JPH0455144B2 - - Google Patents
Info
- Publication number
- JPH0455144B2 JPH0455144B2 JP62046499A JP4649987A JPH0455144B2 JP H0455144 B2 JPH0455144 B2 JP H0455144B2 JP 62046499 A JP62046499 A JP 62046499A JP 4649987 A JP4649987 A JP 4649987A JP H0455144 B2 JPH0455144 B2 JP H0455144B2
- Authority
- JP
- Japan
- Prior art keywords
- sintered body
- cbn
- hbn
- water
- alkaline earth
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 65
- 229910052784 alkaline earth metal Inorganic materials 0.000 claims description 31
- 150000001342 alkaline earth metals Chemical class 0.000 claims description 31
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 claims description 24
- 238000000034 method Methods 0.000 claims description 22
- 229910052582 BN Inorganic materials 0.000 claims description 20
- 238000004519 manufacturing process Methods 0.000 claims description 20
- 238000011282 treatment Methods 0.000 claims description 20
- 239000003054 catalyst Substances 0.000 description 25
- 239000002245 particle Substances 0.000 description 21
- 239000011777 magnesium Substances 0.000 description 19
- 239000002994 raw material Substances 0.000 description 12
- 238000005245 sintering Methods 0.000 description 12
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 9
- 239000000463 material Substances 0.000 description 8
- 239000000843 powder Substances 0.000 description 8
- 230000015572 biosynthetic process Effects 0.000 description 6
- 239000007858 starting material Substances 0.000 description 6
- 238000004458 analytical method Methods 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 5
- 229910001873 dinitrogen Inorganic materials 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 239000011230 binding agent Substances 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 229910003460 diamond Inorganic materials 0.000 description 4
- 239000010432 diamond Substances 0.000 description 4
- 229910002804 graphite Inorganic materials 0.000 description 4
- 239000010439 graphite Substances 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 229910052749 magnesium Inorganic materials 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 238000011276 addition treatment Methods 0.000 description 3
- 239000000470 constituent Substances 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 2
- 230000002159 abnormal effect Effects 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 229910052788 barium Inorganic materials 0.000 description 2
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 2
- 244000309464 bull Species 0.000 description 2
- 238000009694 cold isostatic pressing Methods 0.000 description 2
- -1 magnesium nitride Chemical class 0.000 description 2
- 150000004767 nitrides Chemical class 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- 229910052712 strontium Inorganic materials 0.000 description 2
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 description 1
- 229910001018 Cast iron Inorganic materials 0.000 description 1
- 229910000531 Co alloy Inorganic materials 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910000997 High-speed steel Inorganic materials 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 229910000990 Ni alloy Inorganic materials 0.000 description 1
- 229910000629 Rh alloy Inorganic materials 0.000 description 1
- LIXXICXIKUPJBX-UHFFFAOYSA-N [Pt].[Rh].[Pt] Chemical compound [Pt].[Rh].[Pt] LIXXICXIKUPJBX-UHFFFAOYSA-N 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 229910001860 alkaline earth metal hydroxide Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 1
