JPH02311202A - Covered cutting tool - Google Patents

Abstract

PURPOSE:To prevent cracks from spread in coating film and improve resilience by providing a mixture of a granulated crystal structure and columnar crystal structure as a crystal structure in hard coating film. CONSTITUTION:A base metal of sintered hard alloy is coated with a hard film formed of one or at least two layers of compound selected from carbide, nitride, carbonitride, acid nitride, etc. in the 4a-6a groups on the periodic law table. In the method of information, the cemented hard alloy is used for the base metal. A columnar crystal Tin film is formed by a CVD method at about 1,000 deg.C of substrate temperature for about 6 hours in a mixture flow having about 45% H2, about 5% TiCL4, about 50% N2 and about 60mbar pressure in a fur nace and then the pressure in the furnace is raised to about 800mbar to deposit a granulated crystal structure Tin in a cavity of the columnar crystal Tin for forming a coating film having a mixture of about 10mum thick columnar crystal structure and granulated crystal structure. Thus, the resilience of the hard film is remarkably improved and the breakage resisting performance is improved without degrading the antiwear property.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a cutting tool having a hard film formed on its surface.

(Prior art) Conventionally, cermets, cemented carbide, ceramics, etc. have been mainly used as cutting tools, but in recent years, chemical vapor deposition (CVD) has been applied to the surfaces of these as base materials.
D) etc., so-called coated cutting tools are known in which a hard film with excellent wear resistance is formed. Usually, this hard film contains carbides, nitrides, carbonitrides, carbonates, nitrides, and carbonitrides of Groups 4a, 5a, or 68 of the periodic table, or oxides and oxides of ^l. 1 selected from nitrides
A single layer or a multilayer of two or more types is used.

(Problem to be solved by the invention) However, although these hard films have high hardness and excellent wear resistance, they have extremely low toughness, so cracks and cracks occur in the hard film itself.
) and cracks were likely to occur. Therefore, in coated cutting tools, the cracks, cracks, etc. that occur in the coating become notches, and the coated cutting tool as a whole has the disadvantage that the toughness and fracture resistance are significantly deteriorated compared to uncoated cutting tools.

(Objective of the Invention) The main purpose of the present invention is to solve the above-mentioned problems, without deteriorating wear resistance.
The purpose of the present invention is to provide a long-life coated cutting tool with excellent fracture resistance.

(Means for Solving the Problems) As a result of repeated research regarding the above problems, the inventors found that by mixing a granular crystal structure and a columnar crystal structure as the crystal structure of the coating layer, it is possible to solve the problem in a hard coating. It was found that the coating can prevent crack propagation and improve the toughness of the coating itself, and improve the chipping resistance of the coated cutting tool as a whole without impairing its wear resistance.

That is, the present invention uses a material known as a high-strength material such as cermet, cemented carbide, and silicon nitride material as a base material, and the surface of this base material is coated with materials belonging to groups 4a, 5a, and 68 of the periodic table. A single layer or multilayer coating of one or more selected from carbides, nitrides, carbonitrides, carbonates, nitrides, oxycarbonitrides, or 81 oxides and oxynitrides. The cutting tool is characterized in that the coating layer has a structure in which a columnar crystal structure and a granular crystal Mi structure are mixed.

Generally, by chemical vapor deposition (CVD), carbides, nitrides of Groups 4a, 58, and 68 of the periodic table,
When carbonitrides, carbonates, nitrides, and oxycarbonitrides are formed, nuclei are first generated on the surface of the base material, and these nuclei grow further to finally form a film, but this growth process Depending on the reaction conditions, crystallographic structures are classified into roughly two types: columnar crystals that grow with so-called crystal orientation, and granular crystals that grow randomly without orientation. Of these, the latter is generally used for the structure of the coating in coated cutting tools.

