JP2002096205A - Hard film covering tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a physically deposited hard film covering tool capable of corresponding to drying and accelerating high hard steel cutting work after thermal treatment and restraining deterioration of film hardness even under high temperature. SOLUTION: The hard film covering tool to cover at least one layer of hard layers constituted of a metal element made of Ti, Al and Si and at least one kind of elements selected from B, C, N and O on a tool base body is constituted by interposing a nitride phase of Si in the hard layer.

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, and more particularly to a hard film coated tool applied to high speed cutting and dry cutting of high hardness steel after heat treatment. is there.

[0002]

2. Description of the Related Art In the direct cutting of tempered steel for the purpose of improving the efficiency of metal working, a TiAlN film typified by JP-A-62-56565 and JP-A-2-194159 has been developed and used as a cutting tool. Have been applied. TiAlN film is
Since the oxidation resistance is superior to TiN and TiCN, the performance of the cutting tool is remarkably improved in the cutting of tempered steel whose cutting edge reaches a high temperature.

However, in recent years, in order to reduce the processing cost, it has been a general practice to perform rough processing before heat treatment and finish processing after heat treatment. It is getting stronger. Furthermore, in order to increase the efficiency and precision of cutting of these hardened materials after heat treatment, dry cutting is increasingly regarded as important from the viewpoint of high cutting speed, environmental issues and reduction of processing costs. It is in. In such a cutting environment, the chips become red-hot from the beginning of cutting, so that not only the oxidizing property of the film but also the high-temperature hardness of the film is very important. In other words, a film having a large degree of softening at a high temperature results in markedly deteriorated wear resistance.

At present, no specific proposal has been made yet to solve such a problem. However, as a comparatively similar example, as disclosed in Japanese Patent Application Laid-Open No. Hei 7-310171, a TiAlN-based Although it has been proposed to simply add Si to the film to improve oxidation resistance, simple addition results in deterioration of the high-temperature hardness of the film, resulting in satisfactory results in terms of wear resistance. Absent. Other JP-A-10-176
As disclosed in Japanese Patent No. 259, there is a proposal to add a third component to a TiAlN system, but at present it has not been improved in high-temperature hardness.

[0005]

SUMMARY OF THE INVENTION In view of these circumstances, the present invention provides a physical vapor deposition capable of coping with the dry and high-speed cutting of high-hardness steel after heat treatment and suppressing the deterioration of film hardness even at high temperatures. It is an object to provide a hard film-coated tool.

[0006]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a tool base comprising a metal element composed of Ti, Al, Si, B, C,
A hard-film-coated tool comprising at least one hard layer composed of at least one element selected from N and O, wherein a Si nitride phase is interposed in the hard layer. It is a hard film coated tool.

[0007]

The present inventors have conducted intensive studies on the effects of various additives using the example of a TiAlN film. As a result, by adding Si and optimizing the coating conditions, the life of dry high-speed cutting of a hard material can be greatly improved. I got the knowledge. Unlike the simple addition of Si, these Si nitrides were dispersed very finely inside the TiAlN film, and the room temperature hardness of the TiAlN film was significantly increased from 2800 to 3500 in Vickers hardness. That is, the present inventors have discovered the surprising fact that a ceramic hard coating can be dispersed and strengthened, and a method thereof. Incidentally, the hardness at high temperature tends to substantially depend on the room temperature hardness.

FIG. 1 shows an ESCA analysis result of a film coated with a substrate bias of 300 V and a reaction pressure of 0.5 Pa at 300 ° C. using a TiAlSi target. From FIG. 1, a diffraction peak generated from the binding energy of Si ₃ N ₄ was confirmed from this film, and the film was composed of a TiAlN phase and Si ₃ N ₄
It was confirmed that it was composed of phases. Further observation by a transmission electron microscope showed that the Si nitride layer was a nanocrystal of about 40 nm, and that the nanocrystal was dispersed in a TiAlN layer having a fcc structure and growing in a columnar shape. . It is considered that the nanocrystals generated lattice strain and greatly increased the hardness of TiAlN by the dispersion strengthening mechanism. As a result, the hardness of the film was significantly improved by the addition of Si. Further detailed investigations have revealed that during cutting, Si diffuses internally into the film surface to form Si oxides, which reduce the coefficient of friction and suppress the rise in cutting temperature. .

