Japanese Patent Laid-Open Publication No. JP-A-2003-242242, the Cr-based coating has low hardness itself and extremely poor wear resistance, and has not yet improved crater wear resistance. From the viewpoint of maintaining the high temperature hardness of the coating and maintaining the crater abrasion resistance at high temperatures, no specific proposal has been made yet. As a comparatively similar case, there is proposed a case where Si or boron is added to a TiAlN-based film as seen in JP-A-7-310171, but oxidation resistance is improved by simple addition, but high temperature The result has not been to increase hardness. In addition, as disclosed in JP-A-10-176259, it has been proposed to add various third components, but none of them improves the high temperature hardness of the coating.

[0005]

In view of these circumstances, the present invention mainly uses TiAl, which is excellent in this property, in order to be able to cope with dry cutting and high speed cutting, that is, not to impair the conventional oxidation resistance. An object of the present invention is to provide a physical vapor deposition hard film coated tool in which the abrasive wear resistance and crater wear resistance of a hard film as a component are remarkably improved.

[0006]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a tool base with a metal element containing Ti, Al, and B as main components, and C,
In a hard coating tool coated with one or more hard layers composed of at least one or more elements selected from N and O, a nitride phase of B is interposed in at least one of the hard layers. A hard film-coated tool characterized by the above.

[0007]

With the TiAlN coating as an example, the inventors of the present invention have earnestly studied the effects of various additive components in the arc ion plating method. As a result, the addition of B (boron) and the optimization of the coating conditions have made the TiAlN anti-abrasive. We have come to the knowledge that the wear resistance and crater wear resistance can be significantly improved.
As a result of diligent investigation of the cause, it was found that these B nitrides were extremely finely dispersed inside the TiAlN film, and
The hardness of AlN coating is Vickers from 2800 to 3300
It was confirmed that it was rising significantly. That is, the surprising fact that a ceramic hard coating can be dispersion strengthened and the method thereof have been discovered.

FIG. 1 shows an ESCA analysis result of a film coated with a TiAlB target at a substrate bias of 350 V, a reaction pressure of 0.5 Pa and 300 ° C. From FIG. 1, it was confirmed from this film that a diffraction peak generated from the binding energy of BN was confirmed, and that the film was composed of a TiAlN phase and a BN phase. Further detailed observation with a transmission electron microscope confirmed that the B nitride layer was a nanocrystal of about 25 nm, and that the nanocrystal was dispersed in a TiAlN layer having a fcc structure and growing in a columnar shape. did. It is considered that the nanocrystals generated lattice strain and significantly increased the hardness of TiAlN by the dispersion strengthening mechanism. As a result, the addition of B greatly improved the film hardness, resulting in a significant improvement in the abrasive wear resistance and the crater wear resistance. As a result of further detailed investigation of other reasons, BN internally diffuses into the coating surface during cutting to reduce the friction coefficient, suppress the rise of cutting temperature, and as a result, improve abrasive wear resistance and crater wear resistance. It became clear that there is.

However, the dispersed nanocrystals are not always formed. The coating condition is a very important factor. When the ion energy at the time of coating is small, for example, when the applied bias voltage is relatively low at 50 V, B replaces the metal atom of TiAlN in the fcc structure to form (TiAlB) N which is a solid solution, and the hardness rises only slightly. Not confirmed. In order to intervene with nanocrystals, it is necessary to form a film with extremely high ion energy. The bias applied to the substrate during coating results in the inclusion of this nanocrystalline phase when coated above 300V. Thus, it is clear that the ion energy at the time of coating influences the crystal morphology, but further research is needed on the reason.

Regarding the coating temperature, when coating is performed at a temperature exceeding 450 ° C., the diffusion energy of B becomes high, and B migrates and diffuses on the surface to form a solid solution in TiAlN to form (TiAlB) N. Therefore, optimization of the bias voltage and coating temperature is needed to interpose the nanocrystals.

The increase in hardness tended to be substantially proportional to the amounts of B and boron added. As the hardness increases, the compressive stress remaining in the coating increases, and the hard layer containing TiAl as the main component and Ti
Since the adhesion between the hard layers containing as a main component tends to deteriorate, the addition amount of B is preferably 30 atomic% with respect to TiAl.
It is considered better to keep below.

