JPH10140330A - Coated hard alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remarkably improve the adhesion of a film by interposing a relatively soft coating film under the film having high compressive stress such as TiAlN film and absorbing and relaxing the high compressive stress of the film contg. Al. SOLUTION: This coated hard alloy is coated with an external layer composed of one or more kinds among the nitrides, carbon nitrides, carbon-nitrogen oxides, nitrogen borides and carbon-nitrogen borides of Ti and Al in which the atomic ratio of Ti/Al is regulated to (75/25) to (25/75). In this case, as an adhesion improving layer for the external layer, an internal layer of at least one kind selected from the nitrides, carbon nitrides, nitrogen borides and carbon- nitrogen borides of Ti and Al in which the atomic ratio of Ti/Al is regulated to (98/2) to (75/25) is interposed between the external layer and the substrate hard alloy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The results relate to coated hard alloys with excellent wear resistance.

[0002]

2. Description of the Related Art Conventionally, films of TiN, TiCN, etc. have been used widely and generally. However, in recent years, studies have been made to improve the wear resistance and oxidation resistance by containing Al.
There are various cases in which the effect of adding Al is recognized, as typified by Japanese Patent Publication No. 3642 and Japanese Patent Publication No. 5-67705. However, in these cases, the addition of Al to the film merely improves the film itself such as the oxidation resistance and abrasion resistance of the film. Also, TiAl
As a method for improving the adhesion of an N film, JP-A-1-25
As disclosed in Japanese Patent Publication No. 2304, it has been proposed to use a TiN film as a base, but at present it has not yet been possible to obtain sufficient adhesion.

[0003]

Recently, there has been a strong tendency to increase the efficiency of cutting, and the cutting speed and the cutting feed tend to increase. In such a case, as a factor that governs the tool life, the adhesion of the film is more important than the wear resistance and oxidation resistance of the film. The film to which Al is added generally has a high residual compressive stress, and as a result, the adhesion of the film is not sufficiently satisfied. In such high-efficiency cutting, the film is often peeled off, and the life and reliability of the tool are reduced. The result is a loss of performance. Therefore, even in such high-efficiency cutting, it is necessary to further increase the adhesion of the film in order to realize long-life and stable cutting. On the other hand, in order to improve the adhesion, there has been research on reducing the residual compressive stress itself of the film, which is the root cause of the deterioration of the adhesion, but at present it has not yet seen a sufficient effect. .

[0004]

This means that when a high compressive stress is present in the coating, a high shearing stress due to the compressive stress acts on the interface between the coating and the base hard alloy, and this shearing stress is reduced. This is a factor that impairs the adhesion of the film, and suggests that alleviating or removing this results in an improvement in the adhesion of the film. In other words, by interposing a relatively soft layer between the film having a high compressive stress and the base hard alloy, the relatively soft film absorbs and relaxes the shear stress generated at the interface due to the high compressive stress. it is conceivable that.

[0005]

[Object of the present invention] The present inventors have made intensive studies to improve the adhesion of the film, and as a result, by interposing a relatively soft film under the Al-containing film having a high compressive stress, An object of the present invention is to remarkably improve the adhesion of a film by absorbing and relaxing high compressive stress of the film containing Al.

[0006]

The present inventors have conducted various studies on the inner layer interposed as the underlayer, and as a result, have found that the T layer having a relatively low Al content is
i and Al nitrides, carbonitrides, etc. are extremely effective in improving the adhesion. In general, in Ti and Al nitrides, carbonitrides, etc., as the Al content decreases, the hardness increases. It becomes soft. On the other hand, as the Al content increases, the compressive residual stress increases, but the cutting performance tends to improve. Therefore, cutting is performed by interposing Ti and Al nitrides, carbonitrides, and the like having relatively low Al contents under the base such as Ti and Al nitrides, carbonitrides, and the like having a high Al content. It is possible to remarkably improve the adhesion between the nitride and carbonitride layer of Ti and Al having a high content of Al to be coated for improving the performance and the base hard alloy.

As described above, there are cases where a nitride of Ti or the like is used as a base. However, according to a study by the present inventors, it is found that a nitride of Ti or the like containing a small amount of Al is used. Was found to exhibit a much better effect on the improvement of adhesion. This is because the presence of a slight oxide layer, which is always formed on the surface of the base hard alloy when placed in air, significantly deteriorates the adhesion of the film, but a small amount of Al is contained in the film formed as the base. The presence thereof causes a thermite reaction to reduce this oxide layer at the start of coating, thereby removing the oxide layer and resulting in a significant improvement in the adhesion of the film. This is because the oxide of Al has a low free energy of formation and is very easy to form, so the oxygen in the oxide layer on the substrate surface reacts with the ions of Al to form an oxide in the film and remove the oxide layer on the substrate surface. It is based on This reaction cannot occur naturally when a nitride layer or the like of only Ti is used.

[0008] Further, by interposing a softer metal layer under these coatings, it has been possible to obtain a result that the shear stress can be further reduced. This is based on the fact that a metal layer having a higher absorption energy and a lower Young's modulus, in which dislocations easily move, is more effective in absorbing strain energy. In this case, an alloy metal layer of Ti and Al having the same composition as that of the inner layer such as a nitride of Ti and Al used as the underlayer is preferable in terms of adhesion to the inner layer. Needless to say, the above-mentioned thermite reaction occurs even when the alloy metal layer is used as the base as in this case.

