JP5332033B2 - Sintered body - Google Patents
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- JP5332033B2 JP5332033B2 JP2008221777A JP2008221777A JP5332033B2 JP 5332033 B2 JP5332033 B2 JP 5332033B2 JP 2008221777 A JP2008221777 A JP 2008221777A JP 2008221777 A JP2008221777 A JP 2008221777A JP 5332033 B2 JP5332033 B2 JP 5332033B2
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- 239000000203 mixture Substances 0.000 claims abstract description 6
- 238000005452 bending Methods 0.000 claims description 7
- 239000000463 material Substances 0.000 description 12
- 239000002245 particle Substances 0.000 description 12
- 239000002131 composite material Substances 0.000 description 11
- 238000000034 method Methods 0.000 description 10
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 6
- 239000011218 binary composite Substances 0.000 description 3
- 239000000919 ceramic Substances 0.000 description 3
- 239000011195 cermet Substances 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 239000006185 dispersion Substances 0.000 description 3
- 239000010936 titanium Substances 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000004570 mortar (masonry) Substances 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 238000002490 spark plasma sintering Methods 0.000 description 2
- 150000003609 titanium compounds Chemical class 0.000 description 2
- UONOETXJSWQNOL-UHFFFAOYSA-N tungsten carbide Chemical compound [W+]#[C-] UONOETXJSWQNOL-UHFFFAOYSA-N 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- -1 Ti (C x Chemical class 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 229910009043 WC-Co Inorganic materials 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 229910003460 diamond Inorganic materials 0.000 description 1
- 239000010432 diamond Substances 0.000 description 1
- 239000002270 dispersing agent Substances 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 229910021480 group 4 element Inorganic materials 0.000 description 1
- 229910021478 group 5 element Inorganic materials 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
Landscapes
- Cutting Tools, Boring Holders, And Turrets (AREA)
- Ceramic Products (AREA)
Abstract
Description
本発明はＷＣを基とする焼結体に関する。より詳細には、本発明は、６０体積％以上９９体積％以下のＷＣと、１体積％以上４０体積％以下のＡｌＮ−Ｙ2Ｏ3混合物とを含み、高い熱伝導率および高い抗折力を有する焼結体に関する。 The present invention relates to a sintered body based on WC. More specifically, the present invention includes 60% by volume or more and 99% by volume or less of WC and 1% by volume or more and 40% by volume or less of an AlN—Y 2 O 3 mixture, and has high thermal conductivity and high bending strength. The present invention relates to a sintered body having
切削工具として実用されている焼結体は高硬度、高強度などを要求され、特に高負荷かつ高温という過酷な条件で実用される場合には、刃先温度上昇も工具摩耗が進行する一因である。刃先部での温度を低減させるためには、油剤またはエアブローを用いるなど強制的な冷却手段が一般的である。最近になって、工具の熱伝導率を高めて切削温度を低減させる取り組みがなされてきている。このような要求から開発された切削工具として、熱伝導率の高い窒化アルミニウムＡｌＮの特性を利用したセラミックス焼結体切削工具およびサーメット工具が提案されている（特許文献１および２参照）。 Sintered bodies that are practically used as cutting tools are required to have high hardness, high strength, etc. Especially when they are used under severe conditions such as high load and high temperature, the rise in blade temperature is also a factor that causes tool wear to progress. is there. In order to reduce the temperature at the blade edge portion, forcible cooling means such as using an oil or air blow is generally used. Recently, efforts have been made to reduce the cutting temperature by increasing the thermal conductivity of the tool. As a cutting tool developed from such a demand, a ceramic sintered body cutting tool and a cermet tool using the characteristics of aluminum nitride AlN having high thermal conductivity have been proposed (see Patent Documents 1 and 2).