Further, in the hard coating containing TiAl as a main component, the preferential orientation of crystal growth affects the cutting performance. When the strongest diffraction peak in X-ray diffraction is (200), although the film hardness is soft, the crystals show clear columnar crystals, resulting in excellent crater abrasion resistance.
On the other hand, when the strongest diffraction peak is (111), the film is not a clear columnar crystal but exhibits a block crystal in which the columnar crystal is divided. In this case, the individual blocks tend to fall off together with the cutting chips during cutting, and the crater wear progresses somewhat faster. Therefore, it is more preferable that the TiAl-based coating be oriented in (200). The orientation depends on the coating conditions, but if the nuclei having the (200) orientation are formed under the optimum conditions at the initial stage of the coating, the coating conditions thereafter are not particularly limited. This is because the film grows epitaxially from this nucleus.

By substituting a part of Ti with another component, it is possible to further improve the wear resistance or the oxidation resistance of the hard layer containing TiAl as the main component. Substitution with components of groups 4, 5 and 6 of the periodic table tends to increase the hardness of the TiAl main component hard layer, and substitution with Y segregates this component at the grain boundaries and suppresses oxygen diffusion at the grain boundaries. However, as a result, the oxidation resistance tends to be improved. If the amount of substitution exceeds 30 atomic%, the crystals will not grow in columns and the toughness of the film will deteriorate, so it should be 30 atomic% or less. In particular,
Even if Si is added, under the same coating conditions, Si ₃ N
It was found that it is possible to interpose ₄ nanocrystals. It is possible to further improve the film hardness by interposing SiN nanocrystals in addition to BN nanocrystals, and further increase the Vickers hardness by 36 depending on the amount of Si added.
A high hardness of 00 to 4200 was possible. Along with the lubricity of BN, the life can be further extended.

As described above, as a result of greatly improving the crater wear resistance, the tool coated with a multilayer hard coating according to the present invention is effective for a tool used for milling cutting, but it is still more conventional than an alumina coating. CVD with
It has become possible to apply it to the lathe processing field where coated tools were used. Since turning is relatively continuous cutting, tool life is often dominated by crater wear. Also in the present invention, if the film thickness is thin, the crater wear resistance will be inferior to the CVD film, but by coating at least 6 microns, it is possible to give crater wear resistance equal to or higher than that of the CVD film. I confirmed that there is. Further, in terms of the fracture resistance of the tool, the present invention is based on the PVD method. As compared with a CVD-coated tool in which a compressive stress remains in the coating, cracks are less likely to occur, and a residual tensile stress is present in the coating. As a result, the chipping resistance was over 10 times overwhelmingly excellent.

Further, when the PVD-coated tool of the present invention is applied to turning, if the surface of the cemented carbide substrate, which is a substrate, is polished, microcracks due to polishing may be present internally on the insert surface. In some cases, this microcrack may be the starting point and film peeling may occur. Therefore, the surface is not polished by a diamond grindstone, CNMG, D in ISO classification
When NMG, VNMG, SNMG, and TNMG type inserts are used, it is possible to achieve better film adhesion and a longer life.

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. The arc discharge type ion plating physical vapor deposition method is desirable. Hereinafter, the present invention will be described based on examples.

[0017]

EXAMPLES Example 1 Using an arc ion plating apparatus, various alloy targets that are evaporation sources of metal components, and reaction gases such as nitrogen gas, oxygen gas, and methane gas that can obtain a target film can be obtained. Under the conditions of the coated substrate temperature of 350 ° C., the reaction gas pressure of 0.5 Pa, and the substrate applying bias voltage of 320 V, the coated substrate is a cemented carbide 6-blade end mill with an outer diameter of 10 mm, and a carbide insert for milling. Various A layers shown in Table 1 were coated.

[0018]

[Table 1]

The B layer was coated at a coating temperature of 450 ° C., a substrate applied bias of 70 V, and a reaction gas pressure of 1.0 Pa to prepare an example of the present invention. In the comparative examples, the TiAl-based films described for convenience in the A layer and B layer columns and other films were also coated under the same conditions as the B layer in the present invention example. Total thickness of film is 4
was set to μ. B was contained in the film by adding a necessary amount to the TiAl target. The cemented carbide used for the end mill is a fine grained cemented carbide with 7 wt% Co and a WC average particle size of 0.9 micron. The cemented carbide used for the insert is JIS-P20 grade cemented carbide. The film thickness of the hard film was unified to a total thickness of 3.5μ.

