JPH10158839A - Coated cemented carbide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain coated cemented carbide showing a high deflective strength value as a substrate, by using WC base cemented carbide contg. a specified ratio of Co as metal bonding phases and coating the surface of this substrate with CVD coating of the carbide or the like of Ti and alumina. SOLUTION: As a substrate, WC base cemented carbide contg. 0.3 to 3wt.% Co as metal bonding phases is used. The surface of this substrate is coated with one or two kinds selected from the carbides, carbon nitrides and nitrides of the metallic elements of the groups 4A (Ti, Zr and Hf), 5A (V, Nb and Ta) and 6A (Cr, Mo and W) in a Periodic Table and alumina by a single layer or double layers. Furthermore, a part or the whole body of Co may be substituted with Ni, In this way, the coated cemented carbide having about 200 to having approximately 100% density ratio and about 200 to 280kgf/mm<2> deflective strength is obtd., by which a CVD coated chip having a long tool service life can be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CVD coated cemented carbide used in the field of cutting and the like, and more particularly to a cemented carbide used for its substrate.

[0002]

2. Description of the Related Art A coated coated cemented carbide indexable insert having a Co content of about 6 to 10% is used as a substrate. A throw-away tip is required to have heat resistance, and if it exceeds 10%, plastic deformation occurs. Therefore, the Co content is usually set to 10% or less. Conversely, if it is less than 6%, the toughness is insufficient, and in many cases, chipping or chipping occurs during cutting. For this reason, the Co content is necessarily limited to approximately 6 to 10%. In addition, in applications where wear resistance is required, the binderless cemented carbide is used in sliding materials as disclosed in Japanese Patent Application Laid-Open No. 4-348873. Is disclosed in JP-A-7-207398, which is binderless.

[0003]

If the Co content is 3
% Or less and if sufficient toughness is obtained, a chip capable of extremely high-speed cutting can be obtained. It is the metal bonded phase, namely Co
For is the Lord. In addition, when coated by CVD, a small amount of metal component diffuses into the film, so that good properties with excellent wear resistance are exhibited. In the conventional sintering means, if the amount of Co is 3% or less, eccentricity of Co occurs to a considerable extent, so that it is inevitable that nests remain and it is difficult to reach a density ratio close to 100%. Co-crystallisation simultaneously increases the WC / WC contact. The WC / WC interface is lower in strength than the WC / Co interface, and microcracks tend to occur. Mainly because of the above reasons, the transverse rupture strength, which is an index of toughness or strength, is at most only 150 kg / mm ^2, which is practically difficult as a base for a coated chip. Although there is a means for eliminating the remaining nests by hot isostatic pressing (hereinafter abbreviated as HIP), it can be confirmed that a cemented carbide having a density ratio of almost 100% can be obtained by using appropriate processing conditions. However, the transverse rupture strength of the alloy thus obtained is at most 1
80 kg / mm ² , which does not conform to the gist of the present invention.
Although the nest disappears, the frequency of WC / WC contacts does not decrease, which is the reason for exhibiting low flexural strength values. Therefore, an object of the present invention is to provide an alloy having a Co content of not more than 3% or less and a density ratio of approximately 100% and exhibiting a high transverse rupture force. .

[0004]

Means for Solving the Problems That is, when Co is 10%
In the following, the WC basically forms a continuous skeleton. The formation time of the skeleton substantially coincides with the early stage of sintering, that is, the time when sintering shrinkage due to neck growth starts. Therefore, the present inventors have conducted intensive studies on a sintering technique that minimizes neck growth in the early stage of sintering, and finally obtained an alloy with a significantly improved transverse rupture strength of 200 to 280 kgf / mm ² . In the present invention, Co is used as a metal binding phase in an amount of 0.1 to 0.1%.
Using a WC-based cemented carbide containing 3 to 3% by weight as a substrate, the substrate is selected from carbides, carbonitrides, nitrides and aluminas of metal elements belonging to groups 4A, 5A and 6A of the periodic table by a chemical vapor deposition method. Coated cemented carbide, characterized in that one or more of the above-mentioned coated cemented carbides are coated in a single layer or multiple layers, and more preferably, in the coated cemented carbide, part or all of Co is replaced with Ni. It is a coated cemented carbide characterized by the above.