前述のセラミックス焼結体切削工具は、窒化アルミニウムを１〜２５体積％と、Ｔｉ（Ｃx，Ｎy，Ｏz）で表される少なくとも１種のチタン化合物を７５〜９９体積％とを含有する焼結体である（特許文献１参照）。また、前述の窒化アルミニウム基サーメット工具は、鉄系元素とアルミニウムとを主成分とする金属相５〜３０体積％と、周期律表第４族および第５族元素の窒化物の少なくとも１種を主成分とする第１硬質相５〜３０体積％と、残部の窒化アルミニウムを主成分とする第２硬質相と、不可避不純物とを含む焼結体である（特許文献２参照）。 The aforementioned ceramic sintered body cutting tool contains 1 to 25% by volume of aluminum nitride and 75 to 99% by volume of at least one titanium compound represented by Ti (C x , N y , O z ). (See Patent Document 1). The aluminum nitride-based cermet tool described above contains 5 to 30% by volume of a metal phase mainly composed of an iron-based element and aluminum, and at least one of nitrides of Group 4 and Group 5 elements of the periodic table. It is a sintered body containing 5 to 30% by volume of the first hard phase as the main component, the second hard phase having the remaining aluminum nitride as the main component, and inevitable impurities (see Patent Document 2).
これらの焼結体は、Ｔｉ（Ｃx，Ｎy，Ｏz）またはＴｉＮのようなチタン系化合物を多量に含有することから、熱伝導率が不充分である。実際、前述のセラミックス焼結体切削工具の構成する焼結体は３０Ｗ／ｍＫ以下の熱伝導率を有する（特許文献１参照）。また、前述の窒化アルミニウム基サーメット工具を構成する焼結体は、３０Ｗ／ｍＫ以下の熱伝導率を有するとされるＴｉＮなどを多く含み、十分な放熱性能を有するとは言い難い。 Since these sintered bodies contain a large amount of a titanium-based compound such as Ti (C x , N y , O z ) or TiN, the thermal conductivity is insufficient. Actually, the sintered body constituting the ceramic sintered body cutting tool described above has a thermal conductivity of 30 W / mK or less (see Patent Document 1). Further, the sintered body constituting the above-described aluminum nitride-based cermet tool contains a large amount of TiN, which is said to have a thermal conductivity of 30 W / mK or less, and it is difficult to say that it has sufficient heat dissipation performance.
よって、本発明が解決しようとする課題は、硬さおよび強度を兼ね備えると同時に、工具材料の中でも比較的高い熱伝導率（約９０Ｗ／ｍＫ）を有するとされる超硬Ｋ１０を上回る熱伝導率を有する焼結体を提供することである。 Therefore, the problem to be solved by the present invention is to have both the hardness and the strength, and at the same time, the thermal conductivity exceeding the carbide K10, which is said to have a relatively high thermal conductivity (about 90 W / mK) among the tool materials. It is providing the sintered compact which has.
本発明者は、切削温度低減による切削工具の長寿命化および切削速度の高速化による能率向上を検討していたところ、切削工具のような集中熱源の温度上昇を緩和するためには工具母材の熱伝導率が大きく寄与することを数値解析で検証し、各種材料の熱伝導率に関する調査を行った。その結果、現状の工具材料の中ではダイヤモンドやｃＢＮなど比較的高価な材料を除いた中では、超硬Ｋ種（ＷＣ−Ｃｏ）が熱伝導率約９０Ｗ／ｍＫと高いことに着目した。 The present inventor has been studying the improvement of the efficiency by increasing the life of the cutting tool by reducing the cutting temperature and increasing the cutting speed. It was verified by numerical analysis that the thermal conductivity of the material greatly contributed, and the thermal conductivity of various materials was investigated. As a result, we focused on the fact that carbide type K (WC-Co) has a high thermal conductivity of about 90 W / mK, except for relatively expensive materials such as diamond and cBN among the current tool materials.
そこで、チタン系化合物の含有量を極力減らして、熱伝導率の高い炭化タングステン（ＷＣ）を主成分とすることを検討した。ＷＣに対して、従来技術の焼結体に使用されている窒化アルミニウムＡｌＮの添加量を変化させた焼結体を検討した結果、その混合比に適正な比率が存在するという知見を得た。本発明は、これらの知見に基づいて完成するに至ったものである。 Therefore, the inventors studied to reduce the content of the titanium compound as much as possible and to use tungsten carbide (WC) having a high thermal conductivity as a main component. As a result of examining a sintered body in which the addition amount of aluminum nitride AlN used in the prior art sintered body is changed with respect to WC, the inventors have found that an appropriate ratio exists in the mixing ratio. The present invention has been completed based on these findings.
