JP2006232622A - Composite sintered compact and cutting tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite sintered compact capable of realizing both high hardness and high toughness. <P>SOLUTION: The composite sintered compact 1 comprises a fibrous structure formed by coating the outer periphery of a long-sized core material 4 comprising Al<SB>2</SB>O<SB>3</SB>and at least one kind of a compound selected from a group of TiC, TiN and TiCN with a surface material 8 comprising an Si<SB>3</SB>N<SB>4</SB>type sintered compact containing Mg. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a composite sintered body obtained by coating the outer periphery of a long core material with a skin material.

Conventionally, ceramic materials such as aluminum oxide (Al ₂ O ₃ ), silicon nitride (Si ₃ N ₄ ), and zirconium oxide (ZrO ₂ ) have high hardness and high strength. It is used in various applications, such as cutting tools used for cutting heat-resistant alloys, etc., and research on improvements in strength and hardness is underway.

For example, Patent Document 1 describes that composite ceramics in which fine TiC is dispersed in Al ₂ O ₃ has an effect of suppressing the progress of cracks.

In addition, in the patent document 2, the applicant of the present invention uses an outer peripheral surface of a core material containing Al ₂ O ₃ as a main component and TiC as a subcomponent as a skin material containing TiC as a main component and Al ₂ O ₃ as a subcomponent. It was proposed that by using a composite structure (composite sintered body) coated, the progress of cracks can be deflected and, as a result, the toughness of the structure can be improved.
JP-A-2-229757 JP 2003-238275 A

However, the conventional composite ceramics of Al ₂ O ₃ and TiC described in Patent Document 1 have a problem of suppressing crack growth, and have a problem of poor fracture resistance when used, for example, as a cutting tool.

  In addition, the composite sintered body described in Patent Document 2 has an effect of increasing the toughness of the sintered body, but the optimum firing temperature of the core material and the skin material is achieved with a commercially available normal raw material powder and a desired composition. There will be a difference. Therefore, it is difficult to set a firing temperature at which both the core material and the skin material are densified and can exhibit good performance, and in severe use conditions, wear resistance, particularly resistance to boundary wear is not sufficient, There was a limit to extending the service life as a cutting tool.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a composite sintered body having both high hardness and high toughness and excellent in wear resistance and fracture resistance.

As a result of examining the combination of the core material and the skin material in the long composite sintered body, the inventor has selected the core material from the group of Al ₂ O ₃ and TiC, TiN, or TiCN. The skin material contains Mg and contains Si ₃ N ₄ as a main component, so that the optimum firing temperature of the core material and the skin material can be approximated. Since the core material / skin material is an excellent sintered body having high hardness and high toughness, the composite sintered body as a whole has been found to be a composite sintered body having both high hardness and high toughness.

That is, the composite sintered body of the present invention contains Mg in the outer periphery of a long core composed of Al ₂ O ₃ and at least one compound selected from the group of TiC, TiN or TiCN. And a fibrous structure coated with a skin material mainly composed of Si ₃ N ₄ .

Here, the core material contains Al ₂ O ₃ in an amount of 90 to 10% by weight and at least one compound selected from the group of TiC, TiN, or TiCN in a proportion of 10 to 90% by weight, and the skin material includes Containing Si ₃ N ₄ in a proportion of 85 to 99.9% by weight and Mg in a proportion of 0.1 to 15% by weight in terms of MgO reduces the optimum sintering temperature of the skin material and optimizes the firing temperature of the core material This is desirable in that it can approximate the optimum sintering temperature of the core material to obtain a dense sintered body as a whole. In other words, the proper firing temperature of the Si ₃ N ₄ -based ceramics is usually higher than the proper firing temperature of the Al ₂ O ₃ —Ti compound ceramics. The temperature can be approximated.

Also, Mg contained in the skin material may be added as one kind of MgO, Mg (OH) ₂ or Mg ₃ N ₂ or a combination thereof to cause a liquid phase having a low viscosity during sintering. It is desirable in that it is easy and is effective as a so-called sintering aid that can lower the sintering temperature.

  In addition, it is desirable that the firing temperature of the composite sintered body is 1500 to 1750 ° C. in that both the core material and the skin material can be densified.

According to the composite sintered body of the present invention, the core material is composed of Al ₂ O ₃ and at least one compound selected from the group of TiC, TiN, or TiCN, and contains Mg as a skin material, and Si ₃ By using N ₄ as a main component, the optimum firing temperature of the core material and the skin material can be approximated to the same extent, and both the core material and the skin material have excellent hardness and toughness. Therefore, the composite sintered body as a whole has both high hardness and high toughness, and becomes a composite sintered body excellent in wear resistance and fracture resistance.

