JPH10317087A - Coated titanium cyanide-base cermet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coated cermet having high adhesion to a hard coating layer by constituting the coated cermet so that the microstructure of a base material composed of a TiCN-base cermet is composed essentially of a hard phase with core, having a core part and a peripheral part, and a layer in which the amount of the hard phase with core is reduced is provided to the vicinity of the surface of the base material, at the time of providing the hard coating layer to the surface of the base material. SOLUTION: A TiCN-base cermet having a composition represented, e.g. by TiCN-15%WC-12%Co-4%Ni-8%TaC is sintered by the ordinary powder metallurgy processing. The resultant sintered cermet is ground into a shape of a throw away tip for face milling cutter and subjected to reheating treatment at about 1350 to 1500 deg.C in a reduced pressure or pressure sintering furnace. Subsequently, a TiAlN hard coating layer of about 3 μm thickness is formed by means of PVD by using the above sintered cermet as a base material. By this method, the coated cermet capable of withstanding long use, which is constituted so that the microstructure of the base material is composed essentially of a hard phase with core, having a core part and a peripheral part enclosing the core part, and a layer reduced in the amount of the hard phase with core and/or a layer free from the hard phase with core is provided to the vicinity of the base-material surface, can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated TiCN-based cermet used for materials such as tools.

[0002]

2. Description of the Related Art Conventionally, a cutting tool material in which a hard coating layer is provided on the surface of a TiCN-based cermet has been used. More specifically, a carbon-enriched layer is formed on the surface of a cermet substrate, and a coating layer is further provided thereon.
No. 5 is known. Further, a cermet described in Japanese Patent No. 2578679 as a TiCN-based cermet provided with a modified layer having high toughness and high hardness by increasing the W concentration in the surface layer portion is characterized as a TiC-based cermet having a reduced bonding phase concentration in the surface portion. The cermets described in Japanese Unexamined Patent Publication No. Hei 5-9646 are each known.

[0003]

However, the above-mentioned coated cermet alloy has not yet had sufficient adhesion strength with the hard coating layer. When TiAlN, for example, is provided as the hard coating layer, the hard coating layer is liable to peel off very easily, which promotes abrasion and has a short service life. Further, with respect to the toughness of the cermet, there is a problem that chipping of the cutting edge is apt to occur, and the cermet cannot withstand use under severe conditions. Therefore, the present invention provides a coated cermet which exhibits a strong adhesive strength to the hard coating layer, withstands use for a long time, and has excellent toughness.

[0004]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have studied the alloy structure near the surface of the cermet, and as a result, it has been found that the cermet may be constituted as follows. That is, the microstructure of the base mainly includes a cored hard phase having a core portion and a peripheral portion, and a layer having a reduced cored hard phase and / or a layer not having the cored hard phase near the surface of the base. Is provided.
In the cored hard phase, the core is relatively Ti
Some components, such as rich in W or rich in W, have relatively different concentrations between the core and the periphery.
Hereinafter, the operation and effect will be specifically described based on examples.

[0005]

EXAMPLE The composition was TiCN- by the ordinary powder metallurgy method.
A TiCN-based cermet of 15% WC-12% Co-4% Ni-8% TaC was sintered. This was ground into the shape of a throw-away tip for face milling. The pressure is reduced at four different temperatures from 1350 ° C to 1500 ° C.
The heat treatment was performed again in the pressure sintering furnace. Using this as a substrate, a 3 μm-thick TiAlN coating layer was provided by a known PVD method. still,
The hard coating layer in the present invention is made of the periodic table 4a, 5a, 6
One or more hard materials selected from the group consisting of metallic, carbide, nitride, oxide, hard boron nitride, hard carbon, and solid solutions or mixtures of transition metals of group a or Al In one or two or more layers.
It is obtained by coating with a thickness of 2 to 20 μm. It is not particularly limited to TiAlN. For comparison, a sample was prepared in which reheat treatment after grinding was omitted. Later, the cross-sectional structure of each sample was observed with a scanning electron microscope (SEM), and the results of examining the thickness of the layer in which the cored hard phase was reduced are shown in Table 1.

[0006]

[Table 1]

[0007] From Table 1, in Examples 1 to 4 of the present invention, a layer in which the cored hard phase was reduced from the position of 0.8 to 1.5 µm from the surface of the substrate to the position of 3.2 to 3.8 µm was observed. . Here, the cored hard phase is mainly a B1-type solid solution having a structure in which the core portion is relatively rich in Ti as compared with the peripheral portion.
In the observation by M, the heart was observed darker than the periphery.
On the other hand, in Comparative Example 5, such a layer was not observed.

A cutting test was performed using these samples.
Cutting specifications are: cutting speed 120m / min, feed 0.4mm /
A blade and a work material SKD11 were used. One chip was mounted on a face mill having a diameter of 160 mm, and a work material having a width of 50 mm was cut. At this time, the center of the work material and the center of the face milling machine were set on the same straight line so that the impact was applied to the tip most strongly.
The number of impacts until the chip was broken was measured five times, and the average value was evaluated. The results are collectively shown in Table 1.

From Table 1, it can be seen that the examples of the present invention have a long life, as many as 1.5 times or more the number of impacts before breaking, compared to the comparative example. Since the modified layer structure near the surface of the cermet substrate has a buffering function against impact, the product of the present invention was found to be less prone to chipping and chipping of the cutting edge and to be excellent in strength. The position where the layer having the reduced cored hard phase is provided is preferably a position up to 20 μm, more preferably a position up to 5 μm from the surface of the cermet substrate toward the inside.

[0010]

As described in detail above, the product of the present invention has a good life with less occurrence of chipping and chipping of the cutting edge even in intermittent cutting involving a strong impact.

[Brief description of the drawings]

FIG. 1 shows a micrograph of the structure of a cross section of a substrate of a coated cermet of the present invention observed by SEM.

[Explanation of symbols]

 1 Cermet surface 2 Layer with reduced cored hard phase

Claims (1)

[Claims] 1. A coated TiCN-based cermet in which a hard coating layer is provided on the surface of a TiCN-based cermet substrate, wherein the microstructure of the substrate is mainly a cored hard phase having a core and a peripheral portion, and A coated TiCN-based cermet, wherein a layer having a reduced cored hard phase and / or a layer having no cored hard phase is provided near a surface.