JP3033169B2 - Diamond-coated indexable insert and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a diamond-coated high-hardness material and a throw-away insert that can cut various light alloys such as an Al-Si alloy at a high speed for a long time. .

(B) Conventional technology As a surface coating tool, PVD method or C
Surface-coated indexable inserts in which a single layer or multiple layers of carbides, nitrides, carbonitrides, and oxides of Al, Ti, Hf, and Zr are formed by the VD method are widely used.

In addition, since diamond has extremely high hardness and is chemically stable, it hardly reacts with Al, Cu and alloys of light metals used for practical use. Therefore, when adapted to a cutting tool, when cutting such light metals or their alloys at high speed using diamond, the finished surface of the work material is extremely excellent, so that a single crystal,
Sintered diamond cutting tools or diamond coated cutting tools are widely used in practice.

(C) Problems to be Solved by the Invention However, since many diamond-coated tools have insufficient adhesion strength between the substrate and the diamond-coated layer, the life of the diamond-coated layer is often extended by peeling of the diamond-coated layer. The reasons for this are as follows: 1) Diamond is an extremely stable substance and does not form a compound with any substance, so that the diamond coating layer and the base material are joined by intermolecular attraction. As for the intermolecular attractive force, the adhesion strength to the substrate is lower than that of the coating layer bonded by forming a chemical compound.

2) The coefficient of thermal expansion between the diamond and the substrate is significantly different,
Residual stress is generated in the diamond coating layer. Therefore, the adhesion strength is low.

There are two possibilities.

As the contact area between the substrate and the diamond coating layer increases, the intermolecular attraction increases, and the adhesion strength of the diamond coating layer to the substrate increases. The higher the nucleation density of diamond on the surface of the substrate, the larger the contact area between the substrate and the diamond coating layer.

As means for realizing these, specifically, a diamond abrasive grain is used to damage the base material, or the diamond abrasive grain and the base material are thrown into water, ultrasonic vibration is applied, and the base material is The surface of the base material has been treated, for example, by damaging the base material or etching the base material with an acid or alkali to make fine irregularities on the base material surface and increasing the surface area of the base material. At present, a diamond coating layer having sufficient adhesion strength has not been obtained.

In Japanese Patent Application Laid-Open No. 61-291493, a sintered body mainly composed of Si ₃ N ₄ and a sintered body mainly composed of SiC are proposed as substrates having substantially the same thermal expansion coefficient as diamond. doing. By using these, the peeling phenomenon of the diamond coating layer due to residual thermal stress was not observed, but there was still a problem of surface treatment, and a diamond coating layer having sufficient adhesion strength with the base material has not yet been obtained. is the current situation.

B. Structure of the invention Therefore, in researching and developing a diamond coating layer and a substrate having excellent peeling resistance, for the reasons described above, the present inventors focused on the surface state of the substrate and repeated the research. As a result, when the base material is formed by molding and sintering a mixed powder mainly composed of Si ₃ N ₄ , and when the diamond coating layer is formed on the base material whose surface is in a sintered skin state, it has a high adhesion strength Was found.

Furthermore, after sintering, the substrate once ground is heat-treated again to obtain a sintered surface before grinding the surface (hereinafter referred to as a heat-treated surface). It has been found that when formed, it has high adhesion strength.

The reason why the sintered body containing Si ₃ N ₄ as a main component was selected as the base material is that the thermal expansion coefficient of Si ₃ N ₄ is close to that of diamond and the thermal expansion coefficient is hardly generated.

Furthermore, the surface of the base material created by molding and sintering a mixed powder containing Si ₃ N ₄ as a main component has coarse columnar crystals because the columnar crystal structure of Si ₃ N ₄ grows freely. . The following two points can be considered as effects due to the presence of the columnar crystal structure that has grown freely.

1) Since the columnar structure of Si ₃ N _{4 on} the surface grows freely,
It becomes a coarse columnar crystal. For this reason, the surface has irregularities as compared with the ground surface, and the contact area between the substrate and the diamond coating layer increases.

2) The crystal grain boundary becomes a singular point, and nucleation of diamond is likely to occur.

On the ground surface, no columnar structure of free-grown Si ₃ N ₄ is seen at all, and the surface is not as uneven as the sintered surface, and the grain boundaries of the crystal grains are not clear.

Further, as a specific composition of the base material, Si ₃ N ₄ powder containing 50% or more of α-Si ₃ N ₄ as a main component, Al ₂ O ₃ , Y ₂ O ₃ , MgO, Al
N, at least one sintering aid selected from SiO ₂ ,
It is desirable that the mixed powder containing a total of 1 to 50% by weight be sintered. First, when α-Si ₃ N ₄ is 50% or more, the columnar crystal structure of β-Si ₃ N ₄ becomes insufficient and the strength and toughness of the base material are reduced even if sintered under any conditions. To do that. Also, Si ₃ N ₄ is a covalent substance and is known to have poor sinterability. However, Al as a sintering aid
_When at least one of ₂ O ₃ , Y ₂ O ₃ , MgO, AlN, and SiO ₂ , a total of 1 to 50 wt% is mixed, good sinterability is exhibited, and a columnar crystal structure of β-Si ₃ N ₄ It was also found that the promotion of the conversion was promoted.