  As a result, the throw-away tip of the present invention has high chipping resistance even in machining conditions in which a large impact is applied to the cutting edge, such as heavy interrupted cutting used for high-speed cutting or rough machining, and chipping generated on the cutting edge. And a high wear resistance, particularly the progress of boundary wear can be suppressed, resulting in a long-life throw-away tip.

  The composite sintered body of the present invention will be described based on the schematic perspective view of FIG.

  According to FIG. 1, the composite sintered body 1 has a fibrous structure in which an outer periphery of a long core material 4 is covered with a skin material 8.

According to the present invention, the core material 4 is made of aluminum oxide (Al ₂ O ₃ ) and one or more compounds selected from the group consisting of titanium carbide (TiC), titanium nitride (TiN), and titanium carbonitride (TiCN). The main feature is that the skin material 8 is composed of a magnesium (Mg) component and silicon nitride (Si ₃ N ₄ ) as a main component.

  Thereby, the sintering temperature at which the core material and the skin material of the composite sintered body 1 are densified can be approximated to the same degree, and both the core material 4 and the skin material 8 have excellent hardness and toughness. Therefore, the composite sintered body as a whole is a composite sintered body having both high hardness and high toughness.

In addition, according to the present invention, the core material 4 has an Al ₂ O ₃ content of 90 to 90 in that it exhibits excellent wear resistance by improving hardness and improves fracture resistance by increasing toughness. 10 wt% and at least one compound selected from the group of TiC, TiN or TiCN in a ratio of 10 to 90 wt% in total, and the skin material 8 contains 85 to 99.9 Si ₃ N ₄ . It is desirable to contain Mg in a proportion of 0.1% to 15% by weight in terms of MgO as MgO.

The Mg contained in the skin material is a liquid having a low viscosity during sintering that is added to the raw material as one kind or a combination of MgO, Mg (OH) ₂ or Mg ₃ N _2. It is desirable in that it is effective in reducing the sintering temperature of the skin material as a sintering aid and approximating the optimum firing temperature of the core material.

Further, in the ceramic composed of Al ₂ O ₃ of the core material 4 and at least one compound selected from the group of TiC, TiN or TiCN, an oxide of a rare earth element, a periodic table as an auxiliary component It is desirable to contain at least one selected from the group consisting of Group 4a, 5a and 6a group metal oxides, cobalt oxide, nickel oxide, yttrium oxide, magnesium oxide and silicon oxide.

On the other hand, it is desirable that the composite ceramic of Si ₃ N ₄ and Mg of the skin material 8 contains Y ₂ O ₃ , rare earth element oxide, ZrO ₂ or the like as an additional auxiliary component.

In order to suppress the progress of cracks in the composite sintered body 1, for example, the average diameter of the core material 4 is preferably 5 to 500 μm or less, particularly preferably 5 to 300 μm. Similarly, the average thickness of the skin material 8 is 500 μm or less, preferably 0.1 to 200 μm, more preferably 0.1 to 30 μm. Similarly, it is desirable that the composite sintered body 1 has a diameter of 0.01 to 5 mm. Further, in order to achieve both high hardness and high toughness, the ratio D ₂ / D ₁ between the average diameter D ₁ of the core material 4 and the average thickness D ₂ of the skin material is 0.01 to 0.5, especially 0.8. It is desirable that it is 02-0.2.

  Furthermore, although FIG. 1 shows the case where the core material 4 is one, that is, the skin material 8 is coated around a single body, the present invention is not limited to this, as shown in FIG. For example, a multifilament structure in which a plurality of four or more structural bodies 1 are converged may be used.

  Moreover, as shown in FIG. 3, the composite sintered body 1 can also be formed into a sheet shape by arranging long ones in parallel with a predetermined length. Furthermore, (a) a method in which the long composite sintered body 1 is laminated so that each layer is oriented in the same direction, and (b) the long composite sintered body 1 is orthogonal to each other (intersection). (C) 90 °), and (c) a structure in which the long composite sintered body 1 is aligned by a method of crossing and laminating each layer so as to have a predetermined angle of 45 °, for example. Can be produced. About the lamination | stacking method of each sheet | seat, what is necessary is just to use properly the above methods according to a use.

  On the other hand, the composite sintered body 1 can have a predetermined length of, for example, 0.01 to 10 mm, and can be made into a structure in which these are randomly entangled with each other, and such a structure has characteristics such as hardness and toughness. The structure has uniform characteristics without being biased only in the direction.

  Next, an example of a method for producing the composite sintered body 1 of the present invention will be described based on the schematic diagram of FIG.