The reaction conditions for generating these two types of tissue structures are:
In addition to the basic conditions of substrate temperature, raw material gas concentration, and furnace pressure, it is determined by various factors such as the type of raw material gas, plasma state, and properties of the furnace mouth body. The following can be said. A columnar crystal structure can be obtained by increasing the substrate temperature and decreasing the furnace pressure and raw material gas supersaturation under conditions that normally produce a granular crystal structure. This can be said to be the same tendency in any of the metal carbides, nitrides, carbonitrides, etc. mentioned above.

Specifically, for example, when generating a TiN film, the substrate temperature is 1000°C, H245χ, TiC145χ, N250χ
When produced in a mixed gas flow with an internal pressure of 100 mbar, columnar crystals as shown in the electron micrograph of FIG. 1 are produced. On the other hand, among the above reaction conditions, the furnace pressure was set to 80
When the temperature is changed to 0 mbar, granular crystals as shown in the electron micrograph of FIG. 2 are produced.

The characteristics of the present invention are such two types of organizational structures, namely:
The point is that a film having a texture structure in which columnar crystals and granular crystals are mixed is produced. In order to obtain such a structure, first, columnar crystals as shown in Fig. 1 are formed on a substrate, and then granular crystals as shown in Fig. 2 are formed. As it is clear from Fig. 1, granular crystals form and grow in the voids existing in the columnar crystals, and finally columnar crystals and granular crystals are formed as shown in the electron micrograph of Fig. 3. A hard film with a mixed structure of crystals and crystals is obtained. In such a mixed structure, it is desirable that the volume ratio of columnar crystals and granular crystals be 10:90 to 90:10, especially 300 to 70:30, and if there are too many columnar crystals, On the contrary, the properties of the film tend to deteriorate, and if there are too many granular crystals, there is almost no effect of the presence of columnar crystals, and the object of the present invention may not be achieved.

In coated cutting tools, the above-mentioned crystal-mixed structure exists as a single layer on the tool base material, and even if it exists as one layer in a multilayered hard film, it may cause crank propagation within the hard film. This can be prevented by the tissue formation layer.

In addition, as the tool base material used in the present invention, any conventionally known base material for coated cutting tools can be adopted, such as those mainly composed of WC-Co or mainly composed of TiC, T1CN, etc. and carbides of Group 48, Group 5a, and Group 68 of the periodic table as the hard phase,
Cemented carbide and cermet sintered bodies containing nitrides, carbonitrides, carbonates, nitrides, and oxycarbonitrides, silicon nitrides, silicon nitrides, and silicon nitrides in addition to oxides of group A of the periodic table, Ah (h, 5t(h, Mg
A silicon nitride sintered body containing O, Zr0z, etc. is used, but among these, cemented carbide is the most effective as a base material.

On the other hand, the hard film contains Ti, Zr, 11 [group 48 of the isoperiodic law,
Group 58 such as Ta, Nb, and V, and Group 68 such as Cr.
It is a single layer or multilayer of one or more types selected from carbides, nitrides, carbonitrides, oxycarbonitrides, old oxides, and oxynitrides of the group, and among these, the above-mentioned mixtures. Examples of compounds capable of forming a texture forming layer include compounds having a cubic crystal structure other than butyric compounds. Among these, TiC, TiN, T1CN, and TiCN0 are the most desirable, and the above-mentioned He1 compound is generally used as the outermost layer. It is formed.

These hard films are formed on the base material with a thickness of 5 to 20 μm, and among these, it is desirable that the mixed structure forming layer exists with a thickness of 2 μm or more, and when it is less than 2 μm, the effect of the mixed structure is fully exhibited. Not done.

The invention will now be explained with the following examples.

(Example 1) 15OP30 (made of cemented carbide, model number CNMG1) was used as the base material.
20408) using the known CVO method at a substrate temperature of 10
00℃, Hz45X, TiCIt5χ, N250χ,
A columnar TiN film was produced for 6 hours in a mixed air flow with a furnace pressure of 60 mbar, and then the furnace pressure was increased to 80 On+bar to precipitate granular TiN in the voids of the columnar TiN to form a columnar crystal structure with a film thickness of 10 μm. A film containing a granular crystal structure was formed.

