JPH04331007A - Ceramic cutting tool - Google Patents

Abstract

PURPOSE:To enable cutting of a highly hard material at high efficiency and for extended time by combining a specified base material with coated layers to increase the toughness of the base material ceramics and reduce the coefficient of friction. CONSTITUTION:An alumina ceramic sintered body containing at least one compound, selected from Ti carbide, nitride, carbon nitride or carbon nitrogen oxide of 10 to 50 in weight%, in an Al2O3 matrix is used as a base material. Coating layers of Ti carbide, nitride or carbon nitride, or combinations theirof of 0.2 to 10mum in total thickness are formed on the surface of the base material by PVD or CVD method. A surface compressive residual stress produced on the coated layers increases the toughness of the ceramic sintered body and, since a coefficient of friction of the coated layers is smaller than that of the surface of the ground ceramic sintered body, exhaust of metal chip is smooth to reduce cutting resistance.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alumina ceramic cutting tool capable of cutting highly hard materials with high efficiency.

0002

[Prior Art] High hardness materials such as alloy tool steels, especially Rockwell C hardness (HRC) of 50 or more or Vickers hardness (
High hardness materials with a hardness of 500 Kgf/mm2 or more are extremely difficult to machine, especially to the extent that they can hardly be cut with cutting tools such as ordinary cemented carbide.

Conventionally, for cutting such high-hardness materials, cutting tools made of cubic boron nitride (CBN) sintered bodies or alumina-based sintered bodies such as Al2O3-TiC ceramic sintered bodies called black ceramics have been used. Cutting tools made of solids were used.

However, since CBN sintered cutting tools require ultra-high pressure and ultra-high temperature in the manufacturing process, they are extremely expensive compared to cemented carbide cutting tools, and the shapes of the tools that can be manufactured are limited. However, there were also drawbacks such as significant limitations. On the other hand, although black ceramic cutting tools are inexpensive and have considerable flexibility in tool shape, when actually cutting high-hardness materials, the lack of toughness is noticeable and chipping and flaking are likely to occur, making stable cutting difficult. The reality is that it is difficult to do so.

[0005] As described above, it is thought that the reason why it becomes difficult to cut high-hardness materials is that the thrust force among the three components of the cutting force becomes extremely large. There is a need to improve the strength and toughness of certain alumina-based ceramic sintered cutting tools such as black ceramics.

[0006] Conventionally, therefore, A
A method of reducing the grain size of Al2O3 crystal particles and TiC particles by HIP treatment for l2O3-based ceramic sintered bodies (Japanese Patent Publication No. 1-22223), or Nb,
A method has been proposed in which the strength of the sintered body is improved by adding V, Zr, Ta, Hf, etc. in the form of metals or oxides to uniformly and finely disperse TiC (Japanese Patent Publication No. 63-35587). These methods have made it possible to eliminate pores in the sintered body and improve its strength and hardness. I can't say it's sexual enough.

[0007] In addition to the above method, there is also a method of lapping the rake face of a cutting tool to facilitate the discharge of chips to reduce cutting resistance. Naturally, it is possible to reduce the cutting resistance by installing a breaker, etc., but this method is not widely used because ceramic cutting tools have concerns about their strength and are also subject to manufacturing constraints.

[0008]

Problems to be Solved by the Invention In view of the above-mentioned conventional circumstances, the present invention essentially consists of a low-cost alumina-based ceramic sintered body such as Al2O3-TiC system, and has an HRC rating of 5.
It is an object of the present invention to provide a ceramic cutting tool that can cut high-hardness materials of 0 or more or 500 Kgf/mm2 or more at HV with high efficiency and long life.

[0009]

[Means for Solving the Problems] In order to achieve the above object, in the ceramic cutting tool of the present invention, Al2O
3 10-50% by weight of Ti carbide in the matrix,
A base material of an alumina ceramic sintered body containing at least one compound selected from nitride, carbonitride, or carbonitride, and Ti carbide, nitride, or carbonitride provided on the surface of the base material. It is characterized by comprising a coating layer having a total thickness of 0.2 to 10 μm consisting of a material or a combination thereof.