[0009] Further, the conditions required for the film to be interposed for the relaxation of shear stress are that the film is soft and that the crystal grains of the layer used as an underlayer as well as the removal of the oxide layer by thermite reaction are relatively coarse. It became clear that the better the surface roughness is, the better the stress is, and the better the surface roughness is, the better the adhesion itself is. As a result of further research from this viewpoint, it has been confirmed that the addition of boron significantly improves the surface roughness, and also tends to coarsen the crystal grains, which leads to a more favorable result for improving the adhesion of the entire film. . Next, the reasons for limiting the numerical values will be described.

In the outer layer, when the content of Al is less than 25%, the effect of adding Al is not recognized, and the wear resistance and oxidation resistance of the coating are not improved. , The hardness decreases and the wear resistance of the film is impaired, so that the Ti / Al ratio is 75 /
25 to 25/75. In the inner layer, when the Al content is less than 2%, the effect of the thermite reaction is small, and when the Al content is more than 25%, the compressive residual stress is increased, and the effect of improving the adhesion of the outer layer is reduced.
The / Al ratio was from 95/5 to 75/25. If the thickness of the intervening inner layer is 0.05 μm or less, there is no effect on stress relaxation, that is, improvement of the adhesion of the film, and if it exceeds 5 μm, a Ti and Al nitride layer originally having a low Al content is used. Has poor abrasion resistance and oxidation resistance.
Since the oxidation resistance is impaired, the thickness is set to 0.05 μ to 5 μ.

When the thickness of the intervening Ti and Al alloy metal layer is 5 nm or less, the effect of stress relaxation, that is, improvement of the adhesion of the film is similarly reduced. When the thickness exceeds 500 nm, plasticity in the alloy metal layer during cutting is reduced. Deformation occurs, and conversely, results in impairing the adhesion of the film, so that the thickness was set to 5 nm to 500 nm. Hereinafter, the present invention will be described in detail based on examples.

[0012]

EXAMPLES Coatings of the present invention and comparative examples were made using a small arc ion plating apparatus under the conditions shown in Table 1 to produce a coated carbide end mill as a trial.

[0013]

[Table 1]

[0014] Boron was added to the target metal and added to the coating. Carbon was added using acetylene gas. In this case, the thickness of the outer layer was unified to 2.0 μm. Perform a cutting test with the following cutting specifications with the obtained end mill,
Cutting was performed until peeling occurred. Table 1 also shows the cutting length at the time when the film flaking of 0.05 mm or more in width occurred on the flank or rake face. As the cutting specifications, the end mill uses an outer diameter of 8 mm, 6 blades, and the work material is SKD11.
(HRC60), the cutting speed was 40 m / min, the feed amount was 0.05 mm / blade, the axial cutting amount was 12 mm, the radial cutting amount was 0.8 mm, and the cutting was performed without cutting oil.

As is clear from Table 1, the end mill in which the nitride and carbonitride layers of Ti and Al having a low Al content are interposed as the base has good adhesion of the coating and has high HRC60.
This realizes stable cutting even when cutting extremely hard steel.

The P40 cemented carbide insert was coated with the coating of the present invention and the comparative example under the coating conditions shown in Table 2 and milled under the following cutting conditions to determine the cutting length until the coating was peeled off. In this case, the thickness of the outer layer film is 3.
It was unified to 0μ. As the cutting specifications, the Slow AA tip uses SEE42TN type, and the work material is SKD61.
(HRC42), the cutting speed was 160 m / min, the feed amount was 0.1 mm / tooth, and the cutting amount was 2 mm. Table 2 also shows the cutting length up to the occurrence of peeling (breakage).

[0017]

[Table 2]

As is clear from Table 2, the insert having a Ti and Al nitride layer or a carbonitride layer with a low Al content has good adhesion of the coating and has a high hardness of HRC42 or higher. This realizes extremely stable cutting even in the milling process.

Next, under the coating conditions shown in Table 3, P
Forty carbide alloys were coated with the coatings of the present invention and comparative examples, and the cutting evaluations shown in Table 2 were performed. Also in this example, the thickness of the outer layer was 3.0 μm. In the coating of the alloy metal, the introduction of nitrogen gas was stopped.

[0020]

[Table 3]

Table 3 also shows the cutting length up to the life of the film at which the film was peeled and the chip was broken. It is clear that the life can be further improved by interposing the alloy metal layer.

[0022]

As described above, peeling of the film is suppressed even in heavy interrupted cutting in which the feed amount per tooth exceeds 0.4 mm in order to improve cutting efficiency, and stable cutting can be performed. Realization has become possible.

Claims (3)

[Claims] 1. An outer layer comprising at least one of a nitride, a carbonitride, a carbonitride, a boronitride, and a carbonitride of Ti and Al having an atomic ratio of Ti / Al of 75/25 to 25/75. A nitride of Ti and Al having an atomic ratio of Ti / Al of 98/2 to 75/25 as an adhesion improving layer of the outer layer between the outer layer and the base hard alloy,
A coated hard alloy characterized by interposing a kind of inner layer selected from carbonitride, boride, and carbonitride. 2. The coated hard alloy according to claim 1, wherein
A coated hard alloy, wherein the thickness of the inner layer is 0.05 μm to 5 μm. 3. The coated hard alloy according to claim 1, wherein a metal alloy layer of Ti and Al having the same atomic ratio as the inner layer having a thickness of 5 nm to 500 nm is interposed between the base hard alloy and the inner layer. A coated hard alloy, characterized in that: