JPH10212183A - Surface coated silicon nitride tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface coated silicon nitride tool which obviates the occurrence of trouble, such as peeling of layers by preventing the generation of internal stresses by heat. SOLUTION: A chip is obtd. by forming coating layers 5 having a thickness in a range of 2 to 8μm over the entire part of the surface of a base body 3. The compsn. of the base body 3 consists of 95wt.% Si3 N4 , 1.5wt.% Al2 O3 , 1wt.% MgO and 1.5wt.% Yb2 O and the crystal grain size thereof is <=0.5μm in average. The coating layers 5 comprise a base body side layer 11 which consists of AlON and is disposed to cover the surface of the base body 3, an intermediate first inside layer 12 which consists of TiC and is disposed to cover the surface of the base body side layer 11', an intermediate second inside layer 13 which consists of TiCN and is disposed to cover the surface of this intermediate first inside layer 12 and the outermost layer 14 which consists of TiN and is disposed to cover the surface of this intermediate second inside layer. The intermediate first inside layer 12 and the intermediate second inside layer 13 constitute the intermediate layer 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-coated silicon nitride tool used for tools such as indexable inserts, end mills and drills.

[0002]

2. Description of the Related Art Conventionally, as a tool such as a throw-away tip (hereinafter simply referred to as a tip) or a drill, a ceramic having a plurality of coating layers such as Al ₂ O ₃ or TiC provided on the surface of a substrate made of silicon nitride. Tools are known (for example, Japanese Patent Publication No. 3-49681, Japanese Patent Publication No. 63-127).
No. 8, JP-A-6-246511, JP-B-59
-13475).

[0003]

Although this coating layer is provided for the purpose of improving abrasion resistance and heat resistance, the above-mentioned prior art sufficiently eliminates internal strain caused by residual stress due to heat. There was a problem that it was not possible.

That is, this type of ceramic tool has a high temperature at the time of manufacture or use. Therefore, the difference in the coefficient of thermal expansion between the layers constituting the coating layer or the difference between the coefficient of thermal expansion between the silicon nitride substrate and each layer. Due to this, a large residual stress may be applied to each layer, particularly when the temperature changes from a high temperature state to a normal temperature state, which may cause internal strain. When the internal strain is large, there is a problem that a problem such as peeling of the layer may occur in some cases.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a surface-coated silicon nitride tool which prevents generation of internal strain due to heat and does not cause problems such as delamination. Aim.

[0006]

Means for Solving the Problems In order to solve the above problems, the invention of claim 1 is directed to a surface-coated silicon nitride tool having a coating layer on the surface of a substrate containing silicon nitride as a main component.
The coating layer includes a base-side layer made of AlON provided on the surface of the base, an intermediate layer provided on the surface of the base-side layer, and an outermost layer made of TiN provided on the surface of the intermediate layer. And the thickness of the coating layer is 2
-8 μm, and the intermediate layer is made of AlON, TiC, T
The gist of the present invention is a surface-coated silicon nitride tool comprising at least one intermediate inner layer selected from iN and TiCN.

The intermediate layer is made of AlON, TiC, T
It consists of one or more intermediate inner layers selected from iN and TiCN, and the selection is made so that the coating layer has three different layers. That is, for example, only the AlON1 layer or the TiN1
When only the layer is selected, for example, the intermediate layer and the substrate side layer or the outermost layer are integrated, and the three-layer coating layer required for the present invention is not formed. Cases are excluded. Therefore, when the intermediate inner layer is one layer, AlON-TiC-TiN, AlON-TiCN-
Although limited to the case of TiN, there is no such limitation in the case of a plurality of layers.

The invention according to claim 2 is characterized in that AlON constituting the substrate side layer has an average crystal grain size of 0.5 μm or less, and the thickness of the substrate side layer is 1 μm or less. The gist of the invention is a surface-coated silicon nitride tool according to claim 1.