However, the dispersed nanocrystals are not always formed. The coating conditions are 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, Si replaces the metal atoms of TiAlN in the fcc structure to form TiAlSiN which is a solid solution, and a slight increase in hardness is confirmed. Was. 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 at 250 V or higher. Thus, it is clear that the ion energy at the time of coating affects the crystal morphology, but further study is required for the reason.

With respect to the coating temperature, if the coating is performed at a temperature exceeding 450 ° C., the diffusion energy of Si increases, and the Si migrates and diffuses on the surface to form a solid solution with TiAlN to form TiAlSiN. Therefore, it is possible to interpose nanocrystals by optimizing the bias voltage and the coating temperature.

The increase in hardness tended to be substantially proportional to the amount of Si added. As the hardness increases, the compressive stress remaining in the coating increases, and the adhesion of the hard layer mainly composed of TiAl tends to deteriorate. Therefore, the amount of Si added is preferably suppressed to 50 atomic% or less based on TiAl. It is considered better.

Further, in a hard coating mainly composed of TiAl, 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 exhibit clear columnar crystals, resulting in excellent crater wear resistance.
On the other hand, when the strongest diffraction peak is (111), the film does not become a clear columnar crystal but shows a block-like crystal in which the columnar crystal is divided. In this case, the individual blocks tend to fall off together with the chips during cutting, and the wear progresses somewhat faster. Therefore, it is better that the TiAl-based film is oriented to (200).
More preferred. Although the orientation depends on the coating conditions, the coating conditions after that are not particularly limited as long as nuclei having the (200) orientation are formed under optimum conditions in the initial stage of coating. 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 oxidation resistance of the hard layer mainly composed of TiAl. 4,
Substitution with a group 5 or 6 component tends to increase the hardness of the TiAl main component hard layer to some extent. Substitution with Y causes this component to segregate at the grain boundaries and suppress oxygen diffusion at the grain boundaries. It tends to improve oxidation resistance. If the substitution amount exceeds 30 atomic%, the crystal does not grow in a columnar shape, and the toughness of the film deteriorates.

As described above, as a result of significantly improving the film hardness at high temperatures, the hard film-coated tool according to the present invention is effective for tools used for milling cutting. It is also applicable to the lathe processing field where a CVD coated tool having a coating is used. Since the turning process is a relatively continuous cutting process, the cutting temperature tends to be particularly high, and the conventional PVD film cannot achieve satisfactory wear resistance with respect to the CVD film. Also in the present invention, when the film thickness is small, the crater abrasion resistance is inferior to the CVD film, but by coating the film of the present invention at least 6 microns, the abrasion resistance equal to or more than that of the CVD film is provided. Confirmed that it is possible. Further, with respect to the fracture resistance of the tool, the present invention is based on the PVD method, and the coating has a residual compressive stress in the coating, less cracks, and a CVD coated tool in which the coating has a tensile residual stress. The result was over 10 times the overwhelmingly excellent fracture resistance.

When the PVD-coated tool of the present invention is applied to turning, if the surface of the cemented carbide insert as a substrate is polished, micro-cracks due to polishing may be present inside the insert surface, and the PVD coating may be formed. In some cases, the microcracks serve as starting points to cause film peeling. Therefore, the surface is not polished with a diamond grindstone.
The use of NMG, VNMG, SNMG, and TNMG type inserts enables more excellent film adhesion and longer life.

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. It is desirable to use an arc discharge type ion plating physical vapor deposition method.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. (Example 1) Using an arc ion plating apparatus,
A target made of various alloys, which is a source of evaporation of metal components, and a target gas obtained from a reaction gas of nitrogen gas, oxygen gas, or methane gas are selected.
Under the conditions of 0 ° C., a reaction gas pressure of 1.0 Pa, and a substrate application bias voltage of 280 V, the A-layer shown in Table 1 on a 6-blade end mill made of cemented carbide having a diameter of 10 mm, which is a coated substrate, and a milling insert. Was coated.