A cutting test was conducted using the obtained hard film-coated end mill. Under this cutting condition, the tool life is dominated by defects caused by the generation of thermal cracks due to the increase in cutting heat due to the progress of crater wear or abrasive wear. Therefore, the tool life was taken as the cutting length when the tool became uncut. The cutting specifications are shown below.

The cutting conditions for the 6-flute carbide end mill are as follows: side surface cutting down cut, work material SKD11 (hardness HRC6
5), cut Ad 10 mm × Rd 0.1 mm, cutting speed 200 m / min, feed 0.03 mm / blade, air blow used. When it becomes impossible to cut, it is judged as the life, and the results are also shown in Table 1.

The insert cutting conditions are the tool shape SEE4.
2 TN, the work material is chamfered with a width of 100 mm and a length of 250 mm, and the work material SKD61 (hardness HRC45), cut depth of 1.5 mm, cutting speed of 350 m / min, feed of 0.
15 mm / blade, dry cutting. Also in this case, the crater wear controls the tool life, and the chips are damaged due to the progress of the crater wear, or the cutting temperature rises due to the progress of the abrasive wear and thermal cracks are generated, and the chips are damaged. Table 1 also shows the cutting length leading to the chipping.

As is clear from Table 1, the examples of the present invention show remarkable improvement in life. Inventive Examples 1 to 5 are examples of single-layer coatings in which nanocrystals are interposed in various compositions, Inventive Example 5
Is an example in which the crystal orientation is (111). The cutting life tended to be slightly shorter than that of the (200) orientation. Inventive Examples 6 and 7 are a layer in which nanocrystals are interposed and TiA.
This is an example of a multilayer of 1N-based coating, and it was recognized that the cutting life was slightly improved by using a multilayer. Inventive Examples 9 to 11 are examples in which C and O are added to nitrogen using a gas containing oxygen and carbon, and a slight improvement in cutting life was confirmed here. Since all of these comparative examples had a short life,
It was confirmed that it was largely due to the improvement of the abrasive wear resistance and the crater wear resistance. Comparative Examples 12 to 15
Is an example of a film having a known composition, Comparative Examples 16 to 19 are examples of a known multilayer film, and Comparative Examples 20 and 21 contain B,
This is an example of a solid solution (TiAlB) N film with different coating conditions and no intervening nanocrystals. In all cases, the cutting life is not satisfactory.

Example 2 An example of the present invention was prepared under the same conditions as in Example 1 using a target in which a part of Ti of the TiAlB metal target was replaced with another component. The same cutting evaluation as in Example 1 was performed, and the results are also shown in Table 2.

[0025]

[Table 2]

As is clear from the results in Table 2, TiAl
The life can be further improved by adding the fourth component to the B-based hard coating. In each of the examples of the present invention, Ti
This is an example in which the fourth component is added to the AlBN system and the amount of B constituting the nanocrystal is unified to 5 at%. Even when the B content is other than 5 at%, the same tendency as in Example 1 is exhibited.

Example 3 Cutting evaluation was performed on each sample by turning. Carbide insert for turning is JI
S-M20 grade was used. The insert used was an embossed CNMG432 type (indicated as embossed in Table 3).
And a similar shape with an R breaker using a grindstone (Table 3
Displayed as medium and R processing. ). First, inventive examples 34 to 47 and comparative examples 48 to 53 were manufactured by the same method as that shown in Examples 1 and 2. Next, by well-known CVD coating, TiCl ₄ , AlCl ₃ , C
Using O ₂ , H ₂ and N ₂ gas, 800 ° C. to 1000 ° C.
Comparative Examples 54 to 57 were prepared according to the reaction temperature of.