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 1
- 239000004327 boric acid Substances 0.000 description 1
- 150000001642 boronic acid derivatives Chemical class 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000004453 electron probe microanalysis Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 229910052716 thallium Inorganic materials 0.000 description 1
- BKVIYDNLLOSFOA-UHFFFAOYSA-N thallium Chemical compound [Tl] BKVIYDNLLOSFOA-UHFFFAOYSA-N 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 229910052984 zinc sulfide Inorganic materials 0.000 description 1
Description
〔産業上の利用分野〕
この発明は、たとえば工具やヒートシンク材と
して用いられる立方晶窒化硼素焼結体の製造方法
に関し、特に六方晶窒化硼素（以下、hBN）を
原料として立方晶窒化硼素焼結体（以下、cBN
焼結体）を製造する方法に関する。
〔従来の技術および発明が解決しようとする問題
点〕
cBNは、ダイヤモンドに匹敵する硬度を有す
る。また、ダイヤモンドは、700〜800℃以上の温
度に昇温されると酸化し、また鉄族元素と反応し
て消耗するのに対して、cBNは1100〜1300℃の
高温下でも酸化を起こさず、hBNへの変換もほ
とんどなく、かつ鉄族元素とも反応しない。この
ようにcBNは化学的にかつ熱的に極めて安定な
ものである。よつて、ダイヤモンドでは研削する
ことができない高速度鋼、ニツケルもしくはコバ
ルトを基質とする合金または鋳鉄などを研削する
材料として適している。さらに、cBNは、ダイ
ヤモンドに次ぐ高い熱伝導率を有し、銅よりはる
かに熱伝導率が高いので、ヒートシンク材として
も好適な材料である。
上述のような用途に使用するには、添加物の存
在しないものであるか、あるいは極めて添加物の
少ない高純度かつ高密度のcBN焼結体であるこ
とが好ましい。
しかしながら、cBN粉末を直接焼結させるこ
とは極めて難しいため、一般的には、金属、炭化
物、酸化物または窒化物などをバインダとして添
加する必要があり、その結果焼結体組織が不均一
となり、機械的強度および熱安定性が著しく低下
し、さらに熱伝導度も著しく低下しがちであつ
た。
上述の問題点を解決すべく、以下のような種々
のcBN焼結方法が知られている。
アメリカ合衆国特許第3212852号および特開昭
41−13731号には、触媒あるいはバインダを加え
ないで、hBNを原料としてcBNに直接変換する
ことにより緻密なcBN焼結体を得る方法が開示
されている。もつとも、この方法では、100Kbr
および200℃以上の高温高圧条件を必要とし、ま
た得られる製品の形状もかなり限られたものとな
る。同様に、特公昭61−2625号にも、hBNから
cBNに直接変換する方法が開示されているが、
1600℃以上の高温操作を必要とするので、やはり
生産しにくいという問題がある。
他方、アメリカ合衆国特許第4188194号、第
2947617号ならびに特開昭54−33510号には、熱分
解型窒化硼素（pBN）を原料としてcBNに直接
変換することによりcBN焼結体を得る方法が開
示されている。pBNは、その構造に未だ未知の
部分が多く、またBCl3とNH3ガスとの熱分解に
よる化学蒸着法により製造されるものであるた
め、コストも高くなるという問題がある。さら
に、特公昭54−33510号に記載されているように、
1800℃以上の高温処理を必要とするため製造上問
題がある。
その他、特開昭51−128700号には、BNの高圧
相の１つであるウルツ鉱型BN（以下、wBNと略
す）を原料として、cBN焼結体に直接変換する
方法が開示されている。しかしながら、一般に
wBNは熱力学的に不安定な非平衡状態にあるの
で原料の状態を高精度に制御しなければならな
い。このような原料状態の厳格な制御は、現実に
は極めて困難であり、そのため得られたcBN焼
結体中にhBNまたはwBNが析出し、品質が一定
しないという欠点がある。
他方、比較的緩和な条件で、しかも安価に、結
合相を含まないcBN焼結体を製造する方法が、
たとえばマテリアル・リサーチ・ブレチン
（Mat.Res.Bull）：第７巻（1972年）第999頁にお
いて若槻らの論文に示されている。ここでは、低
結晶性の六方晶型窒化硼素（hBN）を出発物質
とし、直接変換法によりcBN焼結体が得られる。
しかしながら、出発物質として用いる低結晶性
hBNは、化学的不安定であり、空気中の酸素と
反応しやすく、したがつて焼結体全体にわたり均
一かつ十分に焼結したものを得ることが困難であ
る。
一方、従来より、cBNを、hBNを原料として
触媒の存在下で超高圧・高温処理することにより
得られることは周知である。この種の触媒の代表
的なものとしては、アルカリ金属、アルカリ土類
金属およびこれらの窒化物が挙げられる。また、
水を触媒として、比較的低温条件でhBNから
cBNを合成する方法が、Mat.Res.Bull第９巻、
第1443頁（1974）に記載されている。もつとも、
この水を触媒とする方法では、硼酸塩が生成し、
cBNの粒径も非常に細かく、したがつて粒子間
結合のある緻密な焼結体を得ることはできていな
い。
他方、特公昭59−38164号および特公昭59−
38165号には、hBNよりcBNに変換するための触
媒として、硼窒化マグネシウム、硼窒化ストロン
チウム、もしくは硼窒化バリウムのようなアルカ
リ土類金属硼窒化物が開示されている。さらに、
hBN焼結体中にアルカリ土類金属硼窒化物を微
量担持させたもの（特開昭59−57966号）を、
1350℃以上の温度で超高圧・高温処理してcBN
緻密焼結体を製造する方法が、特公昭59−5547号
および特開昭59−57967号に示されている。しか
しながら、この方法においても、1350℃以上の高
温操作を必要とするため、大型試料を作成する場
合、内部まで均一に焼結させるにはかなりかなり
の高温処理を必要とする。また、この高温処理の
温度制御を正確に行なわない場合には、焼結体内
部に未焼結部分が生成し、したがつてやはり緻密
な焼結体を得ることは困難であつた。
よつて、この発明の目的は、緻密かつ高純度の
cBN焼結体を比較的低温条件下で製造すること
が可能なcBN焼結体の製造方法を提供すること
にある。
〔問題点を解決するための手段〕
この発明は、窒化硼素成型体にアルカリ土類金
属硼窒化物を担持させ、このアルカリ土類金属硼
窒化物を含む窒化硼素成型体に対して、0.005〜
1.000重量％の水を吸着拡散させ、次に立方晶窒
化硼素の熱力学的に安定な条件下で高温・高圧処
理することを特徴とする立方晶窒化硼素焼結体の
製造方法である。
アルカリ土類金属硼窒化物を担持させる六方晶
窒化硼素成型体は、hBN成型体およびhBN粉末
から構成することができるが、不純物、特に
B2O3成分を可能な限り含まない高純度のもので
あることが必要である。hBN体中にアルカリ土
類金属硼窒化物を担持させる方法としては、(a)
hBN粉末とアルカリ土類金属硼窒化物粉末とを
無水の不活性ガス、特に窒素ガス雰囲気下で混合
し、その後不活性雰囲気下で加圧・成形する方
法、あるいは(b)hBN成型体（hBN粉末の型押体