[0018]

[Table 1]

The layer B was coated at a coating temperature of 450 ° C., a substrate application bias of 70 V, and a reaction gas pressure of 1.0 Pa to prepare an example of the present invention. In the comparative example, the TiAl-based and other films described for convenience in the A layer and B layer columns were also coated under the same conditions as the B layer in the present invention. The total thickness of the film is 4
μm. Si was added to 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 having 7 wt% Co and an average WC particle size of 0.9 μm. The cemented carbide used for the insert is JIS-P20 grade cemented carbide. The thickness of the hard coating was unified to a total thickness of 3.5 μm.

A cutting test was performed using the obtained hard film-coated end mill. The tool life is governed by the progress of crater wear or abrasive wear under these cutting conditions. The cutting length when the tool could not be cut was set as the cutting length.
The cutting specifications are shown below.

The cutting conditions of the 6-flute carbide end mill are side cutting down cut, work material SKD11 (hardness HRC6).
5), incision Ad10 mm × Rd0.1 mm, cutting speed 200 m / min, feed 0.03 mm / blade, and use of air blow. The time when cutting became impossible was determined as the life, and the results are also shown in Table 1.

The insert cutting conditions are as follows: Tool shape SEE4
2TN, 100mm width x 250mm length chamfering,
Work material SKD61 (hardness HRC45), cut 1.5
mm, cutting speed 350m / min, feed 0.25mm /
Blade, dry cutting. In this case as well, the cutting temperature becomes high, and the wear of the coating governs the tool life and the chip is broken due to the progress of the wear, or the cutting temperature rises and a thermal crack is generated and thereby broken. Table 1 also shows the cutting length leading to chipping.

As is evident from Table 1, the example of the present invention shows a remarkable improvement in life. Since all of the comparative examples had short lifespans, it was confirmed that these were largely due to improvements in abrasive wear resistance and crater wear resistance. Examples 1 to 5 of the present invention are examples of a single layer film in which nanocrystals are interposed in various compositions.
This is an example of 1). The cutting life tended to be slightly shorter than the (200) orientation. Examples 6 and 7 of the present invention are examples of a multilayer of a layer having nanocrystals and a TiAlN-based film,
A slight improvement in the cutting life was observed with the multilayer structure. In Examples 9 to 11 of the present invention, nitrogen was used as a main component, and the respective components were added using B, C, O gas and the like. Comparative Examples 12 to 15 are examples of known coatings, Comparative Examples 16 to 19 are examples of known multilayers,
0 and 21 contain Si, but the coating conditions are different,
It is an example of a solid solution TiAlSiN coating with no intervening nanocrystals. In any case, the cutting life is not satisfactory.

(Example 2) An example of the present invention was prepared under the same conditions as in Example 1 by using a target in which part of Ti of a TiAlSi 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 Si-based hard coating. In each of the examples of the present invention, T
This is an example of the case where the amount of Si constituting the nanocrystal is made to be 5 at% by adding the fourth component to the iAlSiN system. Even when the Si content is other than 5 at%, the same tendency as in Example 1 is exhibited.

(Embodiment 3) Next, JI
Using S-M20 grade equivalent, insert is embossed C
NMG432 type (shown as embossing in Table 3) and similar shape (R in Table 3
Processing and display. ) And were used. Examples 1 and 2
Example 34 of the present invention
To 47 and Comparative Examples 48 to 53 were produced. As a comparative example, TiCl ₄ ,
Using AlCl ₃ , CO ₂ , H ₂ , N ₂ gas, 800
Comparative Examples 54 to 57 were prepared at a reaction temperature of from 1000C to 1000C. The cutting performance of each sample was evaluated by lathing. The cutting conditions are shown below.