本発明の構成を採ることによって、切削温度（刃先部最高温度）を低下させるのに十分な高い熱伝導率を有すると同時に、切削工具に要求される高硬度、高強度などの特性を満たすことができる。 By adopting the configuration of the present invention, it has a high thermal conductivity sufficient to reduce the cutting temperature (blade edge maximum temperature), and at the same time satisfies characteristics such as high hardness and high strength required for cutting tools. Can do.
本発明の焼結体は、６０〜９９体積％のＷＣと、１〜４０体積％のＡｌＮ−Ｙ2Ｏ3混合物（以下、ＡｌＮ＋Ｙ2Ｏ3と称する）を１〜４０体積％とを含む。あるいはまた、本発明の焼結材は、ＷＣおよびＡｌＮ−Ｙ2Ｏ3混合物から構成されてもよいし、第３成分を含んでもよい。第３成分は、従来から切削工具に使用されている材料、たとえばコバルト（Ｃｏ）を含む。より具体的には、本発明の焼結体は、ＷＣ、ＡｌＮ＋Ｙ2Ｏ3およびＣｏを含んでもよい。この場合、ＷＣとＡｌＮ＋Ｙ2Ｏ3との合計が焼結体の９０体積％以上を構成し、さらに、ＷＣとＡｌＮ＋Ｙ2Ｏ3との合計を基準として、ＷＣが６０体積％以上９９体積％以下であり、ＡｌＮ＋Ｙ2Ｏ3がおよび１体積％以上４０体積％以下であることが望ましい。さらに、本発明の焼結体は、不可避の不純物を含む可能性がある。 The sintered body of the present invention contains 60 to 99% by volume of WC and 1 to 40% by volume of an AlN—Y 2 O 3 mixture (hereinafter referred to as AlN + Y 2 O 3 ) of 1 to 40% by volume. Alternatively, the sintered material of the present invention may be composed of a WC and AlN—Y 2 O 3 mixture or may include a third component. The third component includes a material conventionally used for a cutting tool, for example, cobalt (Co). More specifically, the sintered body of the present invention may include WC, AlN + Y 2 O 3 and Co. In this case, the sum of WC and AlN + Y 2 O 3 constitutes 90% by volume or more of the sintered body, and WC is 60% by volume or more and 99% by volume or less based on the sum of WC and AlN + Y 2 O 3. It is desirable that AlN + Y 2 O 3 is 1 volume% or more and 40 volume% or less. Furthermore, the sintered body of the present invention may contain inevitable impurities.
上記の組成から成る本発明の焼結体は、１００Ｗ／ｍＫ以上の熱伝導率を有する。さらに、本発明の焼結体は、８００Ｎ／ｍｍ2以上の抗折力を有することが望ましい。 The sintered body of the present invention having the above composition has a thermal conductivity of 100 W / mK or more. Furthermore, the sintered body of the present invention desirably has a bending strength of 800 N / mm 2 or more.
さらに、本発明の焼結体では、その大半を占めるＷＣが連続相を形成すること、すなわち、任意の組織写真の視野内において、ＷＣが端から端まで連結された構造を有する。 Furthermore, the sintered body of the present invention has a structure in which WC occupying the majority forms a continuous phase, that is, the WC is connected from end to end within the field of view of an arbitrary structure photograph.