When the total amount of addition is 50 wt% or more, the strength of the present sintered body itself is reduced.
In addition, as other components other than the sintering aid, various compounds such as carbides, nitrides or carbonitrides of Ti,
Naturally, it is possible to use a hardened substance such as a boride, and / or an additive that improves high-temperature properties such as ZrO ₂ or HfO ₂ . At a sintering temperature of 1600 ° C or lower, grain growth is insufficient, the strength of the sintered body is significantly reduced, and at a temperature of 2,000 ° C or higher, decomposition of Si ₃ N ₄ starts.
600-2000 ° C. Regarding the atmospheric gas, Si ₃ N ₄ is decomposed except for N ₂ gas. Also, 1at
decomposed Si ₃ N ₄ is m or less, also 3000atm above is desirable in an N ₂ gas atmosphere 1~3000atm for industrial practical use is difficult.

If the sintering time is less than 30 minutes, the densification of the crystal grains becomes insufficient, and if the sintering time is more than 5 hours, the crystal grains become coarse and the strength is reduced, so that the range of 30 minutes to 5 hours is good.

When this substrate was sintered under the above sintering conditions, existence of columnar crystals of Si ₃ N ₄ was recognized on the surface of the substrate.

Coating the sintered skin also has an advantage that the manufacturing cost can be reduced by the processing cost used for the grinding finish from an economical viewpoint. The diamond-coated high hardness material thus obtained can be applied to a wide range of throw-away tips, drills, end mills, wear tools, bonding tools and the like.

For throw-away inserts with complex shapes and those requiring high dimensional accuracy, a part or entire surface of the once-sintered insert is ground, and if necessary, a cut-away insert that has been subjected to cutting edge treatment is used. 1300-20
Heat treatment was performed in a temperature range of 00 ° C. in an atmosphere of N ₂ gas and / or an inert gas. The gas pressure range is 1 to 3000at
m. As a result, the entire surface of the chip was heat treated. When the temperature is 1300 ° C or less,
No change in the texture of the ground surface is observed, and when the temperature exceeds 2000 ° C., a decomposition reaction of Si ₃ N ₄ occurs.
Limited to 000 ° C. Regarding the type of atmospheric gas, a decomposition reaction of Si ₃ N ₄ occurs except for N ₂ gas and / or inert gas.

On the ground surface of the present substrate, the presence of columnar crystals of Si ₃ N ₄ was not recognized, but under the above heat treatment conditions, when the present throw-away chip was heat-treated, As in the case of sintered skin, the presence of columnar crystals of Si ₃ N ₄ was recognized.

Further, if necessary for dimensional accuracy, a part of the throw-away tip, which had been entirely heat treated, was ground.

Regarding the heat-treated skin, when the diamond coating layer is formed, it shows a much higher adhesion strength than the ground skin,
In addition, it showed the same adhesive strength as that of the sintered skin. This is because even the heat-treated skin has the same columnar crystal structure as the sintered skin.

In the present invention, it was possible to form a diamond coating layer having high adhesion strength and no thermal residual stress, so that it was possible to provide a layer thickness of 200 μm or more, which is larger than the thickness of a generally used hard coating layer. .

Regarding the layer thickness, if the coating thickness is 0.1 μm or less, no improvement in wear resistance due to the coating layer is observed, and even if a coating layer with a thickness of 200 μm or more is formed, no significant improvement in wear resistance is observed anymore. Since it is uneconomical as an away chip, the range of 0.1 μm to 200 μm is good.

In the present application, the upper surface of the throw-away chip means a rake surface, and the lower surface means a surface facing the upper surface.

 Hereinafter, the embodiment will be described in detail.

〔Example〕

Next, the surface hard member of the present invention will be specifically described with reference to examples.

As a base material, a composition of ceramics based on Si ₃ N ₄ (specifically, Si ₃ N ₄ −4 wt% Al ₂ O ₃ −4 wt% ZrO ₂ −3 wt% Y ₂ O ₃ ) mixed powder at 1800 ° C. and ₅ atm and 1hr sintered in an N ₂ atmosphere gas, the throw-away tip shape SPG422, the material surface, minor 2
[mu] m, columnar crystal structure the Si ₃ N ₄ of length 4μm was observed.

First, in order to compare the sintered surface and the ground surface, the following base material chips were produced. In addition, the schematic diagram of the cutting edge processing of a chip is shown in FIG.

 In the figure, α was 25 °, β was 11 °, and 1 was 0.05 mm.

1.2. Insert with a sintered surface on the whole surface. 3. As an edge treatment, a NL process of 0.05 x 25 mm is applied, and the other portion is a sintered surface. 4. Grinding the upper and lower surfaces and applying the above-mentioned edge treatment to escape. The surface is a chip with a sintered surface. 5. The flank surface is ground and the cutting edge processing is performed as described above, and the upper and lower surfaces are a chip with a sintered surface. Grind the surface and use the 0.05 ×
A tip with a 25 mm NL cutting edge was prepared. At this time, it was confirmed that no columnar crystal structure was present on the ground surface of the throw-away insert. 1700 ℃,
Heat treatment was performed in a 5 atmN ₂ gas atmosphere for 1 hour.