The wear resistance was evaluated using S53C (H
B220), and the cutting conditions were a cutting speed of 200 m / mi.
n, notch 2mm, feed 0.3mm / r per blade
ev, dry type. Under these cutting conditions, the cutting is continuous cutting in the longitudinal direction, the cutting temperature rises, and the crater wears out and the life ends, causing chipping. Table 3 also shows the cutting time until chipping. The fracture resistance was evaluated using S53C having four grooves, cutting conditions were 100 m / min, cutting depth 2 mm, feed per blade 0.4 mm / rev, and the number of impacts before fracture. As a result of the repeated impact of cutting on the coating, fine cracks frequently occurred in the coating, and the cracks were generated by the propagation of the cracks to the base material. The results are also shown in Table 3.

[0029]

[Table 3]

In contrast to the PVD comparative example, the example of the present invention has a lower rate of progress of crater wear during cutting, resulting in a remarkable overall improvement in tool life. In each of the examples of the present invention, the life in the longitudinal continuous cutting of the turning is not less than that of the CVD coating, 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. In addition, it was confirmed that a multilayer having a soft coating without intervening nanocrystals had a tendency to improve fracture resistance. Comparative Examples 48 to 50 are well-known PVD coatings, and have a very small thickness and an extremely short life in continuous cutting. Comparative Examples 51 and 5
In No. 2, the film thickness was set to 10 μm, but the crater wear progressed quickly and the life was short. In Comparative Example 53, Si was added, but no nanocrystal was interposed, and a satisfactory life was not achieved. Comparative Example 5
The known CVD coatings Nos. 4 to 57 have a relatively long life in continuous cutting because of their excellent crater wear resistance, but the result is that the tensile stress remains in the coating, so that the fracture resistance is extremely poor.

Example 4 Various coatings shown in Table 4 were prototyped under the same conditions as in Example 1. The thickness of the film was set to 10 μm in order to avoid the influence of the substrate when measuring the hardness. 700 ° C Ar
A scratch test was performed in an atmosphere, and the depth of the indentation scratch when the scratch load was 50 N was measured. The results are also shown in Table 4.

[0032]

[Table 4]

At present, it is technically impossible to directly measure the high-temperature hardness because of a problem in the apparatus, but from Table 4, the scratch depth at high temperature in the scratch test indicates the high-temperature altitude of the film. It is considered to have a correlation with The depths of the scratches of the inventive examples 58 to 63 are 100 to 130 μm, whereas the TiAlSiN coatings without the nanocrystals of the comparative examples 68 and 69 have the depths of 850 and 79.
As a result, the coating of the present invention is extremely excellent in high-temperature hardness. Further, in Comparative Examples 64 to 67, which are well-known films, the film is more deeply scratched.

[0034]

As described above, the hard-coated tool of the present invention has a significantly higher coating hardness than conventional PVD-coated tools, has excellent crater resistance and abrasive wear resistance, and is capable of dry high-speed cutting of high-hardness steel. A remarkably long tool life is obtained in machining, and it is extremely effective in improving productivity, reducing costs, and improving the environment in cutting.

[Brief description of the drawings]

FIG. 1 is a view showing an example of an ESCA analysis result of a hard layer according to an embodiment of the present invention.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3C046 FF02 FF10 FF11 FF13 FF17 FF19 FF25 4K029 BA43 BA44 BA46 BA48 BA53 BA55 BA56 BA58 BA59 BA60 BA64 BB07 BD05 CA04 DD06

Claims (4)

[Claims] 1. A hard material in which a tool base is coated with at least one hard layer composed of a metal element composed of Ti, Al, and Si and at least one element selected from B, C, N, and O. A hard-coated tool, characterized in that a Si nitride phase is interposed in the hard layer. 2. The hard-coated tool according to claim 1, wherein the hard coating layer has a strongest peak plane index in X-ray diffraction of (200). 3. The hard-coated tool according to claim 1 or 2, wherein a part of Ti in the hard-coated layer is an element belonging to Group 4, 5, or 6 of the periodic table, excluding Ti within a range of 30 atomic% or less. A hard film-coated tool, wherein the tool is substituted with one or more elements of Y. 4. A hard-coated tool according to claim 1, wherein the tool base is a turning insert, and the total thickness of the coating is at least 6 μm on the rake face. Coating tool