（１．数値解析による検証）
最初に、チップ部とホルダからなる切削工具を模擬したモデルを作成した。チップ部を縦１２．９ｍｍ×横１２．９ｍｍ×高さ４．７６ｍｍの略直方体（各面が１０度傾斜した長方形から成る）とし、ホルダを縦１５０ｍｍ×横１６ｍｍ×高さ１６ｍｍの略直方体であって、その１つの頂点に前述のチップ部の３面を保持する切り欠き（チップ保持部）を設けた形状とした。チップ先端の頂点に、縦０．６ｍｍ×横０．４ｍｍの大きさの集中熱源（出力２６Ｗ）を付加した。そして、工作機械に接触することを考慮して、チップ保持部の反対側の端面から１００ｍｍの領域のホルダの温度を３０℃に固定した。最初に、ホルダのその他の部分に１０Ｗ／ｍ2Ｋの熱伝達率を与えた場合と、断熱条件（熱伝達率０Ｗ／ｍ2Ｋ）とを比較した。その結果、両条件間の差異が０．７％程度であったため、以後の解析は断熱条件にて実施した。
(1. Verification by numerical analysis)
First, a model simulating a cutting tool consisting of a tip part and a holder was created. The tip part is a substantially rectangular parallelepiped (vertical 12.9 mm × horizontal 12.9 mm × height 4.76 mm) (each surface is made of a rectangle inclined at 10 degrees), and the holder is a substantially rectangular parallelepiped having a length 150 mm × width 16 mm × height 16 mm. Therefore, a cutout (chip holding part) for holding the three surfaces of the chip part described above was provided at one vertex. A concentrated heat source (output 26 W) having a size of 0.6 mm in length × 0.4 mm in width was added to the apex of the tip of the chip. Then, in consideration of contact with the machine tool, the temperature of the holder in the region of 100 mm from the end surface on the opposite side of the chip holding portion was fixed at 30 ° C. First, the case where a heat transfer coefficient of 10 W / m 2 K was given to the other part of the holder was compared with the heat insulation condition (heat transfer coefficient 0 W / m 2 K). As a result, since the difference between the two conditions was about 0.7%, the subsequent analysis was performed under the adiabatic conditions.
次に、チップ部に、超硬Ｋ１０相当の９６Ｗ／ｍＫの熱伝導率を設定した場合、刃先部（集中熱源を取り付けたチップ部の頂点）の最高温度は７９１℃となった。さらに、チップ部の熱伝導率を８０〜２００Ｗ／ｍＫの範囲で変化させて解析を行ったところ、図１に示す、チップ部熱伝導率と刃先部最高温度との関係が得られた。チップ部の熱伝導率が大きくなるにしたがって、刃先部最高温度も低下する傾向が認められた。たとえば、超硬Ｋ１０に対して３０％ほど熱伝導率を向上させると、約１９０℃ほど刃先部最高温度が低下する。以上の結果から、現状の超硬Ｋ１０相当の熱伝導率を少しでも向上させることが、切削温度（刃先部最高温度）を低下させる上で大きな効果を有することが分かった。 Next, when a thermal conductivity of 96 W / mK equivalent to carbide K10 was set in the tip portion, the maximum temperature of the blade edge portion (the apex of the tip portion to which the concentrated heat source was attached) was 791 ° C. Furthermore, when the analysis was performed by changing the thermal conductivity of the tip portion in the range of 80 to 200 W / mK, the relationship between the tip portion thermal conductivity and the cutting edge portion maximum temperature shown in FIG. 1 was obtained. As the thermal conductivity of the tip portion increased, the cutting edge portion maximum temperature tended to decrease. For example, when the thermal conductivity is improved by about 30% with respect to the carbide K10, the cutting edge maximum temperature decreases by about 190 ° C. From the above results, it was found that improving the thermal conductivity equivalent to the current carbide K10 has a great effect on lowering the cutting temperature (the cutting edge maximum temperature).
（２．チップ材料の熱伝導率向上について）
単一の材料の場合、その熱伝導率は物性値として固有である。したがって、熱伝導率を増大させると同時に、工具としての特性（硬さ、強度など）も満足させたい場合、２種以上の材料を複合化する方法がある。
(2. Improvement of thermal conductivity of chip material)
In the case of a single material, its thermal conductivity is unique as a physical property value. Therefore, there is a method of combining two or more kinds of materials when it is desired to satisfy the characteristics (hardness, strength, etc.) as a tool while increasing the thermal conductivity.
切削工具（特にチップ部）のように、狭い領域に集中する熱源から発生する熱を三次元的に拡散させたい場合、その材料は等方的な熱伝導率を有することが望ましい。三次元的に等方的な熱伝導率を実現するためには、多量成分が連続相となり、少量成分が連続層中に分散する複数の粒子（分散相）から成る粒子分散型の構造が望ましい。 When it is desired to three-dimensionally diffuse the heat generated from a heat source concentrated in a narrow area, such as a cutting tool (particularly, a tip portion), it is desirable that the material has isotropic thermal conductivity. In order to achieve three-dimensional isotropic thermal conductivity, a particle-dispersed structure consisting of a plurality of particles (dispersed phase) in which a large amount of component becomes a continuous phase and a small amount of component is dispersed in the continuous layer is desirable. .