First, Al ₂ O ₃ powder having an average particle size of 0.1 to ₃ μm, TiCN powder having an average particle size of 0.5 to 5 μm, and the above-described auxiliary component powder as required are added and mixed at a predetermined ratio. Add organic binder such as paraffin wax, polystyrene, polyethylene, ethylene-ethyl acrylate, ethylene-vinyl acetate, polybutyl methacrylate, polyethylene glycol, dibutyl phthalate, and knead, press molding, extrusion molding or casting A cylindrical shaped body 12 is produced for the core material by a molding method such as molding (step (a)).

On the other hand, Si ₃ N ₄ powder having an average particle size of 0.1 to ₃ μm, MgO powder having an average particle size of 0.5 to 5 μm, and the above-described auxiliary component powder are optionally added and mixed in a predetermined ratio. The above-mentioned binder or the like is added to this. At this time, regarding the addition of the Mg component, adding one of MgO, Mg (OH) ₂ or Mg ₃ N ₂ or a combination thereof to the raw material causes a liquid phase having a low viscosity during sintering. This is desirable because it is effective in reducing the sintering temperature of the skin material as a sintering aid and approximating the appropriate sintering temperature of the core material and the skin material.

  Next, the above mixed powder is kneaded to produce two half-cylindrical shaped moldings 13 for the skin material by a known molding method such as press molding, extrusion molding or cast molding. A composite molded body 11 in which the molded body 13 is disposed so as to cover the outer periphery of the core molded body 12 is produced (step (a)).

  The composite molded body 11 is then co-extruded to produce a composite fiber molded body 15 that is covered with a skin material 13 around the core material 12 and stretched to a thin diameter (step (b)). Further, in order to produce a composite fiber molded body 16 having a multifilament structure, a plurality of the coextruded long molded bodies 15 may be converged and coextruded again (step (c)).

  Further, the elongated long composite fiber molded bodies 15 and 16 may be formed into a polygon such as a column, a triangular column, a quadrangular column, or a hexagonal column as desired. Alternatively, the long composite fiber molded bodies 15 and 16 may be aligned to form a sheet, and the sheets may be laminated such that the sheets are parallel, orthogonal, or at a predetermined angle such as 45 °. . Moreover, it is also possible to shape | mold into arbitrary shapes by shaping | molding methods, such as a well-known rapid prototyping method. Furthermore, the above-mentioned aligned sheet or a composite sintered body sheet obtained by slicing the sheet in the cross-sectional direction can be bonded to or bonded to the surface of a conventional hard alloy sintered body (lumped body) such as cemented carbide. It is.

  In addition, according to the present invention, in addition to the above method, a fibrous core material molded body is prepared first, and this is dipped (immersed and pulled up) in the slurry for the skin material as described above. It is also possible to produce a composite structure molded body.

Then, after the binder is treated to remove the binder, the composite sintered body 1 of the present invention is manufactured by firing at 1500 to 1750 ° C. under pressure in a non-oxidizing atmosphere such as N ₂ gas. Can do.

The firing temperature of the composite sintered body is desirably 1,500-1,750 ° C., whereby, with the core 4 and the skin material 8 can both _{densified, Si 3 N β-Si 3} N 4 crystal growth upon sintering of ₄ Then, there is an effect that the toughness is improved by making the needle shape. If the firing temperature is 1750 ° C. or lower, the core material and the skin material react during firing, and the composite structure of the core material and the skin material does not disappear, and the hardness and toughness of the sintered body may be significantly reduced. Absent. A particularly desirable range of the firing temperature is 1525 to 1675 ° C, and further 1575 to 1650 ° C.

  The pressurizing condition in firing is preferably 20 to 40 MPa in that firing can be performed using a known hot press facility. Further, after firing, hot isostatic pressing (HIP) firing may be performed at 1500 ° C. to 1650 ° C. as desired. By this HIP firing, the core material and the skin material can be further densified, and the wear resistance as a cutting tool is improved.

  Furthermore, with respect to the obtained composite sintered body 1, carbides, nitrides, and charcoals of Group 4a, 5a, and 6a metals of the periodic table are formed on the surface of the composite sintered body by a thin film forming method such as a CVD method or a PVD method. It is also possible to form a film of nitride or the like.

Al ₂ O ₃ powder with an average particle size of 0.3 μm, TiC powder with an average particle size of 0.8 μm, TiN powder with an average particle size of 0.9 μm, Yb ₂ O ₃ powder with an average particle size of 1 μm, average particle size of 0 .5 μm Co ₃ O ₄ powder, TiO ₂ powder having an average particle size of 0.5 μm, and Mg ₃ N ₂ powder having an average particle size of 0.5 μm were prepared in the proportions shown in Table 1 (materials A, B, and C). . 50 parts by volume of ethyleneethyl acrylate, ethylene vinyl acetate, and methoxypolyethylene glycol were added as organic binders to the blended powder and kneaded, and extruded into a cylindrical shape to produce a core material.