According to a third aspect of the present invention, the silicon nitride constituting the substrate has an average crystal grain size of 0.5 μm or less, and the sintering aid component contained in the substrate is 2 to 5% by weight. The gist is the surface-coated silicon nitride tool according to claim 1 or 2, characterized by the following.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the surface-coated silicon nitride tool according to the first aspect of the present invention, the coating layer is formed on the surface of the substrate by the A
It has three types of layers: a substrate side layer made of 1ON, an intermediate layer provided on the surface of the substrate side layer, and an outermost layer made of TiN provided on the surface of the intermediate layer.

The above-mentioned coating layer is a so-called hard coating layer used for the purpose of improving the wear resistance of the tool, etc., and in the present invention, its thickness is set to 2 to 8 μm. In other words, if the thickness is smaller than this thickness, the coating layer will be worn out in a short time, and the progress of abrasion during cutting or the like will be large. On the other hand, if the thickness is larger than that, the coating layer will be easily peeled off. It is suitable in terms of abrasion and prevention of peeling.

In the coating layer, the substrate-side layer uses AlON instead of the conventional Al ₂ O _3.
As shown in Table 1 below, ON has a coefficient of thermal expansion close to that of silicon nitride as a base material (base material), and thus hardly causes peeling even when rapidly heated or cooled. In addition, since AlON has a high thermal conductivity, it has a good heat pull and hardly generates a thermal crack.
Furthermore, since AlON forms a solid solution with the substrate containing silicon nitride as a main component, it has a high affinity with the substrate and good adhesion.

Further, the outermost layer is made of TiN.
Since the layer made of N has a small coefficient of friction, the frictional resistance with the material to be cut is reduced, thereby suppressing the generation of heat generated at the cutting edge of a chip or the like during processing. In particular, the intermediate layer is made of AlO
It comprises one or more intermediate inner layers selected from N, TiC, TiN, and TiCN, and these intermediate inner layers have a coefficient of thermal expansion (or the same) between the substrate side layer and the outermost layer. (A degree of thermal expansion coefficient), the residual stress due to heat can be reduced, and the internal distortion is hardly generated.

That is, the thermal expansion coefficients of the respective materials are shown in Table 1 below. By providing an intermediate inner layer having the following thermal expansion coefficient between the substrate side layer and the outermost layer, the material can be manufactured and used. Even when a large force is applied between adjacent layers due to a large temperature change, the residual stress is relaxed and internal strain is less likely to occur. Therefore, peeling of the layer hardly occurs at the time of manufacture or use, and it is excellent in terms of yield, durability and the like.

[0015]

[Table 1]

The thickness of each intermediate inner layer constituting the intermediate layer may be, for example, in the range of 0.3 to 1.5 μm. At the time of use or during use, peeling hardly occurs. Claim 2
According to the invention, the crystal grain size of AlON constituting the substrate side layer is 0.5 μm or less on average, and the thickness is 1 μm or less.

AlON is a material having excellent adhesion (adhesion) to silicon nitride, which is the main component of the substrate, and has a crystal structure of a mixture of columnar crystals and particulate crystals. . Therefore, the average of the crystal grain size is an average of the diameter of the columnar crystal and the diameter of the particulate crystal.

Here, if the average size of the crystal grains exceeds 0.5 μm, the average crystal grain size is preferably 0.5 μm or less, because the crystal grains are too large and the crystals easily fall off when a tool is used. Further, if the base layer is too thick, the coating layer itself is easily peeled off from the base similarly, so that the thickness of the base layer is preferably 1 μm or less. That is, the thickness of the substrate side layer is preferably smaller than twice the average of the crystal grain size.

According to the third aspect of the present invention, the crystal grain size of silicon nitride constituting the substrate is 0.5 μm or less on average, and the sintering aid component contained in the substrate is 2 to 5% by weight. If the crystal grain size of silicon nitride is 0.5 μm or less on average, the strength becomes high and it becomes difficult to chip during cutting or the like. In addition, when the sintering aid is 2
When the content is within the range of 5 to 5% by weight, the hardness is increased and the wear resistance is improved.