または焼結体）中にアルカリ土類金属硼窒化物を
接触または非接触により窒素気流中で拡散させる
方法がある。このようにして、アルカリ土類金属
が担持されたhBN体を得ることができる。上記
(a)および(b)のいずれの方法を採用してもよいが、
hBN成型体中に窒素気流中でアルカリ土類金属
硼窒化物を接触させた状態で熱拡散させる方法
が、担持量の多い均一な触媒担持体を簡単に得る
ことができ好ましい。この場合の担持量は原料の
hBN成型体の密度および熱拡散させる場合の加
熱温度や加熱時間により制御することができる。
また、上記担持量は、アルカリ土類金属硼窒化
物をMe3B2N4（Me：アルカリ土類金属）で表わ
した場合、0.01〜5.0モル％の範囲であることが
必要である。0.01モル％未満の場合には、一部に
未変換のhBNが残存し、緻密なcBN焼結体を得
ることができない。また、5.0モル％を超える場
合には、触媒の分散が不均一となり、得られた
cBN焼結体中に残存する触媒のために空孔がで
きやすくなり、緻密なcBN焼結体を得ることが
できない。
アルカリ土類金属硼窒化物を担持させたhBN
体中に水をさらに担持させる方法としては、一定
の温度・湿度に保つた密閉容器中に一定時間静置
し、安定かつ定量的に水を吸着・拡散させればよ
い。吸着量は、その重量増加で評価することがで
きるが、アルカリ金属硼窒化物を担持させた
hBN体に対して0.005〜1.000重量％の範囲である
ことが必要である。0.005重量％未満の場合は、
水分子がhBN成型体中のアルカリ土類金属硼窒
化物へ十分に拡散せず、所期の目的を達成するこ
とができず、したがつて未変換のhBNが焼結体
中に残存して緻密な焼結体を得ることができな
い。また、1.000重量％を超えると、hBN体中に
担持させたアルカリ土類金属硼窒化物が加水分解
し、cBN生成にとつて有害なアルカリ土類金属
水酸化物および硼酸が多量に析出し、hBNより
cBNへの変換を阻害し、その結果焼結体中に未
変換部分が生成する。
焼結条件は、cBNの熱力学的に安定な条件下
で1200℃以上の温度で行なうことが必要である。
このcBN生成条件において圧力の値は、ビスマ
ス、タリウムおよびバリウムの常温下での圧力変
化によつてもたらされる相転位を圧力定点として
それぞれ2.55、3.7、5.5GPaとして作成した、プ
レス外圧−圧力曲線に基づくものである。
また、焼結温度については、白金−白金ロジウ
ム合金熱電対を用いて測定し、黒鉛製ヒータに印
加する電力との関係を求めて評価した。
この発明の方法を実施するための超高圧装置の
一例を第１図に示す。第１図では、いわゆるガー
ドル型と呼ばれている超高圧発生装置が示されて
おり、１が超高圧発生装置のシリンダを、２がピ
ストンを、３が通電用タブレツトを、４がリング
状圧力媒体を、５がシリンダ状圧力媒体を、６が
黒鉛製ヒータを示す。加熱に際しては、ピストン
２により通電用タブレツト３を経て黒鉛製ヒータ
６に交流あるいは直流電流を印加して行なう。し
かしながら、cBN生成に必要な圧力温度条件が
得られるものであれば、特に第１図に示す超高圧
発生装置に限らず、たとえばベルト型超高圧発生
装置など公知の超高圧発生装置を用いることがで
きる。
〔作用〕
アルカリ土類金属硼窒化物に一定量の水を添加
すると、アルカリ土類金属硼窒化物の触媒機能
を著しく高め、cBN粒子の異常粒成長を抑え、
また、cBN同士の焼結を促進するなど、cBN
焼結体製造において極めて有効に水が働く。すな
わち、hBN体中にアルカリ土類金属硼窒化物を
担持させた後、一定量の水を拡散添加すれば、緻
密でしかも構成粒子が強固に結合してなる高純度
のcBN焼結体を、より低温条件下で容易に得る
ことができ、かつ得られたcBNの熱伝導率など
の特性も著しく改善される。
この発明によるcBN合成領域を第２図に示す。
第２図において、Ａ線はhBN−cBN平行曲線を
示し、このＡ線の上方がcBNの安定領域、下方
がhBNの安定領域となる。また、Ｂ線は、この
発明によるcBN生成領域を示す。Ｃ線は水を添
加しなかつた場合であつて、他の条件はこの発明
と同一とした場合のcBN生成領域を示す。第２
図より、0.005〜1.000重量％の水を吸着拡散させ
ることにより、150℃低い温度領域などcBN生成
領域の拡がることがわかる。しかも、この条件下
で得られたcBN焼結体は、後述の実施例から明
らかなように、構成粒子が相互に強固に結合して
おり、cBNのほぼ理論密度に達した緻密な焼結
体であることがわかつた。したがつて、0.005〜
1.000重量％の水を添加することにより、従来例
にない低い圧力、温度条件で緻密なcBN焼結体
を製造することができる。
また、微量の水を添加することにより、緻密な
cBN焼結体を得るために必要な触媒添加量（ア
ルカリ土類金属硼窒化物のhBN成型体中に担持
させる量）の範囲が、水を全く添加しない場合に
比べ広くなる。すなわち、水を添加しない場合
は、触媒添加量は少なくとも0.1〜0.2モル％必要
であつたが、0.005〜1.000重量％の水を添加する
ことにより、最低0.01モル％の触媒量でも緻密で
均質なcBN焼結体が得られる。したがつて、触
媒添加量をたとえば0.01〜0.1モル％と極力少な
くすることにより、触媒残留量の極めて少ない高
純度のcBN焼結体を製造することが可能となる。
但し、触媒添加量が0.01モル％以下の場合、ある
いは触媒を全く添加しなかつた場合は、0.005〜
1.000重量％の水を添加してもcBNの生成は認め
られなかつた（実施例３参照）。水のみを触媒と
してhBNからcBNへの変換を行なうためには、
数パーセント〜数十パーセントの水を添加する必
要がある。なおこの場合は、前にも述べたよう
に、硼酸塩が多く生成し、またcBN粒も極めて
小さく、粒子間結合のある強固な焼結体は得られ
ない。
他方、添加した微量の水がcBN粒子の異常粒
成長を抑えなおかつcBN同士の焼結反応を促進
する働きもある。すなわち、たとえば触媒添加量
が多い場合や焼結温度が高すぎた場合において、
水を全く添加せずに焼結を行なうと、局所的に数
10μmの粗大なcBNが析出した不均質な組織の焼
結体となることが多い。その場合、硬度、靭性な
ど機械的な特性が低下するという問題がある。一
方、0.005〜1.000重量％の水を添加すると、粒子
の揃つた均質なcBN焼結体が再現性良く得られ
らる。しかも、この場合は、水を添加しない場合
に比べ、cBN粒子同士の結合が強く、焼結後や
加工中の亀裂、粒子の脱落などの不具合も少な
い。このように、0.005〜1.000重量％の水を添加
することにより、cBN焼結体の機械的特性が飛
躍的に改善され得る。
ところで、cBN焼結体をヒートシンク材とし
て用いる場合、熱伝導率が重要な特性の１つとな
る。本発明によれば、一定量の水を原料に添加す
るすることにより、熱伝導率が室温で６〜7W／
cm・℃あるいはそれ以上の従来にない高熱伝導性
のcBN焼結体を安定して製造できる。すなわち、
BN成型体中に0.1〜2.0モル％の触媒（アルカリ
土類金属硼窒化物）を担持させ、次に0.05〜0.3
重量％の水を拡散添加し、これをcBN安定領域
内1400℃以上の温度で処理することにより、室温
で6W／cm・℃以上の高熱伝導性cBN焼結体が得
られる。ここで、触媒添加量が0.1〜2.0モル％で
あるのは以下の理由による。すなわち、触媒添加
量が0.1モル％以下では、得られるcBN焼結体の
単位粒子径が小さく（1μm程度あるいはそれ以
下）、そのためフオノン平均自由行程が減少し、
したがつて熱伝導率が低くなる傾向がある。触媒
添加量が増すに従いcBN単位粒子が大きくなり、
熱伝導率は向上するが、約2.0モル％以上になる
とcBN粒界に触媒が多く残存するようになり、
この残留触媒がフオノン散乱源となつて逆に熱伝
導率が低下する。したがつて、高熱伝導性の
cBN焼結体を製造するには、触媒添加量が0.1〜
2.0モル％の範囲内にあることが必要で、1.0モル
％前後が最も適している。
また、熱伝導率が6W／cm・℃以上の高熱伝導