6.7. Insert with heat treated surface on whole surface 8. Grind only the edge-treated surface (hereinafter referred to as NL surface), and insert with heat treated skin on both flank and rake surface 9. Grind and relieve upper and lower surfaces and NL surface Chip with heat-treated skin only on the side 10. Chip with flank and NL surface ground and heat-treated only on upper and lower surfaces 11. Chip with flank, upper and lower surfaces ground and only heat-treated on NL surface 12. Chip with flank ground and heat-treated only upper and lower surfaces, NL surface 13. Chip with upper and lower surfaces ground and heat-treated only flank and NL surface Under these heat treatment conditions, a columnar crystal structure was observed before heat treatment. The short diameter 1.
A columnar crystal structure of Si ₃ N _{4 having} a length of 5 μm and a length of 3 μm was observed.

These cutting tips were heated to 1000 ° C. using a 2.45 GHz microwave plasma CVD apparatus, and kept in a mixed plasma of 2% hydrogen-methane at a total pressure of 80 Torr for 4 to 100 hours to form a diamond coating layer. The diamond throw-away inserts 6-1 of the present invention shown in Table 1 by being formed on the entire upper surface of the insert, near the cutting edge of the flank, and on the NL surface.
3, and comparative chips 1 to 7 were prepared.

In this test, the coating layer deposited on the surface of the substrate was determined by Raman spectroscopy to be 1333 cm ^-1 which is a characteristic of diamond and / or a diamond-like carbon coating layer.
It was confirmed that a peak was shown.

Work material: Al-24wt% Si alloy using these cutting tips Cutting speed: 300m / min. Feeding: 0.1mm / rev. Depth of cut: 0.2mm The amount of flank wear afterwards, the state of wear of the cutting blade, and the state of welding of the work material were observed. Table 2 shows the test results.

〔The invention's effect〕

From the results shown in Table 2, it can be seen that all of the diamond coated throwaway tips 6 to 13 of the present invention have better peeling resistance and wear resistance than the comparative tips 1 to 7.

From this result, when the NL surface and / or the flank were ground surfaces, minute peeling was observed. This also indicates that when the flank face and the NL face are sintered, the adhesion strength of the diamond coating layer to the substrate is considerably high.

Also, diamond-coated indexable tips 1-5
It is also evident that there is no difference in performance between the sintered skin and the heat-treated skin when comparing Nos. 6 and 10.

[Brief description of the drawings]

 FIG. 1 shows an example of the blade edge processing used in the embodiment. α: negative land angle β: clearance angle l: negative land width

Continuation of the front page (56) References JP-A-63-306805 (JP, A) JP-A-2-24005 (JP, A) JP-A-2-48103 (JP, A) JP-A-64-58402 (JP) , A) JP-A-62-251003 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23B 27/14 B23P 15/28

Claims (5)

(57) [Claims] 1. A coating layer of diamond and / or diamond-like carbon deposited from a gas phase on a surface of a throw-away chip base material containing Si ₃ N ₄ as a main component in a thickness of 0.1 to 200 mm.
In the case of a throwaway insert having a layer thickness of μm, a part or all of the surface of the sintered throwaway tip base material is ground, and the heat treatment is applied to the edge of the throwaway insert base material, and the entire surface of the insert is subjected to heat treatment. Characterized in that a diamond or / and diamond-like carbon coating layer is formed on a partial or entire surface of each of a rake face, an edge-treated face, and a flank face of a chip having heat treated skin. Chips. (2) After further grinding a part or all of the heat-treated skin in the preceding paragraph, a diamond or / and / or a rake face, a cutting edge treated face, and a flank face of each of the chips are provided on a part or all of the flank. The diamond-coated indexable insert according to claim 1, wherein a diamond-like carbon coating layer is formed. 3. The diamond-coated indexable insert according to claim 1, wherein a columnar crystal structure of Si ₃ N ₄ is present on the surface of the base material of the diamond chip. Si ₃ N ₄ including wherein alpha-Si ₃ N ₄ 50% or more as a substrate
Powder as a main component, at least one or more sintering aids selected from Al ₂ O ₃ , Y ₂ O ₃ , MgO, AlN, SiO ₂ , 1-50 wt% in total
The mixed powder contained in a temperature range of 1600 to 2000 ° C.
And 30 minutes to 5 hours sintered at an N ₂ gas atmosphere ～3000Atm,
A method of manufacturing a diamond-coated indexable insert, characterized in that at least a flank is a heat-treated surface and at least the flank is coated with diamond. 5. The heat-treated surface has a thickness of 1300 after grinding of the silicon nitride sintered body.
In a temperature range of 2000 ° C., 1 to 3000 atm of N ₂ gas or /
The method according to claim 4, wherein the method is performed in an inert gas atmosphere.