最初に、連続相および分散相の熱伝導率が複合材料の熱伝導率に与える影響を解析した。連続相としてＷＣ、分散相をＡｌＮ＋Ｙ2Ｏ3とし、連続相が７０体積％を占める二成分系複合材料の熱伝導率を、粒子分散複合材料の有効熱伝導率に適用されるＭａｘｗｅｌｌの式を用いて解析した。ここで、ＷＣおよびＡｌＮ＋Ｙ2Ｏ3の単独の熱伝導率についての予備実験を行い、それらの熱伝導率が、それぞれ１１６Ｗ／ｍＫ（ＷＣ）および１５７Ｗ／ｍＫ（ＡｌＮ＋Ｙ2Ｏ3）であることを求めた。そして、連続相または分散相の一方の熱伝導率を予備実験で得られた値に固定し、他方の熱伝導率を変化させて複合材料の熱伝導率を解析した。その結果を図２に示す。図２において、７０ＷＣはＡｌＮ＋Ｙ2Ｏ3の熱伝導率を固定してＷＣの熱伝導率を変化させた場合を示し、３０ＡｌＮはＷＣの熱伝導率を固定してＡｌＮ＋Ｙ2Ｏ3の熱伝導率を変化させた場合を示す。 First, the influence of the thermal conductivity of the continuous and dispersed phases on the thermal conductivity of the composite was analyzed. The continuous phase is WC, the dispersed phase is AlN + Y 2 O 3 , the thermal conductivity of the binary composite material in which the continuous phase occupies 70% by volume, and the Maxwell formula applied to the effective thermal conductivity of the particle-dispersed composite material. And analyzed. Here, a preliminary experiment was conducted on the thermal conductivity of WC and AlN + Y 2 O 3 alone, and the thermal conductivity was 116 W / mK (WC) and 157 W / mK (AlN + Y 2 O 3 ), respectively. Asked. Then, the thermal conductivity of one of the continuous phase and the dispersed phase was fixed to the value obtained in the preliminary experiment, and the thermal conductivity of the composite material was analyzed by changing the thermal conductivity of the other. The result is shown in FIG. In FIG. 2, 70WC is to secure the thermal conductivity of the AlN + Y 2 O 3 illustrates the case of changing the thermal conductivity of the WC, 30AlN the thermal conductivity of the AlN + Y 2 O 3 by fixing the thermal conductivity of the WC The case where is changed is shown.
図２の結果から、この材料においては、分散相の熱伝導率を変化させた場合よりも、連続相の熱伝導率を変化させた場合の傾きが大きく、連続相の熱伝導率が複合材料の熱伝導率に大きく寄与することが分かった。 From the result of FIG. 2, in this material, the slope when the thermal conductivity of the continuous phase is changed is larger than that when the thermal conductivity of the dispersed phase is changed, and the thermal conductivity of the continuous phase is a composite material. It was found that it contributes greatly to the thermal conductivity of.
同様の解析を、連続相が５０体積％を占めるＷＣ−（ＡｌＮ＋Ｙ2Ｏ3）二成分系複合材料について行った。その結果を図３に示す。図３において、５０ＷＣはＡｌＮ＋Ｙ2Ｏ3の熱伝導率を固定してＷＣの熱伝導率を変化させた場合を示し、５０ＡｌＮはＷＣの熱伝導率を固定してＡｌＮ＋Ｙ2Ｏ3の熱伝導率を変化させた場合を示す。図３から明らかなように、この場合には、連続相および分散相の熱伝導率の変化の複合材料の熱伝導率に対する寄与はほぼ同等であることが分かった。 A similar analysis was performed on a WC- (AlN + Y 2 O 3 ) binary composite material in which the continuous phase occupies 50% by volume. The result is shown in FIG. In FIG. 3, 50WC is to secure the thermal conductivity of the AlN + Y 2 O 3 illustrates the case of changing the thermal conductivity of the WC, 50AlN the thermal conductivity of the AlN + Y 2 O 3 by fixing the thermal conductivity of the WC The case where is changed is shown. As is apparent from FIG. 3, in this case, it was found that the contribution of the change in the thermal conductivity of the continuous phase and the dispersed phase to the thermal conductivity of the composite material is almost the same.
