JPS5856033B2 - Coated cemented carbide parts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coated cemented carbide member having excellent wear resistance and viscosity and suitable for use as a cutting tool, particularly as an indexable insert.

Conventionally, a hard phase consisting of one or more of carbides, carbonitrides, carbonates, and carbonitrides of metals in Groups 4a, 5a, and 6a of the periodic table: 60 to 97 wt. One of the Fe group metals, containing one or more of the Cr group metals, Sl, and All as necessary.
Bonded phase consisting of a species or two or more species and unavoidable impurities:
The carbides, nitrides, carbonates, and carbonitrides of metals of the 4a, 5a, and 6a groups are deposited on the surface of a cemented carbide base material having a weight of 3 to 40 φ by chemical vapor deposition or physical vapor deposition. , Al oxide, and a single layer consisting of one type of solid solution of two or more of these components or a multilayer hard layer consisting of two or more types coated with a layer thickness of 2 to 20 μm. A coated cemented carbide member has been proposed, and this coated cemented carbide member has high wear resistance, oxidation resistance, and diffusion wear resistance due to the formation of the hard layer, and has a long cutting tool life. Although the toughness of the cemented carbide base material is improved by 2 to 10 times compared to that without the hard layer, on the other hand, the toughness of the cemented carbide base material decreases (20 to 40% in transverse rupture strength). As a result, the numerous cracks generated in the hard layer due to the high stress during cutting propagate to the cemented carbide base material, resulting in chipping and breakage. I couldn't avoid doing it.

Although the coated cemented carbide member has improved wear resistance due to the formation of the hard layer, the toughness of the cemented carbide base material decreases, which limits its use. The current situation is that

From the above-mentioned viewpoint, the present invention provides a coated cemented carbide member that has excellent wear resistance and viscosity and can be applied to any purpose. A hard phase consisting of one or more of carbides, carbonitrides, carbonates, and carbonitrides of metals: 60 to 97% by weight, and optionally Cr group metals, Si, and Al. A binder phase consisting of one or more Fe group metals and unavoidable impurities: 3 to 40 weight φ. , carbides, nitrides, carbonates, carbonitrides, and carbonitrides of metals of Groups 4a, 5a, and 6a, and Al oxides, as well as solid solutions of two or more of these components. Abrasion resistance is imparted by coating a known hard layer of a single layer consisting of one type or a multilayer consisting of two or more types, and the cemented carbide base material is coated with a layer thickness of 50 to 500 μm that does not contain free carbon. It consists of a surface layer part and a core part containing free carbon of 0.01 to 05 weight φ, and the surface layer part has a hardness of 10φ continuous from the inside to the surface of the base material.
It is characterized in that toughness is imparted by the presence of a softened layer that decreases the toughness.

In the production of the coated cemented carbide member of the present invention, when forming a hard layer on the surface of the cemented carbide base material, carbon in the base material diffuses and moves to the hard layer. If a hard layer is formed using a cemented carbide base material that does not have a hard surface, lower carbides that inhibit toughness will be generated in the surface layer of the base material directly below the hard layer, making it impossible to secure a softened layer. As the cemented carbide base material before forming the hard layer, one containing free carbon is used, and when the hard layer is formed, the free carbon diffuses into the hard layer, and the surface layer of the base material contains free carbon. It is necessary to suppress the formation of lower carbides that impair toughness.

However, even if a hard layer is simply formed on the surface of a cemented carbide base material containing free carbon, 1a%
It is not possible to form a softened layer with a gradient of hardness (Hardness to Vickers Hardness), but it is necessary to decarburize the surface layer of the cemented carbide base material in advance and carburize it if necessary. A hard layer is formed in a state in which a soft layer is formed and also contains free carbon, and as a result, the base material is coated with 10% of the hard layer continuously from the inside to the surface.
% or more of hardness is present, and a surface layer portion containing no free carbon is formed.

Next, in the coated cemented carbide member of the present invention, the reason why the layer thickness of the surface layer, the free carbon content of the core, and the continuous hardness gradient in the softened layer are limited as described above will be explained.

(a) Layer thickness of the surface layer If the layer thickness is less than 50 μm, the desired toughness cannot be secured, and therefore chipping or damage will occur during cutting. On the other hand, if the layer thickness exceeds 500 μm, Since the strength will deteriorate, the layer thickness will be reduced to 5.
It was determined to be 0 to 500 μm.

(b) Free carbon content in the core If the content is less than 0.01φ, the desired strength cannot be secured in the core, while if the content exceeds 0.5%, the toughness of the core decreases. Therefore, its content was determined to be 0.01 to 0.5%.

(c) Continuous hardness gradient in the softened layer In order to prevent the propagation of cracks that occur in the surface layer when used as a tool (well, it is necessary to provide a softened layer with high toughness and low hardness, If the continuous hardness gradient is less than 10%, the core and the softened layer will have a clear boundary, or the softened layer will have undulations with a hardness gradient, and variations in the boundary and gradient will occur. Since peeling and internal cracks may occur at points, which is undesirable, it is necessary to continuously reduce the hardness by at least 10 Vickers hardness from the core side to the surface of the base material.

Next, the coated cemented carbide member of the present invention will be explained using examples.

Example 1 Free carbon: Has a composition of WC-6% Co containing 0.1 weight range, and further has a chip shape: CIS.

Cemented carbide substrates with SNMN432: 20 pieces were produced by conventional powder metallurgy methods.

Next, 15 of the above base materials were charged into the furnace and heated to H2-
Decarburization treatment was performed using H20 mixed gas and maintaining the temperature at 10,000C for 5 hours.