性cBN焼結体を製造するためには、水添加量が
0.05〜0.3重量％の範囲内であることが必要であ
り、その理由を次に述べる。第４図は、触媒をマ
グネシウム硼窒化物（Mg3B2N4）とし、hBN成
型体中への添加量を1.0モル％とし、水添加量を
変えて作製した種々のcBN焼結体の熱伝導率を
測定した結果をまとめたものである（実施例４参
照）。この図から、水添加量が0.05〜0.3重量％の
範囲内にあるものは、熱伝導率が6W／cm・℃以
上の高い値を示すことがわかる。水添加量が少な
い場合は、前述のごとき焼結反応に及ぼす水の効
果が不十分で、そのためcBN粒子間の結合が十
分でない部分が存在し、その結果熱伝導率が低下
する傾向にある。逆に水添加量が過剰であると、
cBN粒界に酸化物、主にMgOが多く析出し、こ
れがフオノン散乱源となつて熱伝導率を低下せし
めるものと考えられる。したがつて、高熱伝導性
cBN焼結体を製造する目的においては、水の添
加量を0.05〜0.3重量％の範囲内とすることが望
ましく、0.15〜0.20重量％前後が最も適してい
る。また、高熱伝導性cBN焼結体製造において
は、焼結温度を1400℃以上にする必要がある。焼
結温度が低いと、cBN粒子が小さく、熱伝導率
が低下する傾向にある。焼結温度の上昇に伴い、
cBN粒子が大きくなり熱伝導率が向上する。
〔発明の効果〕
本発明に係る立方晶窒化硼素焼結体の製造方法
によれば、上述のようにアルカリ土類金属硼窒化
物を含む窒化硼素成型体に対して、0.005〜1.000
重量％の水を吸着拡散させる工程を採用したこと
から、緻密で均質なcBN焼結体を工業生産上有
利な条件で容易にしかも再現性良く製造すること
ができるようになる。また、本発明により得られ
るcBN焼結体は、従来のcBN焼結体に比べ、機
械的特性が優れており、切削工具などの用途に用
いることができる。また、熱伝導率が室温で６〜
7W／cm・℃あるいはそれ以上となる、従来にな
い高い熱伝導性の焼結体が得られ、ヒートシンク
材などとして最適な材料を提供し得る。
〔実施例〕
実施例 １
バインダを含まない高純度のhBN焼結体（嵩
密度1.8g/cm3）を、さらに高純度窒素ガス中、
2050℃、２時間の処理により、B2O3含有量が
0.03重量％以下になるまで精製した。このhBN焼
結体を、窒化マグネシウム粉末の中に埋め込み、
高純度窒素ガス中1165℃の温度で12時間加熱し
た。加熱処理後、取出したhBN焼結体を化学分
析およびＸ線解析により調べたところ、
Mg3B2N4がhBN焼結体中に均一に分散してお
り、その生産量は1.10モル％であつた。
このようにして得られたMg3B2N4を含むhBN
焼結体を水の入つた密封容器中の水上部に配し、
25℃の温度で45分間静置することにより、hBN
焼結体に微量の水を吸着させた。試料の重量変化
に基づき吸着した水の量を測定したところ、
Mg3B2N4を含むhBN焼結体に対して0.151重量％
の水が吸着・拡散されていることがわかつた。
この試料を第３図に示すように構成した。なお
第３図において、６は黒鉛ヒータ、７はNaCl円
板、８はNaClシリンダ、９はモリブデン容器、
１０は試料を示す。そして、第３図のように構成
された試料を、第１図に示したガードル型の超高
圧高温発生装置に組み込み、圧力5.0GPa、温度
1250℃の条件下で30分間超高圧高温処理を行なつ
た。
こうして得られた試料は淡緑色かつ半透明で強
固な焼結体であり、この焼結体をＸ線解析により
分析したところcBN単一層であることがわかつ
た。また、このcBN焼結体の表面を走査型電子
顕微鏡（SEM）により観察した結果、比較的粒
径の揃つた３〜5μmのcBN粒子が〓間なく緻密
に結合していることがわかつた。
上記cBN焼結体の室温における熱伝導率およ
びヴイツカース硬度を測定したところ、それぞれ
6.1W／cm・℃、6000〜6500Kg/mm2という高い値を
示した。また、密度は3.47g/cm3であり、理論密度
とほぼ等しいことがわかつた。
比較のため、上記と同様にしてhBN焼結体中
にMg3B2N4を添加し（添加量は1.15モル％と、
上記と同程度であつた）、水を添加せず、上記と
同一条件で超高圧高温処理を行なつたところ、
cBNの生成は全く見られず、hBNのままであつ
た。
実施例 ２
実施例１と同様の条件で、hBN焼結体中に
Mg3B2N4および水を添加した。Mg3B2N4および
水の添加量はそれぞれ1.14モル％、0.157重量％
であつた。この試料を出発物質とし、実施例１と
同様にして、圧力5.5GPa、温度1500℃の条件下
で30分間超高圧高温処理した。
得られたcBN焼結体は、比較的粒径の揃つた
cBN粒子（５〜8μm）のみからなり、理論密度
に達している極めて緻密な焼結体であることが確
かめられた。このcBN焼結体の熱伝導率は
6.4W／cm・℃、ヴイツカース硬度は6500〜7500
Kg／mm2であつた。
比較のため、水を添加しなかつたこと以外すべ
て上記と同様にしてcBN焼結体を作製した。こ
の結果、緻密なcBN単相の焼結体が得られたが、
多くの亀裂も認められた。SEMにより組織を観
察したところ、cBN粒子同士は結合しているが、
粒子は１〜20μmとやや不揃いであることがわか
つた。亀裂のない部分より試料を切り出し熱伝導
率および硬度を測定した結果はそれぞれ4.5W／
cm・℃、5000〜6500Kg/mm2であり、水を添加した
上記の結果と比べ低い値を示した。
実施例 ３
実施例１と同様の方法で、hBN焼結体中に
Mg3B2N4および水を添加した。ここでは、
Mg3B2N4の添加処理時間を30分に短縮した。そ
の結果、Mg3B2N4添加量が0.06モル％と少ない
ものが得られた。添加したMg3B2N4は微量なが
らhBN焼結体中に均一に分散していることを、
EPMAにより確認した。このような微量の
Mg3B2N4を含むhBN焼結体に対し、0.05重量％
の水を添加した。水添加処理時間は12分間で行つ
た。この試料を出発物質として、実施例１と同様
にして圧力5.5GPa、温度1450℃、30分の条件で
超高圧高温処理を行なつた。
その結果、ほとんどcBNのみからなる緻密な
焼結体が得られた。平均単位粒径は１〜2μmと極
めて微細であつた。また化学分析の結果、
Mg3B2N4をMgOが全く検出されず、極めて高純
度なcBN焼結体であることがわかつた。熱伝導
率は5.2W／cm・℃と若干低いが、ヴイツカース
硬度は7000〜7500Kg/mm2と高く、また抗析力も100
〜120Kg/mm2と高い値を示し、機械的特性に極めて
優れていることがわつた。
比較のため、hBN焼結体中へのMg3B2N4添加
量0.06モル％で水添加せずに上記と同一条件で超
高圧高温処理を行つた結果、cBNの生成が全く
認められず、hBNのままであつた。また、
Mg3B2N4を添加せずにhBN焼結体中に水のみを
添加して、上記と同じ5.5GPa、1450℃、30分の
条件で超高圧高温処理を行なつたが、水添加量
0.05、0.153、0.5重量％のいずれにおいてもcBN
の生成が認められなかつた。
実施例 ４
実施例１と同様の方法で、10個のhBN焼結体
に約1.0モル％のMg3B2N4を添加した。次に、水
添加処理時間を変えて、それぞれ水添加量の違う
試料を準備した。これら10種の試料を出発原料と
し、実施例１と同様にして、圧力5.0GPa、温度
1450℃、保持時間30分の条件で超高圧高温処理し
た。
得られたcBN焼結体の室温における熱伝導率
（Ｗ／cm・℃）、ヴイツカース硬度（Kg/mm2）を測
定した。その結果を第１表および第４図に示す。