以上の結果から、連続相の含有量がある一定量以上の場合、連続相の熱伝導率を増大させることが、等方的熱伝導性を有する複合材料全体の熱伝導率を増大させる点において極めて重要であることが分かった。 From the above results, when the content of the continuous phase is a certain amount or more, increasing the thermal conductivity of the continuous phase increases the overall thermal conductivity of the composite material having isotropic thermal conductivity. It turned out to be extremely important.
（実施例１）
７０体積％のＷＣ粒子（平均粒子径約１μｍ）および３０体積％のＡｌＮ＋Ｙ2Ｏ3粒子（平均粒子径約１μｍ）を秤量し、エタノールを分散剤として乳鉢中で分散させた。乾燥後、分散物をカーボンダイス中に充填し、１６００℃の温度および５０ＭＰａの圧力条件下、３０分間にわたって放電プラズマ焼結（ＳＰＳ）法によって焼結させて、焼結体を得た。なお、分散を乳鉢ではなく、たとえばボールミルなどの他の装置を用いて実施することも可能である。また、焼結法はＳＰＳ法に限定されるものではなく、後述する組織が得られることを条件として、当該技術において知られている任意の手段を用いることができる。
Example 1
70% by volume of WC particles (average particle size of about 1 μm) and 30% by volume of AlN + Y 2 O 3 particles (average particle size of about 1 μm) were weighed and dispersed in a mortar using ethanol as a dispersant. After drying, the dispersion was filled in a carbon die and sintered by a spark plasma sintering (SPS) method at a temperature of 1600 ° C. and a pressure of 50 MPa for 30 minutes to obtain a sintered body. In addition, it is also possible to carry out the dispersion using other devices such as a ball mill instead of a mortar. Further, the sintering method is not limited to the SPS method, and any means known in the art can be used on condition that a structure described later is obtained.
図４に、得られた焼結体の走査電子顕微鏡写真を示す。図４中で白く見える部分がＷＣであり、黒く見える部分がＡｌＮ＋Ｙ2Ｏ3である。図４から、得られた焼結体が、ＷＣを連続相とし、ＡｌＮ＋Ｙ2Ｏ3を分散相とする粒子分散型構造を有することが分かる。ここで、ＷＣは図面左端から右端まで連続した構造を有する。ここで、図４の画像を解析して分散相（ＡｌＮ＋Ｙ2Ｏ3）の比率を求めたところ、約３１％であった。 FIG. 4 shows a scanning electron micrograph of the obtained sintered body. In FIG. 4, the part that appears white is WC, and the part that appears black is AlN + Y 2 O 3 . FIG. 4 shows that the obtained sintered body has a particle dispersion type structure in which WC is a continuous phase and AlN + Y 2 O 3 is a dispersed phase. Here, the WC has a continuous structure from the left end to the right end of the drawing. Here, when the ratio of the dispersed phase (AlN + Y 2 O 3 ) was determined by analyzing the image of FIG. 4, it was about 31%.
図４で得られた構造に基づき、ＷＣの熱伝導率を１１６Ｗ／ｍＫとし、ＡｌＮ＋Ｙ2Ｏ3の熱伝導率を１５７Ｗ／ｍＫとして均質化法により複合材料の熱伝導率を求めたところ、１２８Ｗ／ｍＫの値が得られた。一方、実際に得られた複合材料の熱伝導率をレーザフラッシュ法で測定したところ、１３２Ｗ／ｍＫの値が得られた。このことから、本発明の数値解析が妥当であることが示された。 Based on the structure obtained in FIG. 4, the thermal conductivity of WC was 116 W / mK and the thermal conductivity of AlN + Y 2 O 3 was 157 W / mK. A value of / mK was obtained. On the other hand, when the thermal conductivity of the actually obtained composite material was measured by the laser flash method, a value of 132 W / mK was obtained. From this, it was shown that the numerical analysis of the present invention is appropriate.
（比較例１）
ＡｌＮ＋Ｙ2Ｏ3粒子に代えてＡｌＮ粒子（平均粒子径約１μｍ）を用いたことを除いて、実施例１と同様の手順により焼結体を作製した。得られた焼結体の熱伝導率をレーザフラッシュ法で測定したところ、９９Ｗ／ｍＫの値が得られた。この熱伝導率の値は、ＷＣ単独の熱伝導率よりも小さい値である。
(Comparative Example 1)
A sintered body was produced in the same procedure as in Example 1 except that AlN particles (average particle diameter of about 1 μm) were used instead of AlN + Y 2 O 3 particles. When the thermal conductivity of the obtained sintered body was measured by a laser flash method, a value of 99 W / mK was obtained. This thermal conductivity value is smaller than the thermal conductivity of WC alone.