0010

[Function] In the present invention, by combining the specific base material and the coating layer, the surface compressive residual stress generated in the coating layer improves the toughness of the Al2O3 ceramic sintered body, which is the base material, and reduces the friction of the coating layer. Conventional Al2O with modulus ground
Since it is smaller than the friction coefficient of the surface of a ceramic sintered body such as 3-TiC, chips can be easily discharged and cutting resistance can be reduced. As a result, the ceramic cutting tool of the present invention has excellent toughness and wear resistance for cutting high-hardness materials, and has a service life several times longer than conventional ceramic cutting tools made of Al2O3-TiC-based sintered bodies that do not have a coating layer. This enables efficient and stable cutting.

In particular, the outermost layer of the covering layer is preferably made of TiN, whether the covering layer is a single layer or a multilayer. This is because TiN has a smaller coefficient of friction than TiC and TiCN, and is more effective in reducing cutting resistance when cutting high-hardness materials.

[0012] The alumina ceramic sintered body serving as the base material contains at least one Ti carbide, nitride, carbonitride, or carbonitride of Ti in a matrix of Al2O3.
It contains two compounds. These Al2O3
BACKGROUND ART Ceramic sintered bodies have high strength and hardness, and have traditionally been used as cutting tools for high-hardness materials. However, if the amount of Ti carbide, nitride, carbonitride or carbonitride added is less than 10% by weight, the strength and hardness of the sintered body will be low, or If it exceeds 50% by weight, sinterability will deteriorate, so 1
The range is 0 to 50% by weight.

[0013] The method for manufacturing the above-mentioned sintered body serving as the base material is known, and the raw material powder composition mixed in a predetermined ratio is
Sintering may be performed at a temperature of about 0 to 1900°C. The hot press method is preferred as the sintering method, but ordinary sintering and HI
It is also possible to adopt the P method. Furthermore, during sintering, it is a matter of course that known sintering aids such as NiO, Y2O3, MgO, etc. may be used as additives.

[0014] The coating layer provided on the surface of the base material consists of a single layer of Ti carbide, nitride or carbonitride, or a multilayer combination of these. Regardless of whether it is a single layer or a multilayer, the total thickness of the coating layer is in the range of 0.2 to 10 μm. The reason for this is that if the film thickness is less than 0.2 μm, the effect of improving toughness and wear resistance will be small, and if it exceeds 10 μm, the toughness of the coating layer itself will decrease.

[0015] To form the above-mentioned coating layer, a film forming method by physical or chemical deposition from a gas phase, such as a known PVD method or CVD method, can be used.

[0016]

[Example] Al2O3 powder with an average particle size of 0.4 μm is mixed with 30% by volume of TiC powder with an average particle size of 1.0 μm. After filling this mixed powder into a graphite die, it is placed under a pressure of 30 MPa in argon gas. Hot press sintering was performed at 1650° C. for 1 hour to produce a sintered body in the shape of a cutting tip with model number SNGN120408.

The obtained Al2O3-TiC sintered body was used as a base material, and the coating layers shown in Table 1 were formed on its surface by the usual PVD method, and cutting chips A to G (however, cutting chips F and G (Comparative example) was prepared. In addition, a cutting tip H (comparative example) consisting of only an Al2O3-TiC sintered body without forming a coating layer was also prepared.

Next, a cutting test was conducted under the following conditions using each of the cutting tips A to H. Cutting conditions: Work material...SKD11 (HRC 60) Cutting speed...100m/min. Feed…0.1mm/rev. Depth of cut…1.0mm Holder…FN11R44A Cutting oil…Dry cutting time…10min.

In the above cutting test, the peeling state of the coating layer of each cutting tip was observed, and the flank wear width was measured for each cutting tip after the test, and the results are also listed in Table 1 as the cutting test results.

[0020]

[Table 1]

[0021]

[Effects of the Invention] According to the present invention, a low-cost ceramic with high toughness and excellent wear resistance is capable of cutting high-hardness materials with HRC of 50 or more or HV of 500 Kgf/mm2 or more with high efficiency and long life. Cutting tools can be provided.

Claims (2)

[Claims] Claim 1: 10 to 5 in the Al2O3 matrix
A base material of an alumina ceramic sintered body containing 0% by weight of at least one compound selected from Ti carbide, nitride, carbonitride, or carbonitride, and a Ti provided on the surface of the base material. A ceramic cutting tool comprising: a coating layer having a total thickness of 0.2 to 10 μm and consisting of carbide, nitride, carbonitride, or a combination thereof. 2. The ceramic cutting tool according to claim 1, wherein the outermost layer of the coating layer is TiN.