[Industrial Application Field] The present invention relates to a method for producing cubic boron nitride sintered bodies used, for example, as tools or heat sink materials, and in particular, to a method for producing cubic boron nitride sintered bodies using hexagonal boron nitride (hereinafter referred to as hBN) as a raw material. body (hereinafter referred to as cBN
sintered body). [Prior art and problems to be solved by the invention] cBN has hardness comparable to diamond. Additionally, diamond oxidizes when heated to temperatures above 700-800℃ and is consumed by reacting with iron group elements, whereas cBN does not oxidize even at high temperatures of 1100-1300℃. , there is almost no conversion to hBN, and it does not react with iron group elements. In this way, cBN is chemically and thermally extremely stable. Therefore, it is suitable as a material for grinding high-speed steel, nickel- or cobalt-based alloys, or cast iron, which cannot be ground with diamond. Furthermore, cBN has a high thermal conductivity that is second only to diamond and is much higher than copper, making it a suitable material as a heat sink material. For use in the above-mentioned applications, it is preferable that the cBN sintered body be free of additives or contain very few additives and have high purity and high density. However, since it is extremely difficult to directly sinter cBN powder, it is generally necessary to add a metal, carbide, oxide, or nitride as a binder, which results in a non-uniform sintered body structure. Mechanical strength and thermal stability were significantly reduced, and thermal conductivity also tended to be significantly reduced. In order to solve the above-mentioned problems, various cBN sintering methods such as those described below are known. U.S. Patent No. 3212852 and JP-A-Sho
No. 41-13731 discloses a method for obtaining a dense cBN sintered body by directly converting hBN as a raw material into cBN without adding a catalyst or binder. However, with this method, 100Kbr
It requires high temperature and high pressure conditions of 200°C or higher, and the shape of the product obtained is also quite limited. Similarly, in Special Publication No. 61-2625, hBN
A method of converting directly to cBN is disclosed, but
Since it requires high-temperature operation of over 1600°C, there is still the problem that it is difficult to produce. On the other hand, U.S. Pat. No. 4,188,194, no.
No. 2947617 and JP-A-54-33510 disclose a method of obtaining a cBN sintered body by directly converting pyrolytic boron nitride (pBN) into cBN as a raw material. There are still many unknown parts of pBN's structure, and since it is manufactured by chemical vapor deposition using thermal decomposition of BCl 3 and NH 3 gas, there is a problem in that it is expensive. Furthermore, as stated in Special Publication No. 54-33510,
There are manufacturing problems because it requires high-temperature treatment of over 1800°C. In addition, JP-A-51-128700 discloses a method of directly converting wurtzite BN (hereinafter abbreviated as wBN), which is one of the high-pressure phases of BN, into a cBN sintered body as a raw material. . However, generally
Since wBN is in a thermodynamically unstable non-equilibrium state, the state of the raw material must be controlled with high precision. Such strict control of the raw material state is extremely difficult in reality, and as a result, hBN or wBN precipitates in the obtained cBN sintered body, resulting in inconsistent quality. On the other hand, there is a method for manufacturing cBN sintered bodies without a binder phase under relatively mild conditions and at low cost.