The wear resistance was evaluated by using S53C (H
B220), and the cutting condition is a cutting speed of 200 m / mi.
n, cut 2 mm, feed per blade 0.3 mm / r
ev and dry type. Under this cutting condition, the crater wears out and reaches the end of its life. Table 3 also shows the cutting time until chipping. The fracture resistance was evaluated by using S53C having four grooves, cutting conditions of 100 m / min, incision of 2 mm, feed per blade of 0.4 mm / rev, and the number of impacts before fracture. Defects are caused by repeated impacts on the coating during cutting, resulting in frequent occurrence of fine cracks in the coating.
It was generated by the propagation of these cracks to the base material. The results are also shown in Table 3.

[0029]

[Table 3]

In all the examples of the present invention, the life in continuous longitudinal cutting is equal to or more than that of the CVD film of the comparative example, and the fracture resistance is overwhelmingly excellent. Therefore, the present invention has a particularly remarkable effect on high-speed cutting and dry high-speed cutting in turning. It was also confirmed that the fracture resistance was improved by forming a multilayer with a soft film without intervening nanocrystals. As compared with the PVD examples of Comparative Examples 48 to 53, the invention examples 34 to 47 resulted in a slower rate of progress of crater wear during cutting, resulting in a significant improvement in tool life. Comparative Examples 48 to 50 are ordinary PVD coatings, which have a thin film thickness and have an extremely short life in continuous cutting. In Comparative Examples 51 and 52, the film thickness was set thicker to 10 μ, but the crater wear progressed rapidly and the life was short. In Comparative Example 53, B was added, but no nanocrystal was interposed, and a satisfactory life was not achieved. Further, in the well-known CVD examples of Comparative Examples 54 to 57, although the crater wear is excellent and the life is relatively long in continuous cutting, the tensile stress remains in the coating, resulting in a markedly poor fracture resistance.

Example 4 Various coatings shown in Table 4 were coated on the cemented carbide under the same conditions as in Example 1. In order to avoid the influence of the base, the film thickness was set to 10 μm, a scratch test was performed in an Ar atmosphere at 700 ° C., the depth of the indentation scratch at a load of 50 N was compared, and the hardness of the film at 700 ° C. was examined. . The results are also shown in Table 4.

[0032]

[Table 4]

Although it is technically impossible to directly measure the high temperature hardness of the coating film because of problems in the apparatus at present,
It is considered that the scratch depth at high temperature in the scratch test correlates with the high temperature altitude. Comparative Examples 67 to 70, which are well-known films, and TiAlB without intervening nanocrystals
In the N film, the high temperature hardness is soft in Comparative Examples 71 and 72,
The depth of the scratch became 700 microns or more. Invention Example 5
The depth of the scratches is 1 in the film in which 8 to 66 nanocrystals intervene.
It becomes 0 to 160 microns, which suggests that the high temperature hardness is extremely high. In particular, it is considered that 64, 65 and 66 in which nanocrystals of both BN and SiN are interposed have extremely high high temperature hardness.

[0034]

INDUSTRIAL APPLICABILITY As described above, the hard film-coated tool of the present invention is superior in crater wear resistance to the conventional PVD-coated tool, has a remarkably long tool life in dry high-speed cutting, and is produced in cutting. It is extremely effective in improving the productivity, reducing the cost, and improving the environment.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an ESCA analysis result of a hard layer of an example of the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-10-140330 (JP, A) JP-A-10-176288 (JP, A) JP-A-7-310171 (JP, A) JP-A-2002-18606 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B23B 27/14 C23C 14/06

Claims (5)

(57) [Claims] 1. A hard-coated tool in which a tool base is coated with one or more hard layers composed of a metal element consisting of Ti, Al and B and at least one element selected from C, N and O. 2. A hard film-coated tool characterized in that a nitride phase of B is interposed in the hard layer. 2. The hard coating tool according to claim 1, wherein the hard layer has a strongest peak surface index in X-ray diffraction of (200). 3. The hard coating tool according to claim 1, wherein a part of Ti in the hard layer is excluded from Ti within a range of 30 atomic% or less. element,
A hard film-coated tool characterized by being replaced with one or more elements of Si and Y. 4. A hard coating tool according to claim 3, wherein a B nitride phase and a Si nitride phase are interposed in the hard layer. 5. The hard coating tool according to any one of claims 1 to 4, wherein the tool base is a carbide insert for turning, and the coating has a total thickness of 6 μm or more on the rake face. Hard coating tool