Particularly, when the sintering aid has a content of 2 to 5% by weight, the performance of the boundary wear is twice as high as that of the conventional one. The surface wear is small and the service life can be further extended. The intermediate layer is made of AlON, TiC, TiN,
When a plurality of sets of two or more intermediate inner layers selected from TiCN and TiCN are stacked, the ability to further reduce the residual stress is preferably high.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, as an embodiment of the surface-coated silicon nitride tool of the present invention, a throw-away tip (hereinafter referred to as a tip) will be described.
Will be described as an example. a) As shown in FIG. 1, the chip 1 of the present embodiment has a substantially rectangular parallelepiped shape, and a coating layer 5 having a thickness of 2 to 8 μm is formed on the entire surface of a substantially rectangular parallelepiped substrate 3 made of Si ₃ N _4. Is formed.

A portion corresponding to the cutting edges 1a and 1b of the base 3 of the chip 1 is subjected to chamfering of 0.2 mm × 25 degrees, whereby the chamfered portion is formed on the cutting edge 1a of the chip 1. Is formed. The tip 1 is usually fixed to a corner of the holder 7 using a fixture (not shown) or the like and used for cutting.

The composition of the substrate (base material) 3 is Si ₃ N ₄ ;
96% by weight, Al ₂ O ₃ ; 1.5% by weight, MgO: 1% by weight, Yb ₂ O ₃ : 1.5% by weight, and the average crystal grain size is 0.5 μm or less (for example, 0.3 μm). It is. Also,
As shown in FIG. 2, the coating layer 5 is a 1 μm-thick substrate side layer 11 made of AlON provided over the surface of the substrate 3.
An intermediate first inner layer 12 made of TiC and covering the surface of the base layer 11 and having a thickness of 0.3 μm;
An intermediate second internal layer 13 of 0.3 μm in thickness made of TiCN provided over the surface of the internal layer 12 and a thickness 0.4 of TiN provided over the surface of the intermediate second internal layer.
and an outermost layer 14 of μm. In addition, intermediate 1
The intermediate layer 15 is constituted by the internal layer 12 and the intermediate second internal layer 13.

B) Next, a method of manufacturing the chip 1 of the present embodiment will be described. First, a method for manufacturing the base material 3 will be described. S is the main component
Al ₂ O ₃ powder and Mg as sintering aids for i ₃ N ₄ powder
The O powder and the Yb ₂ O ₃ powder are blended so as to have the above-mentioned weight%, and mixed with an alcohol in a wet ball mill.

Next, after drying, paraffin is used as a pressing aid.
1 ton / cm^TwoCold pressure at above pressure
By pressing, a molded body to be the base material 3 is obtained. Next
The molded body is_TwoIn a gas atmosphere, for example, 15
Bake at a temperature of 50 to 1900 ° C for 10 to 120 minutes
By forming, a fired body having substantially the same shape as the base 3 is obtained.
obtain. Also, if necessary, 1600 ° C. × 2 hours, 15
00 atm (N _TwoGas) to perform HIP processing.

Then, the fired body thus obtained is
In the ISO standard, it is polished to the shape of SNGN120412,
After washing, the base 3 having the above-described shape is completed. The Si ₃ N ₄ raw material powder which is the main component of the base 3 is usually desirably α-type, and preferably has a particle size of 1 μm or less.

Next, a method of forming the coating layer 5 will be described. The substrate 3 manufactured by the manufacturing method described above is
It is set in a known CVD apparatus. This CVD device is
The coating layer 5 is formed by a chemical vapor deposition method (so-called CVD method).
Is formed.

