JP3107168B2 - Coated silicon nitride sintered body for tools - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to cutting tools such as turning tools, milling tools, drills and end mills, wear-resistant tools such as cutting blades, cutting blades, and mold tools, and corrosion-resistant tools such as valves, nozzles, and mechanical seals. The present invention relates to a coated silicon nitride sintered body for a tool, which is suitable for a lubricating tool such as a bearing ball and the like, and particularly, is most suitable as a cutting tool for cutting cast iron.

[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 such as a cutting tool. However, since silicon nitride is rich in affinity with iron group metals, when cutting iron-based materials with a cutting tool of silicon nitride sintered body,
There is a problem that the wear resistance is extremely deteriorated and cannot be used practically.

[0003] In order to solve this problem, there have been many proposals for coated silicon nitride sintered bodies in which a hard coating having poor affinity for iron group metals is formed on the surface of the silicon nitride sintered body. As a representative example, JP-A-56-16665
JP, JP-A-56-155080, JP-A-57-155080
JP-A-16162, JP-A-58-74585 and JP-A-60-502244.

[0004]

Problems to be Solved by the Invention JP-A-56-1666
No. 5, JP-A-56-155080 and JP-A-57-16162 disclose titanium carbide, titanium nitride, titanium carbonitride, and titanium nitride as a base material of a silicon nitride sintered body containing silicon nitride as a main component. A coated sintered body for a cutting tool which can form at least one kind of a single layer or a multilayer of titanium carbonate and titanium carbonitride and an outer layer of aluminum oxide is described.

[0005] In the coated sintered bodies described in these publications, the composition of the base material has not been studied in consideration of the compatibility between the base material and the coating, and silicon nitride itself, which is the main component of the base material, has not been studied. Since it is a compound with high covalent bonding properties, the adhesion between the substrate and the inner layer is poor, the coating easily peels off, and the wear resistance and chipping resistance are almost the same as those of the conventional silicon nitride sintered body. There is a problem that can only be obtained.

Japanese Patent Application Laid-Open No. 58-74585 discloses that a silicon nitride sintered body composed of 1 to 30% by weight selected from yttrium oxide, aluminum nitride, and hafnium oxide and the remainder consisting of silicon nitride is coated with silicon carbide. And / or a coated silicon nitride sintered body for high-speed cutting in which an inner layer of silicon oxide and an outer layer of aluminum oxide are formed.

[0007] The coated silicon nitride sintered body described in the publication is
Although the composition of the base material is selected, the compatibility between the base material and the inner layer and between the inner layer and the outer layer is not considered.Especially, for the inner layer of silicon carbide, silicon carbide itself is a compound having a high covalent bond. Because of this, the adhesion between the base material and the inner layer and between the inner layer and the outer layer is poor, and there is a problem that the effects are almost the same as those of the above three publications.

In Japanese Patent Publication No. 60-502244, yttrium oxide, aluminum oxide, and hafnium oxide are selected, and a titanium nitride and aluminum oxide film is selected as a base material of a sintered body composed of silicon nitride with the balance being silicon nitride. A coated silicon nitride sintered body that can be formed by heating is described.

The coated silicon nitride sintered body described in the publication is
When aluminum oxide is selected as the base material, it is preferable because it has the effect of promoting the sinterability of the base material itself, but the strength is reduced at high temperatures and the adhesion strength between the base material and the coating film is low, so that the wear resistance and the fracture resistance There is a problem that the effect on sex is small.

The present invention has solved the above-mentioned problems. Specifically, the present invention maximizes the effects of aluminum nitride and a hafnium compound as constituent components of a base material.
An object of the present invention is to provide a coated silicon nitride sintered body having high wear resistance and chipping resistance which is practically used as a tool by constructing an optimum coating composition for the composition of the base material.

