JP2901102B2 - Silicon nitride sintered body for tools and coated silicon nitride sintered body for tools - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a cutting tool such as a turning tool, a milling tool, a drill, an end mill or a slitter,
Bush, wire cutter, guide, nozzle, valve,
The present invention relates to a silicon nitride sintered body for a tool, which is suitable as a tool for wear and corrosion resistance such as a ball, and is particularly suitable for a cutting tool used as a throw-away tip, and a coated silicon nitride sintered body for a tool having a film formed on the surface thereof.

[0002]

2. Description of the Related Art Sintered silicon nitride is excellent in mechanical strength, heat resistance and thermal shock resistance, and has been attempted to be used as a tool material for cutting tools and the like. However,
Since silicon nitride itself has a high affinity for the iron group metal, there is a problem in that when an iron-based material is cut with a cutting tool made of a silicon nitride sintered body, wear resistance is extremely deteriorated, making it impractical.

[0003] In order to solve this problem, there have been many attempts to modify the surface portion of the silicon nitride sintered body or to form a hard coating having poor affinity with iron-based materials on the surface of the silicon nitride sintered body. Are proposed as typical ones of Japanese Patent Application Laid-Open Nos. 2-153865 and 2-27.
No. 5,763, Japanese Unexamined Patent Publication No. Hei 3-8785, Japanese Unexamined Patent Publication No.
No. 6-16665 and Patent Publication No. 60-50224
No. 4 gazette.

[0004]

Problems to be Solved by the Invention
No. 5 and Japanese Patent Application Laid-Open No. 2-275763 teach that a sintered structure of a silicon nitride or sialon sintered body has a composition structure in which the content of Si or the content of silicon nitride or sialon crystal particles is smaller than that of the inside. The body is described.

Japanese Patent Application Laid-Open No. Hei 3-8785 discloses that β
It describes a sintered body in which a surface layer of 10 to 1000 μm of a silicon nitride sintered body has a concentration change such that the zirconium oxide content continuously increases from the inside to the outside and the zirconium nitride content decreases.

[0006] Of these, the sintered body described in the former two publications has a reduced content of Si or silicon nitride or sialon on the surface of the sintered body as compared with the inside. Seems to have solved the problem of affinity with the iron group metal. However, the amount of Si, silicon nitride, and sialon decreased, but the amount of other substances with high affinity with the iron group metal increased. If a problem occurs, and even if this problem can be solved, if a film is formed on the surface of this sintered body for the purpose of further enhancing wear resistance and fracture resistance, the adhesion between the sintered body and the film Since no consideration is given to the properties, there is a problem that the coating is apt to be peeled off.

On the other hand, the sintered body described in the latter publication can increase the strength and toughness by increasing the content of zirconium oxide on the surface of the sintered body. The strength and abrasion resistance at high temperatures are remarkably reduced, and even if a hard coating is formed on the surface of this sintered body in order to enhance the abrasion resistance, the zirconium oxide on the surface of the sintered body adheres to the coating. There is a problem that the properties are hindered and the coating is easily peeled off.

The present invention has solved the above-mentioned problems. More specifically, the present invention comprises a skeleton of a compound containing at least Ti and / or Hf and a matrix mainly containing a silicon nitride sintered body. Silicon nitride for tools with high affinity for iron group metals and high strength and wear resistance at high temperatures by increasing the average elemental content of Ti and / or Hf on the surface of the silicon nitride sintered body An object of the present invention is to provide a sintered body and a coated silicon nitride sintered body for a tool having excellent adhesion of a film.

SUMMARY OF THE INVENTION The present inventors have found that when a work material made of an iron-based material is cut with a conventional cutting tool of a silicon nitride sintered body, the wear resistance and chipping resistance are rapidly increased. When a countermeasure was taken to prevent the film from being lowered and that the film was easily peeled off when a film was formed on the surface of the silicon nitride sintered body, firstly, Ti and / or A sintered body in which a compound containing at least Hf is present and the amount of elements of Ti and / or Hf on the surface of the sintered body is increased is practically used as a cutting tool when an iron-based material is used as a work material. I got the knowledge that I can get it.