When the surface layer of the resulting surface-decarburized base material was analyzed by X-ray diffraction, W3Co3C9 was observed over a layer thickness of 50 μm.
The existence of a softened layer in which W2C9 and W peaks appeared strongly was confirmed.

Next, five of the surface-decarburized substrates were heated to 1200°C, 1250°C, and 1300°C, respectively, and carburized using a H2-5% CH4 mixed gas for 3 hours. to add 0.0% free carbon to the softened layer.
After containing 01%, 0.05%, and 0.5% *1, reaction temperature: 1000°C, furnace internal pressure 100Hg.

Reaction gas composition: 96φH2-2φTi (J!4-2 section C
H4, reaction time: 2 hours, a hard layer made of TiC was coated on the surface of the base material to produce coated cemented carbide members of the present invention (hereinafter referred to as coated members of the present invention) 1 to 3.

For the purpose of comparison, the remaining 5 of the above base materials
A hard layer was directly formed on the sample under the above conditions to produce a comparative coated cemented carbide member (hereinafter referred to as a comparative coated member) 1.

The above-mentioned coated members 1 to 3 of the present invention and the above-mentioned comparative coated member 1
The characteristics (average values of 5) are shown in Table 1.

As shown in Table 1, both the coated member of the present invention and the comparative coated member have a surface layer portion that does not contain free carbon, but in the coated member of the present invention, the hardness of the surface layer portion, In particular, the hardness of the base material surface is 1 compared to the base material core.
In contrast, in the comparative coated member, there is almost no difference between the base material surface hardness and the base material core hardness, and the softened layer is present. Turns out it doesn't exist.

Next, regarding the above-mentioned coated members 1 to 3 of the present invention and comparison coated member 1, work material: JIs, SNCM-8 square material (hardness HB: 30
An interrupted cutting test was conducted under the following conditions: cutting speed: 100 m/mjn, feed: 0.35 mm/rev, depth of cut: 2 mm, and the time until breakage was measured.

Table 2 shows the measurement results (average of 5 measurements).

As shown in Table 2, coated members 1 to 3 of the present invention in which a softening layer is present on the surface layer of the base material all have significantly superior cutting properties compared to comparative coated member 1 in which a softening layer is not present. That is clear.

Example 2 The composition was WC-8% Co containing 0.15% free carbon, and the chip shape was CIS.

Cemented carbide substrates with SNMN432: 20 pieces were produced by conventional powder metallurgy methods.

Then, 10 of the above base materials were charged into the furnace and heated to H2-
Using CO2 mixed gas, oxidation decarburization treatment was performed at a temperature of 800°C for 3 hours to form a layer thickness of 30μ on the surface layer of the base material.
After forming a decarburized softening layer of 0 m, followed by a temperature of 1 in vacuum.
The core carbon is diffused into the softened layer by heating at 400°C for 1 hour to contain 0.01 weight φ of free carbon, and then: Reaction temperature: 1000°C1 Furnace pressure 100 mvtH & Reaction gas composition :67%H2-2%TiC141CH4
A hard layer consisting of TlCo, 2No, and 8 was coated under the following conditions: -30% N2, reaction time: 2 hours, and the coated member 4 of the present invention was manufactured.

For the purpose of comparison, the remaining 10 of the above substrates were coated with a hard layer directly under the above conditions without being subjected to the above oxidation decarburization and free carbon formation treatment. Part 2 was manufactured.

Characteristics of the above-mentioned coated member 4 of the present invention and comparative coated member 2 (1
0 average values) are shown in Table 3.

As is clear from the results shown in Table 3, the results of Example 2 are similar to those of Example 1.

Next, for each 10 pieces of the above-mentioned coated member 4 of the present invention and comparison coated member 2, the following was carried out: Work material: JIS, SNCM-8 square material (hardness HB: 300
), Cutting speed: 80m/m1n1 Feed: 0.45mm/rev, Depth of cut: 2 cuts, When an interrupted cutting test was conducted under the following conditions, the comparative coated member 2 was all damaged within 10 times, whereas All of the coated members 4 of the present invention did not break even after being cut 1000 times, and exhibited excellent cutting characteristics.

As mentioned above, the coated cemented carbide member of the present invention has a softened layer in the surface layer portion that does not contain free carbon of the cemented carbide base material,
Moreover, since the softened layer is in its softest state immediately below the hard layer, cracks generated in the hard layer during cutting will not propagate inside the cemented carbide base material due to the presence of the softened layer. It has industrially useful properties such as almost no occurrence of chipping or defects and can be used in a wide range of applications.

Claims (1)

[Scope of Claims] 1. A hard phase consisting of one or more types of carbides, carbonitrides, carbonates, and carbonitrides of metals in Groups 4a, 5a, and 6a of the periodic table: 60-60 97 weight Da, Cr group metal Si, and one of Al as necessary.
Binding phase consisting of one or more Fe group metals and unavoidable impurities: 3
~40% by weight, carbides, nitrides, carbonates, carbonitrides, and carbonitrides of the metals of groups 4a, 5a, and 6a, and Al
In a coated cemented carbide member which is coated with a single layer or a multi-layer hard layer made of an oxide and a solid solution of two or more of these components, The hard metal base material is composed of a surface layer that does not contain free carbon and has a layer thickness of 50 to 500 μm, and a core that contains free carbon in an amount of 0.01 to 0.5% by weight. The hardness is 1a% continuously over the surface of the base material.
A coated cemented carbide member characterized in that there is a softening layer that reduces the softening of the material.