For example, it is shown in the paper by Wakatsuki et al. in Material Research Bulletin (Mat.Res.Bull): Vol. 7 (1972), p. 999. Here, low-crystalline hexagonal boron nitride (hBN) is used as a starting material, and a cBN sintered body is obtained by a direct conversion method.
However, the low crystallinity used as starting material
hBN is chemically unstable and easily reacts with oxygen in the air, making it difficult to obtain uniform and sufficient sintering throughout the sintered body. On the other hand, it has been well known that cBN can be obtained by treating hBN as a raw material at ultra-high pressure and high temperature in the presence of a catalyst. Representative catalysts of this type include alkali metals, alkaline earth metals, and nitrides thereof. Also,
From hBN under relatively low temperature conditions using water as a catalyst
The method for synthesizing cBN is described in Mat.Res.Bull Volume 9.
It is described on page 1443 (1974). However,
This water-catalyzed method produces borates,
The grain size of cBN is also very fine, so it has not been possible to obtain a dense sintered body with interparticle bonds. On the other hand, Special Publication No. 59-38164 and Special Publication No. 59-
No. 38165 discloses alkaline earth metal boronitrides such as magnesium boronitride, strontium boronitride, or barium boronitride as catalysts for converting hBN to cBN. moreover,
hBN sintered body with a trace amount of alkaline earth metal boronitride supported (Japanese Patent Application Laid-Open No. 59-57966),
cBN is produced by ultra-high pressure and high temperature treatment at a temperature of 1350℃ or higher.
A method for manufacturing a dense sintered body is shown in Japanese Patent Publication No. 59-5547 and Japanese Patent Application Laid-open No. 57967-1987. However, this method also requires high-temperature operation at 1350°C or higher, so when creating a large sample, a considerably high temperature treatment is required to uniformly sinter the inside. Furthermore, if the temperature of this high-temperature treatment is not accurately controlled, unsintered portions are formed inside the sintered body, and it is therefore difficult to obtain a dense sintered body. Therefore, the purpose of this invention is to produce a dense and highly pure
The object of the present invention is to provide a method for producing a cBN sintered body, which allows the cBN sintered body to be produced under relatively low temperature conditions. [Means for Solving the Problems] The present invention allows a boron nitride molded body to support an alkaline earth metal boronitride, and the boron nitride molded body containing the alkaline earth metal boronitride has a 0.005~
This is a method for producing a cubic boron nitride sintered body, which is characterized by adsorbing and diffusing 1.000% by weight of water, and then subjecting the cubic boron nitride to a high temperature and high pressure treatment under thermodynamically stable conditions. The hexagonal boron nitride molded body supporting alkaline earth metal boronitride can be composed of hBN molded body and hBN powder, but it is free from impurities, especially
It is necessary that it be of high purity and contain as little B 2 O 3 component as possible. As a method for supporting alkaline earth metal boronitride in hBN body, (a)
hBN powder and alkaline earth metal boronitride powder are mixed in an anhydrous inert gas atmosphere, especially nitrogen gas atmosphere, and then pressurized and molded in an inert atmosphere, or (b) hBN molded body (hBN There is a method in which an alkaline earth metal boronitride is diffused into a powder (embossed or sintered body) by contact or non-contact in a nitrogen stream. In this way, an hBN body carrying an alkaline earth metal can be obtained. the above
Either method (a) or (b) may be adopted, but
A method of thermally diffusing an alkaline earth metal boronitride in a state in which the hBN molded body is brought into contact with the alkaline earth metal boronitride in a nitrogen stream is preferable because a uniform catalyst support with a large amount of support can be easily obtained. In this case, the supported amount is the amount of raw material
It can be controlled by the density of the hBN molded body and the heating temperature and heating time when performing thermal diffusion. Further, the supported amount needs to be in the range of 0.01 to 5.0 mol % when the alkaline earth metal boronitride is expressed as Me 3 B 2 N 4 (Me: alkaline earth metal). When the amount is less than 0.01 mol%, unconverted hBN remains in part, making it impossible to obtain a dense cBN sintered body. In addition, if it exceeds 5.0 mol%, the dispersion of the catalyst will become non-uniform, resulting in
Due to the catalyst remaining in the cBN sintered body, pores are likely to be formed, making it impossible to obtain a dense cBN sintered body. hBN loaded with alkaline earth metal boronitride
As a method for further carrying water in the body, the body may be left standing in a closed container kept at a constant temperature and humidity for a certain period of time to stably and quantitatively adsorb and diffuse water. The amount of adsorption can be evaluated by the increase in weight.
It is necessary that the amount is in the range of 0.005 to 1.000% by weight based on the hBN body. If it is less than 0.005% by weight,
Water molecules do not diffuse sufficiently into the alkaline earth metal boronitride in the hBN molded body, and the intended purpose cannot be achieved, so unconverted hBN remains in the sintered body. A dense sintered body cannot be obtained. In addition, if it exceeds 1.000% by weight, the alkaline earth metal boronitride supported in the hBN body will be hydrolyzed, and a large amount of alkaline earth metal hydroxide and boric acid, which are harmful to cBN production, will precipitate. From hBN
This inhibits the conversion to cBN, resulting in the formation of unconverted portions in the sintered body. Sintering conditions need to be carried out at a temperature of 1200°C or higher under thermodynamically stable conditions for cBN.