Then, by utilizing the reactions shown in the following reaction formulas (1) to (4), the substrate side layer 11 made of AlON
Each layer is sequentially formed in the order of the intermediate first internal layer 12 made of TiC, the intermediate second internal layer 13 made of TiCN, and the outermost layer 14 made of TiN. [AlON] AlCl ₃ + 3 / 2H ₂ + CO ₂ + 1 / 2N ₂ → AlON + 3HCl + CO (1) [TiC] TiCl ₄ + CH ₄ → TiC + 4HCl (2) [TiCN] TiCl ₄ + xCH ₄ + (1-x) / 2N ₂ +2 (1-x) H ₂ → Ti (C _x N _{1 -x} ) + 4HCl (3) [TiN] TiCl ₄ + 2H ₂ + 1 / 2N ₂ → TiN + 4HCl (4) Thus, as shown in FIG. On the surface of the base 3, a three-layer structure composed of the base side layer 11, the intermediate layer 15, and the outermost layer 14 described above (in consideration of the two intermediate inner layers 12 and 13,
The chip 1 including the coating layer 5 having a (layer structure) is completed.

C) Next, an experimental example performed to confirm the effect of the present embodiment will be described. In this experimental example, a chip having a coating layer having a layer structure shown in Tables 2 and 3 below was manufactured.
Cutting (dry cutting) was performed under the following experimental conditions, and the flank wear and (pre-clearance) boundary wear in that case were measured. The results are shown in Tables 2 and 3 below.

Further, the average value of the crystal grain size of the substrate side layer made of AlON was examined using an electron microscope. The results described above are also shown in Tables 2 and 3. Here, flank wear is
Assuming that the upper right side of FIG. 3 is the cutting edge 1a in contact with the work material,
This means wear occurring below the cutting edge 1a, and the length in the vertical direction is the flank wear amount. Further, (front escape) boundary wear means fang-like wear that occurs below the cutting edge 1b, which is the upper left side of the figure, and the length of the fangs in the vertical direction is the (front escape) boundary wear amount. is there.

The tip shape is the same as that of the above embodiment.
NGN120412, chamfering is also 0.2mm x 25
Degree chip. (Experimental conditions) Work material: JIS FC200 (normal cast iron) Cutting speed: 100 m / min Feed speed: 0.1 mm / rev Cutting depth: 1.0 mm Cutting time: 60 min

[0032]

[Table 2]

[0033]

[Table 3]

In Tables 2 and 3, "times" means that the same layer structure is laminated by the number of layers. As is clear from Tables 2 and 3, the chips 1 of the samples Nos. 1 to 14 of the examples, which are the scope of the present invention, have defects such as peeling, chipping and cracking in the coating layer 5 during manufacture and use. No processing occurred and processing could be suitably performed. Further, those in the range of the present invention are preferable because the flank wear amount is 0.23 mm or less and the boundary wear amount is 0.26 mm or less, which is excellent in wear resistance and has a long life.

Samples 1 to 7, 11, 1 and 1 having an average crystal grain size of the substrate-side layer 11 made of AlON of 0.5 μm or less and having a thickness of 1 μm or less are particularly preferred.
The chips Nos. 3 and 14 are desirable because they have a small amount of flank wear and boundary wear as a whole, and are more excellent in wear resistance.

In addition, comparing Sample No. 3 and Sample No. 4 (or Sample No. 13 and Sample No. 14) of the embodiment,
It can be seen that the flank wear and the boundary wear increase as the total film thickness increases, and that the larger the thickness increases, the more the film tends to peel. On the other hand, among the comparative examples out of the scope of the present invention, the chip of sample No. 16 is not preferable because the coating layer is peeled off at the time of manufacture and cannot be properly processed. Sample No. 1
The chips 8 and 19 are not preferred because the coating layer is peeled off or damaged during use. Furthermore, Sample Nos.
The chips of Nos. 7 and 20 did not cause peeling or chipping of the coating layer during production or use, but had a flank wear of 0.27 mm.
As described above, the boundary wear is as large as 0.26 mm or more, and the wear resistance is poor, and the life is short.