For comparison, a 10 μm film of only columnar TiN was formed on the base material of the same grade under the same conditions as described above, and a 10 μm film of only granular TiN was formed in the same manner.

A cutting test was conducted on the three samples obtained above under the following conditions.

Wear test Work material SCM435R Cutting speed 1
50 m/min Feed: 0.3 mm/rev Depth of cut: 2 mm Time: 15 minutes After cutting, the amount of flank wear was measured under the above conditions.

Fracture resistance test Work material: SCM435 (4 grooves of 10 mm width) Cutting speed: 80 marks/m1n - Only - Feed: 0.3 mm/rev Depth of cut: 3 cycles Number of impacts: Approximately 500 times Each sample was cut under the above conditions. (30 pieces each), the percentage of missing pieces (missing rate) was determined.

The results are shown in Table 1.

[Margin below]

As is clear from Table 1, the columnar TiN film is inferior in terms of flank wear, but the mixed TiN film and the granular TiN film are inferior.
N was at the same level. It was found that the mixed TiN film was superior to other single films in terms of defectiveness, and it was understood that the toughness of the film was improved.

(Example 2) Using the same tool base material and CVD method as in Example 1, H292χ, TiC144χ, c were prepared at a substrate temperature of 1150°C.
An acicular TiC film was formed in a mixed air flow with H4,4χ and a furnace pressure of 60 mbar for 4 hours, and then the temperature was lowered to 1020°C to precipitate a granular TiC film. A coating with a mixed crystal structure was created.

As a comparative example, a film was prepared in which only a columnar decrystallized Tic film and only a granular TiC film were formed, each having a film thickness of 10 μm under the above-mentioned conditions.

These were subjected to wear tests and fracture resistance tests in the same manner as in Example 1, and the results are shown in Table 2.

[Margin below]

= 11-Table 2 According to the results shown in Table 2, the mixed TiC film showed excellent characteristics as in Example 1.

(Example 3) Using the same tool base material and CVO method as in Example 1, H292χ, TiC1a4χ, C
A columnar TiC film was formed for 2 hours in a mixed gas flow with I+4.4χ and a furnace pressure of 50 mbar, and then the temperature was raised to 100°.
C to precipitate a granular TiC film with a film thickness of 7 μm.
The coating is a mixture of a columnar crystal structure and a granular crystal structure, and on top of that, H260χ, CO□14χ,
lICl3χ, A10320χ, furnace pressure 50 mbar
An AlzOi film having a thickness of 3 μm was deposited in a mixed air flow to create a TiC+ΔI2O3 multilayer film with a total thickness of 10 μm.

In addition, as a comparison product, only columnar crystal TiC was made with A1□0 of 7 μm.
3 films with a thickness of 3 μm, and A with only granular crystal Tic of 7 μm.
A 3 μm thick l2O3 film was prepared and tested in the same manner as in Example 1. The results are shown in Table 3.

[Margin below]

(Effects of the Invention) As detailed above, according to the present invention, the toughness of the hard film can be significantly improved by forming a structure in which columnar crystals and granular crystals are mixed in the hard film. As a coated cutting tool, chipping resistance can be improved without deteriorating wear resistance. Therefore, by using these tools, cutting stability and long life can be obtained.

[Brief explanation of drawings]

Fig. 1 is an electron micrograph showing the structure of a columnar crystalline TiN film, Fig. 2 is an electron micrograph showing the structure of a granular crystalline TiN film, and Fig. 3 is a columnar crystalline TiN film and a granular crystalline TiN film. It is an electron micrograph showing the tissue structure of a film in which a film is mixed with a film.

Claims (1)

[Claims] The surface of the tool base material made of high-strength material is coated with carbides, nitrides, carbonitrides, carbonates, oxynitrides, oxycarbonitrides of metals from Groups 4a, 5a and 6a of the periodic table, or Al. In a coated cutting tool coated with a hard film consisting of one or more single or multiple layers of oxides and oxynitrides, columnar crystals and granular crystals coexist in the hard film. A coated cutting tool characterized by having a textured structure.