Second, when a film made of a compound of Ti and / or Hf is formed on the surface of the silicon nitride sintered body, it is determined that the compound of Ti and / or Hf is present in the silicon nitride sintered body. It has been found that the adhesion between the sintered body and the coating can be improved.

Third, Ti and / or
Or, an excessive content of the Hf compound impairs the strength, heat resistance and thermal shock resistance of the silicon nitride sintered body, but increases the content on the surface of the sintered body and reduces the content inside the sintered body. In addition to solving the problem by reducing the amount, when a film is formed on the surface of the sintered body, it has been found that this enhances the adhesion between the sintered body and the film.

The present invention has been completed based on the first, second, and third findings described above.

[0012] The silicon nitride sintered body for a tool according to the present invention comprises at least 70% by weight of a matrix containing silicon nitride as a main component;
The remainder is a silicon nitride sintered body composed of a skeleton of a compound containing at least Ti and / or Hf, wherein the element amount of Ti and / or Hf in the skeleton is 1 to 20% by weight (the ratio of the whole sintered body) ), And the average element amount of Ti and / or Hf on the surface of the silicon nitride sintered body is reduced to the average element amount of Ti and / or Hf within 200 μm or more from the surface of the silicon nitride sintered body. A silicon nitride sintered body for a tool, wherein the sintered body is increased in comparison with the prior art.

The matrix in the silicon nitride sintered body for a tool according to the present invention includes α-Si ₃ N ₄ (low temperature type) and β-Si
Β sialon (n = 0 to 4.2) and M (S), which are solid solutions of ₃ N ₄ (high temperature type) and Si ₆ —nAlnOn
α-sialon which is a solid solution of i, Al) ₁₂ (O, N) ₁₆ (provided that O <X <Z, M = at least one element of group 2a or 3a of the periodic table) Or more, and the matrix contains at least 70% by weight of the entire sintered body. If this matrix is less than 70% by weight, the skeleton relatively increases to more than 30% by weight, making it difficult to bring out the high hardness and high strength characteristics of silicon nitride itself.

The skeleton in the silicon nitride sintered body for a tool of the present invention is a compound of Ti and / or Hf, specifically, an oxide, nitride, carbide, boride, Ti, Hf of Ti, Hf.
A mixture of one or more of silicides and their mutual solid solutions, or Ti and / or Hf and Zr, V, Nb,
It is composed of oxides, nitrides, carbides, borides, silicides, and mutual solid solutions of at least one of Ta, W, Mo, Cr, Si, Al, and rare earth elements. If the elemental amount of Ti and / or Hf in the skeleton is less than 1% by weight based on the whole sintered body, it becomes difficult to enrich the surface of the sintered body with a compound containing Ti and / or Hf. On the other hand, if the content exceeds 20% by weight, it becomes difficult to obtain a dense sintered body.

One of the features of the present invention is that the surface of the sintered body composed of the matrix and the skeleton has a composition different from that of the inside, specifically, the sintered body is constituted. Of the various types of elements, T on the surface of the sintered body
The average elemental amount of i and / or Hf is 2 from the surface of the sintered body.
It is increased compared to the average elemental amount of Ti and / or Hf in the interior of the metal having a thickness of not less than 00 μm.
% Or more, more preferably Ti
And / or the average elemental amount of Hf is maximum on the surface of the sintered body.

As to the variation of the elements of Ti and / or Hf in the sintered body, for example, firstly, after the maximum at the surface of the sintered body, it continuously decreases toward the inside of the sintered body. And
Secondly, when the average amount of elements inside reaches the maximum, the maximum value is obtained at the surface of the sintered body.
A case may be mentioned in which, after substantially continuing to the inside of 0 μm or less, the amount continuously decreases toward the inside, and reaches the average amount of elements in the inside.

The above-described sintered body of the present invention is used as a base material, and on the surface of the base material, carbides, nitrides, oxides, oxides of Al, oxides of nitrides of Ti, Zr, and Hf, and mutual solid solutions thereof The coated silicon nitride sintered body for a tool of the present invention can be formed by forming at least one kind of a single-layer or multilayer coating.