[0011]

Means for Solving the Problems The present inventors have found that when a work material made of an iron-based material is cut with a conventional cutting tool made of a coated silicon nitride sintered body, the wear resistance and the chipping resistance are sharply increased. In order to solve the problem of reduced resistance, we examined the relationship between the base material and the coating of the sintered body. First, when coated silicon nitride was used as a cutting tool, the abrasion resistance and fracture resistance were reduced. It has been found that the main cause of the rapid decrease is peeling of the coating.

Second, it has been found that when a titanium compound film is formed on the surface of a silicon nitride sintered body containing aluminum nitride and a hafnium compound, the adhesion between the substrate and the film is significantly improved. Was.

The present invention has been completed based on the first and second findings.

The coated silicon nitride sintered body for a tool according to the present invention comprises:
What is claimed is: 1. A coated silicon nitride sintered body obtained by coating a hard coating on the surface of a base material of a sintered body containing silicon nitride as a main component, wherein the base material is a rare earth element oxide, oxynitride, or a mutual solid solution thereof. 1 to 8% by weight of a compound of at least one rare earth element, and 1 to 8% by weight of aluminum nitride or 2% by weight
An aluminum compound obtained by combining 2 to 10% by weight of aluminum nitride with the following aluminum oxide; and 1 to 8% by weight of at least one hafnium compound among hafnium oxide, hafnium oxynitride, hafnium oxycarbide, and hafnium oxynitride carbide. And the remainder is a sintered body of silicon nitride, and the hard coating is a single layer or a multilayer of titanium nitride, titanium carbide, titanium oxynitride, titanium oxycarbide, titanium oxycarbide, and titanium oxycarbide. It is characterized by comprising an inner layer having an average layer thickness of 0.1 to 3.0 μm and an outer layer having an average layer thickness of 0.1 to 3.0 μm, which is a single layer or a multilayer of aluminum oxide or aluminum oxynitride. .

When the content of the rare earth element compound in the substrate is less than 1% by weight, the effect of promoting sintering when sintering the substrate itself is weak, and a dense sintered body is obtained. , And the mechanical strength and toughness of the sintered body at room temperature decrease. Conversely, if the amount exceeds 8% by weight, the mechanical strength and thermal shock resistance of the sintered body at high temperatures decrease. Become noticeable. The compound of the rare earth element is specifically composed of oxides, oxynitrides of Sc, Y, and lanthanoids and a mutual solid solution thereof, particularly yttrium oxide,
Dysprosium oxide is preferable, and the content is also preferably 2 to 6% by weight.

When the aluminum compound contained in the base material is made of aluminum nitride alone, if the amount is less than 1% by weight, the strength and fracture resistance at high temperatures are reduced. Mechanical strength and toughness decrease. Further, in the case of an aluminum compound comprising a combination of aluminum oxide and aluminum nitride which has an effect of promoting sintering of the base material, a glass phase is easily formed and the strength at high temperatures is reduced, so that 2% by weight
The following aluminum oxide is used, and 2 to 10% by weight to supplement the strength reduction at high temperature due to aluminum oxide
Of aluminum nitride.

When the content of the hafnium compound in the substrate is less than 1% by weight, the adhesion between the inner layer coating and the substrate is reduced, and the strength of the substrate itself at high temperatures is reduced. When the amount exceeds the above range, the mechanical strength at room temperature decreases and the thermal shock resistance decreases. When the hafnium compound is made of hafnium oxide, it is preferable because fracture resistance as a cutting tool is remarkably enhanced.
It is preferable that the content is 〜7% by weight.

The silicon nitride contained in the base material is a low-temperature α
-Si ₃ N ₄ , high-temperature β-Si ₃ N ₄ , and other compounds described above exist as low-temperature α-sialon or high-temperature β-sialon with elements of aluminum, oxygen and nitrogen interposed. May be the case. In particular, in the case of a base material mainly composed of β-Si ₃ N _{4 and} having a crystal structure in which β sialon is present at an almost unidentifiable grain boundary, the strength and stability at high temperatures are high. preferable.