Under these cBN production conditions, the pressure values are based on the press external pressure-pressure curves created with fixed pressure points of 2.55, 3.7, and 5.5 GPa, respectively, using phase transitions caused by pressure changes in bismuth, thallium, and barium at room temperature. It is based on Furthermore, the sintering temperature was measured using a platinum-platinum-rhodium alloy thermocouple, and evaluated by determining the relationship with the electric power applied to the graphite heater. An example of an ultrahigh pressure apparatus for carrying out the method of this invention is shown in FIG. In Fig. 1, a so-called girdle-type ultra-high pressure generator is shown, where 1 is the cylinder of the ultra-high pressure generator, 2 is the piston, 3 is the energizing tablet, and 4 is the ring-shaped pressure generator. 5 indicates a cylindrical pressure medium, and 6 indicates a graphite heater. Heating is carried out by applying alternating current or direct current to the graphite heater 6 through the energizing tablet 3 using the piston 2. However, as long as the pressure and temperature conditions necessary for cBN generation are obtained, it is not limited to the ultra-high pressure generator shown in Figure 1, but any known ultra-high pressure generator such as a belt-type ultra-high pressure generator may be used. can. [Effect] Adding a certain amount of water to alkaline earth metal boronitride significantly enhances the catalytic function of alkaline earth metal boronitride, suppresses abnormal grain growth of cBN particles,
In addition, cBN
Water works extremely effectively in the production of sintered bodies. In other words, by supporting an alkaline earth metal boronitride in an hBN body and then adding a certain amount of water by diffusion, a dense and highly pure cBN sintered body in which the constituent particles are firmly bonded can be created. It can be easily obtained under lower temperature conditions, and the properties such as thermal conductivity of the obtained cBN are also significantly improved. FIG. 2 shows the cBN synthesis region according to this invention.
In FIG. 2, line A indicates a hBN-cBN parallel curve, and the area above line A is the stable region of cBN, and the area below is the stable area of hBN. Moreover, the B line shows the cBN generation region according to the present invention. Line C shows the cBN production region when no water was added and other conditions were the same as in the present invention. Second
The figure shows that by adsorbing and diffusing 0.005 to 1.000% by weight of water, the cBN production region expands to include a 150°C lower temperature region. Moreover, the cBN sintered body obtained under these conditions is a dense sintered body whose constituent particles are strongly bonded to each other, reaching almost the theoretical density of cBN, as is clear from the examples described below. It turns out that it is. Therefore, 0.005~
By adding 1.000% by weight of water, a dense cBN sintered body can be produced under unprecedentedly low pressure and temperature conditions. In addition, by adding a small amount of water, dense
The range of the amount of catalyst added (the amount of alkaline earth metal boronitride supported in the hBN molded body) required to obtain a cBN sintered body is wider than when no water is added at all. In other words, when no water is added, the amount of catalyst added must be at least 0.1 to 0.2 mol%, but by adding 0.005 to 1.000 wt% of water, even a minimum catalyst amount of 0.01 mol% can produce a dense and homogeneous product. A cBN sintered body is obtained. Therefore, by minimizing the amount of catalyst added to, for example, 0.01 to 0.1 mol %, it is possible to produce a high purity cBN sintered body with an extremely small amount of residual catalyst.
However, if the amount of catalyst added is 0.01 mol% or less, or if no catalyst is added at all, the
No cBN formation was observed even when 1.000% by weight of water was added (see Example 3). In order to convert hBN to cBN using only water as a catalyst,
It is necessary to add several percent to several tens of percent of water. In this case, as mentioned above, a large amount of borate is produced and the cBN grains are also extremely small, making it impossible to obtain a strong sintered body with interparticle bonds. On the other hand, the small amount of water added has the function of suppressing abnormal grain growth of cBN particles and promoting the sintering reaction between cBN particles. In other words, for example, when a large amount of catalyst is added or when the sintering temperature is too high,
If sintering is carried out without adding any water, several local
It often becomes a sintered body with a heterogeneous structure in which coarse cBN of 10 μm is precipitated. In that case, there is a problem that mechanical properties such as hardness and toughness deteriorate. On the other hand, when 0.005 to 1.000% by weight of water is added, a homogeneous cBN sintered body with uniform particles can be obtained with good reproducibility. Furthermore, in this case, the bonds between cBN particles are stronger than in the case where water is not added, and there are fewer problems such as cracks and falling off of particles after sintering or during processing. Thus, by adding 0.005 to 1.000% by weight of water, the mechanical properties of the cBN sintered body can be dramatically improved. By the way, when using a cBN sintered body as a heat sink material, thermal conductivity is one of the important properties. According to the present invention, by adding a certain amount of water to the raw material, the thermal conductivity can be increased from 6 to 7 W/at room temperature.
It is possible to stably produce cBN sintered bodies with unprecedented high thermal conductivity of cm・℃ or higher. That is,
0.1 to 2.0 mol% of catalyst (alkaline earth metal boronitride) is supported in the BN molded body, and then 0.05 to 0.3
By adding % by weight of water by diffusion and treating this at a temperature of 1400°C or higher within the cBN stability region, a cBN sintered body with high thermal conductivity of 6 W/cm·°C or higher at room temperature can be obtained. Here, the reason why the amount of catalyst added is 0.1 to 2.0 mol% is as follows. That is, when the amount of catalyst added is 0.1 mol% or less, the unit particle size of the cBN sintered body obtained is small (about 1 μm or less), and therefore the phonon mean free path decreases.
Therefore, the thermal conductivity tends to be low. As the amount of catalyst added increases, the cBN unit particles become larger.
Thermal conductivity improves, but when it exceeds about 2.0 mol%, a large amount of catalyst remains at the cBN grain boundaries.