As is clear from this experimental example, the chip 1 of the present embodiment having the coating layer 5 having the above-mentioned layer structure on the surface of the base 3 is excellent in the ability to alleviate the residual stress. And a remarkable effect that the coating layer 5 is hardly peeled off during use. In addition, since the thickness of the coating layer 5 is appropriately set, the coating layer 5 has excellent wear resistance and can achieve a long life.

The AlON of the substrate side layer 11 is made of Al ₂
Since the thermal conductivity is higher than that of O ₃ , the heat removal is good and the heat crack is hardly generated. Furthermore, the TiN of the outermost layer 14 has the advantage that the generation of heat generated at the cutting edge of the chip 1 at the time of processing can be suppressed, whereby higher speed processing and higher efficiency processing can be performed.

It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that the present invention can be carried out in various modes without departing from the gist of the present embodiment. For example, in the above-described embodiment, a chip is taken as an example of application of the present invention. However, if the above-described configuration is adopted for another surface-coated silicon nitride tool such as a drill, the same effect can be obtained.

The combination of the intermediate inner layer constituting the intermediate layer is not limited to the combination shown in the above-described experimental example.
Various configurations are possible. Further, in the present invention, the substrate mainly containing silicon nitride is not limited to the substrate mainly containing Si ₃ N ₄ ,
Substrates containing sialon as a main component having similar properties are also included.

Even if a layer made of a material outside the scope of the present invention is disposed between the internal intermediate layers, the present invention is within the scope of the present invention as long as the functions and effects of the present invention can be obtained. That is, even when a layer made of another material is formed, the case of including the above-described configuration of the present invention is included in the scope of the right of the present invention.

[0042]

As described in detail above, the surface-coated silicon nitride tool according to the first aspect of the present invention hardly causes peeling of the coating layer during production or use. Also, it has excellent wear resistance and long life.

According to the second aspect of the present invention, the AlON
According to the setting of the crystal grain size and the thickness thereof, the crystal hardly falls off when the tool is used, and the layer is hardly peeled off, which is more preferable. According to the third aspect of the present invention, by setting the crystal grain size of the silicon nitride of the base and the sintering aid component, the strength is further increased, and it is hard to be chipped at the time of cutting or the like, and the hardness is increased to improve the wear resistance. .

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a chip of the present embodiment with a part cut away.

FIG. 2 is an explanatory diagram showing a cross section of a coating layer and the like of the chip of the present embodiment.

FIG. 3 is an explanatory view showing a state of wear of the tip of the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Tip 1a, 1b ... Blade edge 3 ... Base 5 ... Coating layer 7 ... Holder 11 ... Base side layer 12 ... Intermediate 1st inner layer 13 ... Intermediate 2nd inner layer 14 ... Outermost layer 15 ... Intermediate layer

Claims (3)

[Claims] 1. A surface-coated silicon nitride tool having a coating layer on the surface of a substrate containing silicon nitride as a main component, wherein the coating layer comprises: a substrate-side layer made of AlON provided on the surface of the substrate; An intermediate layer provided on the surface of the side layer; and an outermost layer made of TiN provided on the surface of the intermediate layer.
８8 μm, and the intermediate layer is made of AlON, TiC, TiN, and TiC
A surface-coated silicon nitride tool comprising at least one intermediate inner layer selected from N. 2. The substrate according to claim 1, wherein the AlON constituting the substrate-side layer has an average crystal grain size of 0.5 μm or less, and the thickness of the substrate-side layer is 1 μm or less. Surface coated silicon nitride tool. 3. The method according to claim 1, wherein the silicon nitride constituting the base has a crystal grain diameter of 0.5 μm or less on average, and the sintering aid component contained in the base is 2 to 5% by weight. The surface-coated silicon nitride tool according to claim 1.