The inner layer as a coating has an average thickness of 0.1 μm.
m, the adhesion between the inner layer and the outer layer is reduced,
Conversely, when the thickness exceeds 3.0 μm, the number of cracks generated in the inner layer increases, and peeling in the inner layer occurs frequently. Therefore, the average layer thickness is determined to be 0.1 to 3.0 μm. In particular, it is preferable that the average layer thickness of the inner layer be 0.4 to 2.5 μm in consideration of the adhesion between the inner layer and the outer layer and the strength in the inner layer.

The outer layer as a coating has an average layer thickness of 0.1 μm.
m, the abrasion resistance is reduced.
When the thickness exceeds m, peeling in the outer layer or minute chipping is apt to occur frequently, so the average layer thickness is 0.1 to 3.0 μm.
It is defined. In particular, the average thickness of the outer layer is preferably 0.3 to 2.5 μm from the viewpoint of abrasion resistance or prevention of peeling in the outer layer. When this outer layer is made of aluminum oxide, there is no particular restriction on its crystal structure, but κ
-Aluminum oxide is preferred because it forms an outer layer of fine grains and significantly improves wear resistance and fracture resistance as a cutting tool.

When the outermost layer is formed on the surface of the outer layer, if necessary, the outermost layer is colored such as pale yellow, golden or yellow-brown, so that a cutting tool such as a throw-away tip is particularly used as a tool. When used as a tool, it is preferable because the edge of the blade before and after use becomes easy and the wear resistance is further remarkably improved. When it is necessary to increase both the wear resistance and the identification of the cutting edge before and after use, the thickness of the outermost layer is 0.2
It is preferable that the thickness of the outermost layer be 0.02 μm.
What is necessary is just 5 micrometers or more.

When producing the coated silicon nitride sintered body for a tool of the present invention, a base material is prepared by applying a conventional powder metallurgy method or a method for producing a ceramic sintered body, and the base material is formed by a conventional method. For example, it can be obtained by forming a coating by a chemical vapor deposition method (CVD method) or a physical vapor deposition method (PVD method).

[0023]

The coated silicon nitride sintered body for a tool according to the present invention has an effect of increasing the strength of a base material at a high temperature by the ratio of both an aluminum compound and a hafnium compound constituting the base material. More remains on the surface than the inside and contributes to the strengthening of the adhesion to the inner layer of the coating, and the rare earth element compound and the aluminum compound, mainly the rare earth element compound, contribute to the sintering promoting action of the base material. Of the coatings, the inner layer acts as a mediator of the adhesion between the base material and the outer layer, and the structure of the inner layer and the outer layer or the inner layer, the outer layer, and the outermost layer increases the wear resistance and chipping resistance as a cutting tool. Is what you are doing.

[0024]

Example 1 Si ₃ N ₄ powder having an average particle size of 0.7 μm, HfO ₂ , Hf (O, C), Hf having an average particle size of 1.5 μm
(O, N) powder, Y ₂ O ₃ , Al having an average particle size of 0.5 μm
Each of N and Al ₂ O ₃ powders was blended in the proportions shown in Table 1, and the mixture was pulverized and mixed by a ball mill and press-formed. Then, after sintering the compact at 1750 ° C. for 1 hour under a normal pressure in a nitrogen gas atmosphere, the compact was heated to 1700 ° C. in a nitrogen gas at 1000 atm.
, A hot isostatic pressure treatment (HIP treatment) by holding for 1 hour was performed to obtain each sintered body. The sintered body thus obtained was ground to obtain a base material of a throw-away chip having an SNGN120408 shape according to ISO standard.

These substrates are placed in a CVD reactor,
A mixed gas of AlCl ₃ , CO and H ₂ obtained by a reaction between Al and HCl after a treatment at 940 ° C. in a mixed gas of TiCl ₄ , N ₂ and H ₂ to form an inner layer of a 1 μm thick TiN film Medium, 940 ° C., 1.5 μm thick κ-Al ₂
The outer layer of the O ₃ film is formed to produce products 1 to 7 of the present invention and comparative products 1 to
6 was obtained.