（比較例２）
９８．５体積％のＷＣ粒子および１．５体積％のＹ2Ｏ3粒子（平均粒子径約１μｍ）を用いて、実施例１と同様の手順によって焼結体を作製した。得られた焼結体の熱伝導率をレーザフラッシュ法で測定したところ、１０５Ｗ／ｍＫの値が得られた。この結果から、分散相として存在するＹ2Ｏ3が連続相であるＷＣの熱伝導率を増大させるものではないことが明らかとなった。
(Comparative Example 2)
A sintered body was produced by the same procedure as in Example 1 using 98.5% by volume of WC particles and 1.5% by volume of Y 2 O 3 particles (average particle diameter of about 1 μm). When the thermal conductivity of the obtained sintered body was measured by a laser flash method, a value of 105 W / mK was obtained. From this result, it became clear that Y 2 O 3 existing as a dispersed phase does not increase the thermal conductivity of WC as a continuous phase.
以上の結果から、実施例１の複合材料の高い熱伝導率は、ＡｌＮまたはＹ2Ｏ3いずれか一方の効果によって得られたものではなく、ＡｌＮおよびＹ2Ｏ3が共存することによって得られたことが分かる。すなわち、連続相としてのＷＣ、分散相としてのＡｌＮ、およびＡｌＮの熱伝導率を高めるためのＹ2Ｏ3が不可欠であることが分かる。 From the above results, the high thermal conductivity of the composite material of Example 1 was not obtained by the effect of either AlN or Y 2 O 3 but was obtained by the coexistence of AlN and Y 2 O 3. I understand that. That is, it can be seen that WC as a continuous phase, AlN as a dispersed phase, and Y 2 O 3 for increasing the thermal conductivity of AlN are indispensable.
（実施例２）
連続相となるＷＣの含有量を５０〜１００体積％の範囲で変化させ、対応してＡｌＮ＋Ｙ2Ｏ3の含有量を５０〜０体積％の範囲で変化させて、実施例１と同様の手順に従って焼結体を得た。得られた焼結体の抗折力を測定した。その結果を図５に示す。図５から、ＡｌＮ＋Ｙ2Ｏ3の含有量が４０体積％を超える場合に、焼結体の抗折力が、Ａｌ2Ｏ3＋ＴｉＣの抗折力７８０Ｎ／ｍｍ2（カタログ値）を下回ることが分かった。
(Example 2)
The same procedure as in Example 1, except that the content of WC to be a continuous phase is changed in the range of 50 to 100% by volume, and the content of AlN + Y 2 O 3 is changed in the range of 50 to 0% by volume. According to the above, a sintered body was obtained. The bending strength of the obtained sintered body was measured. The result is shown in FIG. From FIG. 5, when the content of AlN + Y 2 O 3 exceeds 40% by volume, the bending strength of the sintered body is lower than the bending strength 780 N / mm 2 (catalog value) of Al 2 O 3 + TiC. I understood.
以上の結果から、熱伝導率の高いＡｌＮ＋Ｙ2Ｏ3の含有量を多くすることによって複合材料の熱伝導率は増大するが、同時に抗折力が低下することが分かった。したがって、連続相となるＷＣの含有量が６０体積％以上であり、ＡｌＮ＋Ｙ2Ｏ3の含有量が４０体積％以下であることが、熱伝導率を増大させると同時に、切削工具に要求される高硬度、高強度などの特性を満たす上で重要であることが分かった。 From the above results, it was found that increasing the content of AlN + Y 2 O 3 having high thermal conductivity increases the thermal conductivity of the composite material, but at the same time decreases the bending strength. Therefore, the content of WC serving as a continuous phase is 60% by volume or more, and the content of AlN + Y 2 O 3 is 40% by volume or less, which is required for a cutting tool as well as increasing the thermal conductivity. It was found to be important in satisfying properties such as high hardness and high strength.
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