JPH10168584A - Coated hard alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To absorbingly relax the high compressive stress of Al-contg. coating and to improve the adhesion of the coating by interposing a relatively soft secondary hard layer contg. Ta below a primary hard layer contg. Ti and Al. SOLUTION: The surface of a substrate hard alloy is coated with a primary hard 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. A secondary hard layer of at least one kind selected from the nitrides, carbon nitrides, nitrogen borides and carbon nitrogen borides is interposed below te primary coating layer. The thickness of the secondary hard layer is regulated to about 0.05 to 5μm. The secondary hard layer is relatively soft and can relax the shearing stress generated on the boundaries owing to the high compressive stress. Furthermore, in the case a metallic layer of Ta having about 5 to 500nm thickness is interposed into the space between the secondary hard layer and the substrate hard alloy, the shearing stress can moreover be relaxed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a coated hard alloy having excellent wear resistance.

[0002]

2. Description of the Related Art Conventionally, films such as TiN and TiCN have been widely and generally used. However, in recent years, studies have been made to improve wear resistance and oxidation resistance by adding Al, and Japanese Patent Publication No. 4-5
As represented by Japanese Patent No. 3642 and Japanese Patent Publication No. 5-67705, there are various cases in which the effect of adding Al is recognized. 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.

[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 often peels and the life of the tool, reliability 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]

Means for Solving the Problems The present inventors have conducted intensive studies to improve the adhesion of the film, and as a result, have found that a film having a high compressive stress containing Al, such as a nitride of Ti and Al, A relatively soft film ("second hard layer") under a film ("first hard layer") composed of one or more of carbonitride, carbonitride, boride and carbonitride By intervening, the high compressive stress of the Al-containing film is absorbed and relaxed, and as a result, it has been found that the adhesion of the film can be remarkably improved. This indicates that, when a high compressive stress is present in the coating, a high shear stress caused by the compressive stress acts on the interface between the coating and the base hard alloy, and this shear stress is a factor that impairs the adhesion of the coating. It is suggested that relaxing or removing this improves 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] Further, as a result of repeated studies by the present inventors,
By interposing a softer metal layer under these coatings, a result was obtained in which the shear stress could be further reduced. This is based on the fact that a metal layer having a higher absorption energy, a lower Young's modulus and a higher dislocation mobility is more effective at absorbing strain energy. As a result, the feed amount per blade is 0.4mm
Even in heavy intermittent cutting, the peeling of the film is suppressed, and stable cutting can be realized.

According to the study of the present inventors, the condition required for the film to be interposed is not only that the film is soft, but that the relatively coarse crystal grains are more preferable for stress relaxation, and the better the surface roughness, the better the adhesion. It has been found that the results are favorable for improving the properties themselves. One of the most suitable films (“second hard layer”) satisfying these conditions is TaN, T
aBN and the like. In addition, it was confirmed that the addition of boron (B) significantly improved the surface roughness and brought about a more favorable result in improving the adhesion of the entire film. Conventional T
In some cases, iN, TiCN, TiC, etc. are interposed, but according to the study of the present inventors, TiN, TiCN, TiC, etc.
C first has a rough surface and a fine crystal grain of the film to be formed. In addition, the hardness is not sufficiently soft to improve the adhesion of the film, and it is not so effective in absorbing and relaxing the shear stress. As compared with TaN, TaBN, etc., the effect of improving the adhesion of the film was a remarkably low result.

Next, the reasons for limiting the numerical values will be described. When the thickness of the interposed Ta nitride layer, carbonitride layer, boride layer, and carbonitride layer (“second hard layer”) is 0.05 μm or less, stress relaxation, that is, film adhesion When the thickness exceeds 5 μm, the abrasion resistance of the entire film containing Al is impaired, so that the thickness is set to 0.05 μm to 5 μm. When the thickness of the intervening Ta metal layer is 5 nm or less, the effect of stress relaxation, that is, improvement of the adhesion of the film is similarly ineffective. To 5 nm to 500 nm, since this results in a loss of adhesion.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION

Example 1 Using a small-sized arc ion plating apparatus, coating was performed on the examples of the present invention and comparative examples under the conditions shown in Table 1, and a coated carbide end mill was prototyped. Boron was added to the target metal, and the boron-added target metal was added to the coating. Carbon was added using acetylene gas. The film thickness of TiAlN was unified to 2.0 μm.

[0009]

[Table 1]

A cutting test was performed on the obtained end mill under the following cutting conditions. End mill φ8 mm 6 blades Work material SKD11 HRC60 Cutting speed 40 m / min Feed 0.05 mm / tooth Cutting 12 mm x 0.8 mm Cutting Dry (dry) cutting 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 is clear from Table 1, the end mill in which TaN or TaBN or the like is interposed has good adhesion of the coating and realizes stable cutting even when cutting extremely hard steel of HRC60.

Example 2 Under the coating conditions shown in Table 2, a carbide insert equivalent to JISP40 was coated according to the present invention and the comparative example, milling was performed under the following cutting conditions, and the cutting length until the coating was peeled was determined. , And Table 2. Insert JIS P40 equivalent SEE42TN Work material SKD61 HRC42 Cutting speed 160m / min Feed 0.1mm / tooth Cutting depth 2mm Cutting Dry (dry) cutting

[0013]

[Table 2]

As is clear from Table 2, the insert in which TaN or TaBN or the like is interposed has good adhesiveness of the coating and realizes extremely stable cutting even in the milling of high hardness steel of HRC42. is there. In this cutting example, if peeling occurs in the coating, the insert immediately breaks, resulting in an extreme difference in service life.

Example 3 Under the coating conditions shown in Table 3, a cemented carbide according to JIS P40 was coated with the coatings shown in Examples of the present invention and Comparative Examples, and the cutting evaluation shown in Table 2 was performed. Also in this example, the thickness of TiAlN was set to 3.0 μm. Also, Ta
In the metal coating, the introduction of nitrogen gas was stopped. Table 3 also shows the cutting length up to the life until the film is peeled off and is broken.

[0016]

[Table 3]

It is clear that the life can be further improved by interposing the Ta metal. still,
The coating conditions are the same as in Example 2.

[0018]

According to the present invention, even in high-efficiency cutting,
Long life and stable cutting can be realized. In particular, the peeling of the film due to the reduction of residual compressive stress,
Normal wear was obtained due to reduced chipping.

Continued on the front page (72) Inventor Norihiko Shima 13 Shinsen, Narita City, Chiba Prefecture 2 Hitachi Tool Co., Ltd. Narita Factory

Claims (3)

[Claims] 1. A coated hard alloy comprising a base hard alloy coated with a first hard layer comprising at least one of a nitride of Ti and Al, a carbonitride, a carbonitride, a boronitride, and a carbonitride. , Between the first hard layer and the base hard alloy,
A coated hard alloy characterized by interposing at least one second hard layer selected from nitride, carbonitride, boride, and carbonitride. 2. The coated hard alloy according to claim 1, wherein
The coated hard alloy, wherein the thickness of the second hard layer is 0.05 μm to 5 μm. 3. The coated hard alloy according to claim 1, wherein between the base hard alloy and the second hard layer,
A coated hard alloy characterized by interposing a Ta metal layer having a thickness of 5 nm to 500 nm.