Using the products 1 to 7 of the present invention and the comparative products 1 to 6, cutting tests were carried out under the following conditions (A) and (B), and the results are shown in Table 1.

(A) Continuous turning test under dry conditions of conditions Work material: FC35 Cutting speed: 500 m / min Depth of cut: 1.5 mm Feed: 0.3 mm / rev Cutting time: 2 min Evaluation: Average flank wear (B) conditions, milling tests with a dry (V _B) workpiece: FCD60 (45 × 200mm square bars) cutting speed: 150 meters / min cut: 1.5 mm initial feed: 0.20 mm / rev Rating: feed maximum defect or chipping occurs (If there is no chipping or chipping, feed 0.03mm
/ Rev increases.

[0028]

[Table 1]

[0029]

Example 2 Using the powder of Example 1, 88% Si ₃ N ₄
A powdered composition of 4% HfO ₂ -4% Y ₂ O ₃ -4% AlN (% by weight) was prepared, and a base material of a sintered body was prepared in the same manner as in Example 1. Then, TiCl ₄ , AlCl ₃ ,
In a mixed gas selected from N ₂ , CH ₄ , CO, CO ₂ , and H ₂ gases, the mixture is treated at 940 to 1100 ° C. to form a coating having the composition shown in Table 2 on the surface of the base material, and Invention 8 ~
16 and comparative products 7 to 10 were obtained.

Using the products 8 to 16 of the present invention and the comparative products 7 to 10 thus obtained, cutting tests were performed under the conditions (A) and (B) of Example 1, and the results are also shown in Table 2.

[0031]

[Table 2]

[0032]

The coated silicon nitride sintered body for a tool according to the present invention is different from a conventional silicon nitride sintered body (comparative product 1).
It has the effect of having 1.8 to 1.9 times the wear resistance and 1.6 to 1.9 times the fracture resistance, and is equivalent to 1 to 1 compared with the comparative product which is not the sintered body of the present invention. It has the effect of having 0.8 times the wear resistance and 1.1 to 1.9 times the fracture resistance, and has the effect of being excellent in the adhesion between the base material and the film and the peeling resistance of the film.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-224202 (JP, A) JP-A-58-208182 (JP, A) JP-A-61-101482 (JP, A) JP-A-61-182 191584 (JP, A) JP-A-63-89461 (JP, A) JP-A-58-74574 (JP, A) JP-A-4-124075 (JP, A) JP-A-4-240162 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 35/58 C04B 41/89 B23P 15/28

Claims (2)

(57) [Claims] 1. A coated silicon nitride sintered body obtained by coating a hard coating on the surface of a base material of a sintered body containing silicon nitride as a main component, wherein the base material is a rare earth element oxide, oxynitride or Compound 1 of at least one rare earth element in a mutual solid solution of
-8% by weight and 1-8% by weight of aluminum nitride or 2
An aluminum compound obtained by combining aluminum oxide of 2% by weight or less with aluminum oxide of 2% by weight or less, hafnium oxide, hafnium oxynitride, hafnium oxycarbide,
A sintered body comprising 1 to 8% by weight of at least one hafnium compound in hafnium oxynitride and the remainder being silicon nitride, wherein the hard coating is made of titanium nitride, titanium carbide, titanium oxynitride,
1 of titanium oxycarbide, titanium nitrocarbide, titanium oxycarbide
An inner layer having an average layer thickness of 0.1 to 3.0 μm consisting of a single layer or a multilayer, and an outer layer having an average layer thickness of 0.1 to 3.0 μm comprising a single layer or a multilayer of aluminum oxide or aluminum oxynitride. A coated silicon nitride sintered body for a tool, comprising: 2. The method according to claim 1, wherein a surface of the outer layer is coated with a single layer or a multilayer outer layer of one kind selected from titanium nitride, titanium oxynitride, titanium nitrocarbide and titanium nitrocarbonate. Item 2. A coated silicon nitride sintered body for a tool according to Item 1.