On the other hand, Si ₃ N ₄ powder having an average particle diameter of 0.3 μm, Mg (OH) ₂ powder having an average particle diameter of 1 μm, and Y ₂ O ₃ powder having an average particle diameter of 1 μm are weighed in the proportions shown in Table 1 (materials). D, E, F), and the same organic binder as described above is added and kneaded to produce two half-cylindrical skin material moldings by extrusion, and the outer periphery of the core molding The composite molded body was produced by arranging so as to cover. Further, a SiC sintered material having a composition of Table 1 material G was prepared using SiC powder having an average particle diameter of 1 μm, Yb ₂ O ₃ powder having an average particle diameter of 1 μm, and the above raw materials.

Then, the composite molded body is coextruded to produce a stretched composite fiber molded body having a diameter of 2 mm, and then 100 stretched composite fiber molded bodies are converged and coextruded again, and the diameter is 1 mm. A multi-type composite fiber molded body was produced.

  Next, this multi-type composite fiber molded body is cut every 3 mm in length, and the cut fibers are randomly filled in a carbon mold and then molded in a state heated to 140 ° C. to form a composite fiber Got the body.

  Then, after performing binder removal processing by heating up to 100-700 degreeC with respect to the said molded object in 70 hours, it heated up at the temperature increase rate of 10 degree-C / min, and shows in Table 2 under the pressurization of 30 MPa. The composite sintered body was produced by firing with a hot press at a temperature for 1 hour. When the cross section of the composite sintered body was observed, the diameter of the core material was 20 μm, the thickness of the skin material was 1 μm, and no peeling or the like was observed between the core material and the skin material.

  Then, this composite sintered body is processed into an RNGN120700 type cutting tool shape, and further subjected to throwing away by performing C surface processing and / or R honing processing so that the core material is exposed at the cutting edge tip portion of the corner portion. A type of cutting tool was made.

  The obtained throwaway tip was subjected to a cutting test for cutting for a maximum of 15 minutes under the following conditions. In addition, about the sample which endured cutting for 15 minutes, the boundary wear width was measured and the result was shown in Table 2.

<Cutting conditions>
Work material: Inconel 718
Cutting speed 300m / min
Cutting depth: 1mm
Feed 0.2mm / rev
Condition: wet cutting

From the results of Tables 1 and 2, Sample No. in which no Mg component was added to the Si ₃ N ₄ sintered material of the skin material. 3 and 4 became chipping during the test due to chipping. Sample No. using a SiC sintered body as the skin material was used. In No. 5, wear progressed early, resulting in a cutting stop during the test, all of which had a short tool life.

On the other hand, in accordance with the present invention, sample No. 1 using an Al ₂ O ₃ —Ti compound sintered body as the core material and an Si ₃ N ₄ sintered body containing Mg as the skin material. In 1 and 2, both showed good cutting performance.

It is a schematic perspective view which shows an example of the composite sintered compact of this invention. It is a figure which shows the example combined with the multifilament form of the composite sintered compact of this invention. It is a figure which shows the example combined with the flat form of the composite sintered compact of FIG. It is a conceptual diagram for demonstrating the manufacturing method of the composite sintered compact of this invention.

Explanation of symbols

1 Composite sintered body 4 Core material 8 Skin material

Claims (5)

The outer periphery of a long core composed of Al ₂ O ₃ and at least one compound selected from the group consisting of TiC, TiN and TiCN is made of a Si ₃ N ₄ sintered material containing Mg. A composite sintered body having a fibrous structure coated with a skin material. The core material contains 90 to 10% by weight of Al ₂ O ₃ and at least one compound selected from the group of TiC, TiN or TiCN in a proportion of 10 to 90% by weight, and the skin material is Si ₃ N. The composite sintered body according to claim 1, wherein ₄ is contained at 85 to 99.9 wt% and Mg is contained at a ratio of 0.1 to 15 wt% in terms of MgO. _3. The composite sintered body according to claim 1, wherein Mg contained in the skin material is added as one kind of MgO, Mg (OH) _2, or Mg ₃ N ₂ or a combination thereof. The composite sintered body according to any one of claims 1 to 3, which is fired at 1500 to 1750 ° C under pressure in a non-oxidizing atmosphere. A cutting tool for cutting with a cutting edge applied to a work material, wherein at least the cutting edge is made of the composite sintered body according to any one of claims 1 to 4.

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