When the first layer, which is in direct contact with the surface of the substrate, is made of carbides, nitrides, carbonates, nitrides of Ti, Zr, and Hf, and a mutual solid solution thereof, It is preferable from the viewpoint of adhesion, and it is also preferable to use the first layer alone or to use a second layer and a third layer on the surface of the first layer, depending on the application.

The thickness of the coating is preferably 0.5 to 2 μm for the first layer in the case of forming a multilayer, and the total thickness in the case of a single layer or a multilayer is determined by the tool shape, application and composition of the coating. For example, in the case of an application in which an impact force is hardly applied, the total coating thickness is large, for example, about 2 to 10 μm, and an application in which a thermal impact force is applied like a cutting tool,
In particular, when applied to a milling cutting tool, an intermittent cutting tool, or a drill requiring a sharp cutting edge, a total coating thickness of 5 μm or less, more preferably 0.5 to 5 μm.
3 μm.

As a method of producing the silicon nitride sintered body for a tool of the present invention, specifically, a commercially available starting material powder as fine as possible is blended, mixed and pulverized, and then formed into a powder compact. Occasionally, for example, a method of forming by changing the composition components of the inside and the surface, or forming a powder compact with a uniform composition component as in the past, and then sintering the powder containing a compound of Ti and / or Hf And the elements of the powder used for this embedding are penetrated and diffused into the surface of the powder compact, and furthermore, the Ti and / or Ti contained in the powder compact are adjusted by adjusting the pressure and atmosphere during sintering. Alternatively, a method of moving and diffusing a compound of Hf to a surface portion, or a method of combining these can be used.

The formation of a film on the surface of the sintered body can be carried out by a conventional chemical vapor deposition method (CVD method) or physical vapor deposition method (PVD method).

[0022]

The silicon nitride sintered body for a tool according to the present invention has an element content of Ti and / or Hf on the surface of the sintered body that is compatible with a counterpart material, particularly an iron-based material as a work material at the time of cutting. The compound containing Ti and / or Hf acts to improve the strength of the sintered body at a high temperature, and the content distribution of the Ti and / or Hf element on the surface of the sintered body Has an effect of improving the thermal shock resistance of the sintered body.

Further, in the coated silicon nitride sintered body for a tool according to the present invention, the presence of the element of Ti and / or Hf on the surface of the sintered body acts to enhance the adhesion to the coating.

[0024]

Example 1 Commercially available Si ₃ N ₄ powder, Al ₂ O ₃ powder, Y ₂ O ₃ powder, T ₂ powder having an average particle size of 0.5 to 1.5 μm
iC powder, TiN powder, Ti (C, N) powder, TiO ₂
Powder, HfO ₂ powder, and HfN powder were blended in the proportions shown in Table 1, mixed by pulverization in a ball mill, and then press-molded to obtain a powder compact. These powder compacts were embedded in a packing material powder as an element diffusion aid of Ti and / or Hf described in Table 1 and were placed at 1750 ° C. in a nitrogen gas atmosphere.
Sintering at atmospheric pressure for 1000 hours,
Hot isostatic pressure treatment by holding at 0 ° C for 1 hour (HIP treatment)
To obtain silicon nitride sintered bodies No. 1 to 6 of the present invention.

As a comparison, 10 parts were added to the packing material powder at the time of sintering by blending with the composition components of comparative products 1 to 6 shown in Table 1.
Comparative silicon nitride sintered body No. 1 was manufactured by the same manufacturing method as that of the above-described product of the present invention except that 0% Si ₃ N ₄ powder was used.
~ 6.

[0026]

[Table 1] The surfaces of the sintered bodies of the inventive products 1 to 6 and the comparative products 1 to 6 thus obtained and the T from the surface to the inside of 200 μm.
Elemental analysis of i and / or Hf was performed by EPMA (Electron Probe Micro-Analysis), and the results are shown in Table 2.