[0005]

By adopting the above-mentioned manufacturing method, an unprecedented high-toughness WC-based cemented carbide containing 0.3 to 3% by weight of Co can be obtained, and a CVD-coated chip using the alloy is created. did. Oxidation of WC is accelerated at a cutting edge temperature sufficiently reached in high-speed cutting, that is, around 1000 ° C. The CVD hard coating material currently used for cutting is a single layer of one or more selected from carbides, carbonitrides, nitrides and aluminas of metal elements belonging to groups 4A, 5A and 6A of the periodic table. Or, generally, they are coated in multiple layers, but their oxidation onset temperature is higher than WC. By coating these hard coatings, oxidative wear during cutting is suppressed, and a longer-life chip capable of higher-speed cutting is obtained. Further, the damage caused by cutting of the cemented carbide tip is greatest for Co, which is a metal bonding phase. The wear resistance is improved because the area where the Co metal is in direct contact with the workpiece is reduced by the CVD coating.

[0006] The low Co cemented carbide substrate, which is one of the main elements of the present invention, has a high transverse rupture force than ever before, and therefore exhibits good performance as a cutting tip. The Co content of the cemented carbide is 0.1.
The range of 3 to 3% is compatible with the gist of the present invention. If it exceeds 3%, the heat resistance decreases, and it cannot be used as a high-speed cutting insert, which is the object of the present invention. If it is less than 0.3%, the toughness of the alloy is insufficient and it is difficult for practical use. Even if some or all of Co is replaced with Ni, the mechanical properties of the alloy are almost the same, and therefore do not depart from the gist of the present invention.

[0007] The CVD film is made of 4A, 5A and 6 in the periodic table.
One or two or more single-layer films or multiple films selected from carbides, carbonitrides, nitrides, and aluminas of Group A metal elements, but diamond films and DLC films also exhibit good properties. Particularly, the diamond film does not exhibit good properties in the presence of Co, but the low Co carbide of the present invention can exhibit better properties than ever before. Coating with a Cr compound or a Ta compound according to other uses and purposes also gives good results. Hereinafter, the present invention will be described in detail with reference to examples.

[0008]

EXAMPLE A WC powder having an average particle size of 0.6 μm and a Co having an average particle size of 1.0 μm were formed so as to obtain a composition of 99% WC-1% Co.
The powder was weighed, and 1.5% by weight of a molding wax was added to the mixed powder, followed by wet mixing. Next, it was press-formed into various shapes through the respective steps of drying and granulation. The physical properties of the cemented carbide obtained by sintering this pressed compact by special sintering technology are as follows:
The transverse rupture strength was 250 kg / mm ² and the hardness was HRA94.6.

Using this cemented carbide as a substrate, a Ti
The C-alumina film was coated to a thickness of 7 μm. The indexable insert was attached to a holder, and lathing was performed. For comparison, a cutting test was also performed on a coated indexable insert using a conventional carbide substrate. The processing conditions are as follows. Work: ordinary cast iron Work shape: 4 grooves with φ180 mm and width 10 mm Rotation speed: 700 rotations / min Cutting speed: 400 m / min Feeding: 0.2 mm / rotation Depth of cut: 0.3 mm Although normal wear was exhibited after the lapse of time, the comparative material was broken at 5 minutes after the start of the test. It was determined that this was due to plastic deformation due to cutting heat and thermal cracking.

A WC powder having an average particle size of 1.0 μm and a Co powder having an average particle size of 1.0 μm,
Table 1 in the same manner as in Example 1 using Ni powder of m.
Was produced.

[0011]

[Table 1]

Sample No. 7 is a chip used for comparison. Next, a cutting test was performed in the same manner as in the above example. The processing conditions are as follows. Work: S50C (HRC50) Work shape: φ180 mm Four grooves with a width of 10 mm Rotation speed: 320 rotations / min Cutting speed: 180 m / min Feeding: 0.2 mm / rotation Cutting depth: 0.3 mm Life of each sample number (min) In Example 1 of the present invention, 25 minutes
Is 30 minutes, 3 is 42 minutes, 4 is 30 minutes, 5 is 31
In comparison, the comparative material 7 had reached the end of its life in 3 minutes, while that of Comparative Example 7 was 30 minutes. The product of the present invention thus has a very long life.

[0013]

As described above, the CV according to the present invention is
D-coated inserts have a longer tool life than conventional ones.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Nobunge Adachi 13-2 Shinizumi, Narita City, Chiba Pref.

Claims (2)

[Claims] 1. A WC-based cemented carbide containing 0.3 to 3% by weight of Co as a metal binder phase, and a metal element belonging to Group 4A, 5A or 6A of the periodic table on the substrate by a chemical vapor deposition method. A coated cemented carbide characterized in that one or more selected from carbides, carbonitrides, nitrides and aluminas are coated in a single layer or multiple layers. 2. The coated cemented carbide according to claim 1,
A coated cemented carbide characterized in that part or all of Co is replaced with Ni.