Next, products 1 to 6 of the present invention and comparative products 1 to 6
, A turning test under the following conditions (A) and a milling test under the conditions (B) were performed, and the results are also shown in Table 2. (A) Dry-type continuous turning test conditions Work material: FC35 Cutting speed: 500 m / min Depth of cut: 1.5 mm Feed: 0.3 mm / rev Cutting time: 2 min Chip shape: SNNM120408 Evaluation: Average flank wear (VB) (B) Milling cutting test conditions by dry method Work material: FCD60 (45H × 200 l) Cutting speed: 150 m / min Depth of cut: 1.5 mm Initial feed: 0.20 mm / rev Chip shape: SNMN120408 Evaluation: Maximum chip breakage Feed (1 Pass
0.03mm / rev feed increase if not lost at

[0028]

[Table 2]

[0029]

Example 2 Using the products 1 to 6 of the present invention and the comparative products 1 to 6 obtained in Example 1, a film was formed on the surface of each sintered body by a CVD method. As for the coating, the layer formed on the surface of the sintered body is the first layer, the next is the second layer, and the next is the third layer,
As shown in Table 3, the coated silicon nitride sintered bodies Nos. 7 to 12 of the present invention and comparative coated silicon nitride sintered bodies Nos. 7 to 12 were formed on the surfaces of the respective sintered bodies.

Using the products 7 to 12 of the present invention and the comparative products 7 to 12 thus obtained, cutting tests were performed under the conditions (A) and (B) of Example 1, and the results are shown in Table 3.

[0031]

[Table 3]

[0032]

The silicon nitride sintered body of the present invention has the same effect of the chipping resistance in the cutting test as compared with the comparative product, and has the effect of improving the abrasion resistance by about 45 to 62%.

Further, the coated silicon nitride sintered body of the present invention
Compared with the comparative coated silicon nitride sintered body, the abrasion resistance in the cutting test is improved by about 43 to 97%, and the fracture resistance is about 39%.
There is a remarkable effect of improving by ~ 52%.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-208182 (JP, A) JP-A-53-55312 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C04B 35/584 B23P 15/28 C04B 41/87

Claims (6)

(57) [Claims] 1. A silicon nitride sintered body comprising at least 70% by weight of a matrix containing silicon nitride as a main component and a skeleton of a compound containing at least Ti and / or Hf, wherein Ti and / or The elemental amount of Hf is 1 to 20% by weight (ratio of the whole sintered body), and Ti and / or Hf on the surface of the silicon nitride sintered body
Is 200 from the surface of the silicon nitride sintered body.
A silicon nitride sintered body for a tool, wherein the silicon nitride sintered body for a tool has an increase in the average elemental content of Ti and / or Hf in the interior of not less than μm. 2. The T on the surface of the silicon nitride sintered body
The average elemental amount of i and / or Hf is increased by 5% or more with respect to the average elemental amount of Ti and / or Hf within 200 μm or more from the surface of the silicon nitride sintered body. The silicon nitride sintered body for a tool according to claim 1. 3. A silicon nitride sintered body comprising at least 70% by weight of a matrix containing silicon nitride as a main component and a skeleton of a compound containing at least Ti and / or Hf, wherein Ti and / or The elemental amount of Hf is 1 to 20% by weight (ratio of the whole sintered body), and Ti and / or Hf on the surface of the silicon nitride sintered body
A silicon nitride sintered body for a tool, characterized in that the average element amount of the above is maximum on the surface of the silicon nitride sintered body. 4. The method according to claim 1, wherein the silicon nitride sintered body has a surface of Ti, Zr, Hf carbide, nitride, oxide, A
(1) a coated silicon nitride sintered body for a tool, wherein a coating comprising at least one kind of a single layer or a multilayer of oxides, nitride oxides and mutual solid solutions thereof is formed. 5. The silicon nitride sintered body according to claim 2, wherein Ti, Zr, Hf carbide, nitride, oxide, A
(1) a coated silicon nitride sintered body for a tool, wherein a coating comprising at least one kind of a single layer or a multilayer of oxides, nitride oxides and mutual solid solutions thereof is formed. 6. The silicon nitride sintered body according to claim 3, wherein Ti, Zr, Hf carbide, nitride, oxide, A
(1) a coated silicon nitride sintered body for a tool, wherein a coating comprising at least one kind of a single layer or a multilayer of oxides, nitride oxides and mutual solid solutions thereof is formed.