This residual catalyst becomes a source of phonon scattering, and conversely the thermal conductivity decreases. Therefore, high thermal conductivity
To produce cBN sintered bodies, the amount of catalyst added is 0.1~
It needs to be within the range of 2.0 mol%, and around 1.0 mol% is most suitable. In addition, in order to produce a highly thermally conductive cBN sintered body with a thermal conductivity of 6W/cm・℃ or higher, the amount of water added must be
It is necessary that the amount is within the range of 0.05 to 0.3% by weight, and the reason for this is described below. Figure 4 shows various cBN sintered bodies prepared by using magnesium boronitride (Mg 3 B 2 N 4 ) as a catalyst, adding 1.0 mol% of water into the hBN molded body, and changing the amount of water added. This is a summary of the results of measuring thermal conductivity (see Example 4). From this figure, it can be seen that when the amount of water added is within the range of 0.05 to 0.3% by weight, the thermal conductivity shows a high value of 6 W/cm·°C or more. When the amount of water added is small, the effect of water on the sintering reaction as described above is insufficient, and as a result, there are parts where the bonds between cBN particles are insufficient, and as a result, the thermal conductivity tends to decrease. On the other hand, if the amount of water added is excessive,
It is thought that a large amount of oxides, mainly MgO, precipitate at the cBN grain boundaries, and this becomes a source of phonon scattering, reducing the thermal conductivity. Therefore, high thermal conductivity
For the purpose of producing a cBN sintered body, it is desirable that the amount of water added be within the range of 0.05 to 0.3% by weight, and the most suitable range is approximately 0.15 to 0.20% by weight. Furthermore, in the production of highly thermally conductive cBN sintered bodies, the sintering temperature needs to be 1400°C or higher. Lower sintering temperatures tend to result in smaller cBN particles and lower thermal conductivity. As the sintering temperature increases,
cBN particles become larger and thermal conductivity improves. [Effects of the Invention] According to the method for producing a cubic boron nitride sintered body according to the present invention, as described above, for a boron nitride molded body containing an alkaline earth metal boronitride,
By adopting a process that adsorbs and diffuses % by weight of water, dense and homogeneous cBN sintered bodies can be manufactured easily and with good reproducibility under conditions that are advantageous for industrial production. Furthermore, the cBN sintered body obtained by the present invention has superior mechanical properties compared to conventional cBN sintered bodies, and can be used for applications such as cutting tools. In addition, the thermal conductivity is 6 to 6 at room temperature.
A sintered body with unprecedentedly high thermal conductivity of 7W/cm・℃ or more can be obtained, making it an ideal material for heat sink materials. [Example] Example 1 A high-purity hBN sintered body (bulk density 1.8 g/cm 3 ) containing no binder was further heated in high-purity nitrogen gas.
By treatment at 2050℃ for 2 hours, the B 2 O 3 content decreased.
It was purified to 0.03% by weight or less. This hBN sintered body is embedded in magnesium nitride powder,
It was heated at a temperature of 1165° C. for 12 hours in high purity nitrogen gas. After the heat treatment, the hBN sintered body taken out was examined by chemical analysis and X-ray analysis.
Mg 3 B 2 N 4 was uniformly dispersed in the hBN sintered body, and the production amount was 1.10 mol%. hBN containing Mg 3 B 2 N 4 obtained in this way
Place the sintered body above the water in a sealed container containing water,
hBN by standing for 45 minutes at a temperature of 25 °C.
A small amount of water was adsorbed onto the sintered body. When the amount of water adsorbed was measured based on the change in the weight of the sample,
0.151% by weight for hBN sintered body containing Mg 3 B 2 N 4
It was found that water was adsorbed and diffused. This sample was constructed as shown in FIG. In Fig. 3, 6 is a graphite heater, 7 is a NaCl disk, 8 is a NaCl cylinder, 9 is a molybdenum container,
10 indicates a sample. Then, the sample configured as shown in Figure 3 was assembled into the girdle-type ultra-high pressure and high temperature generator shown in Figure 1, and the pressure was 5.0 GPa and the temperature was 5.0 GPa.
Ultra-high pressure and high temperature treatment was performed at 1250°C for 30 minutes. The sample thus obtained was a pale green, translucent, strong sintered body, and when this sintered body was analyzed by X-ray analysis, it was found to be a cBN single layer. Furthermore, as a result of observing the surface of this cBN sintered body using a scanning electron microscope (SEM), it was found that cBN particles with a relatively uniform particle size of 3 to 5 μm were closely bonded together. When we measured the thermal conductivity and Witzkars hardness of the above cBN sintered body at room temperature, we found that
It showed high values of 6.1W/cm・℃ and 6000-6500Kg/ mm2 . In addition, the density was 3.47 g/cm 3 , which was found to be almost equal to the theoretical density. For comparison, Mg 3 B 2 N 4 was added to the hBN sintered body in the same manner as above (the amount added was 1.15 mol%,
When ultra-high pressure and high temperature treatment was performed under the same conditions as above without adding water,
No formation of cBN was observed, and hBN remained. Example 2 In the hBN sintered body under the same conditions as Example 1,
Mg3B2N4 and water were added . The amounts of Mg 3 B 2 N 4 and water added are 1.14 mol% and 0.157 wt%, respectively.
It was hot. Using this sample as a starting material, it was subjected to ultra-high pressure and high temperature treatment for 30 minutes at a pressure of 5.5 GPa and a temperature of 1500° C. in the same manner as in Example 1. The obtained cBN sintered body has a relatively uniform grain size.
It was confirmed that it was an extremely dense sintered body consisting only of cBN particles (5 to 8 μm) and reaching the theoretical density. The thermal conductivity of this cBN sintered body is
6.4W/cm・℃, Witzkaas hardness is 6500-7500
It was Kg/ mm2 . For comparison, a cBN sintered body was produced in the same manner as above except that water was not added. As a result, a dense cBN single-phase sintered body was obtained.
Many cracks were also observed. When the structure was observed using SEM, the cBN particles were bonded together, but
It was found that the particles were slightly irregular, ranging from 1 to 20 μm. A sample was cut out from the part without cracks and the thermal conductivity and hardness were measured, and the result was 4.5W/each.
cm・℃, 5000 to 6500 Kg/mm 2 , which is a lower value than the above results when water was added. Example 3 In the same manner as in Example 1, in the hBN sintered body
Mg3B2N4 and water were added . here,
The Mg 3 B 2 N 4 addition treatment time was shortened to 30 minutes. As a result, a product was obtained in which the amount of Mg 3 B 2 N 4 added was as small as 0.06 mol%. It was confirmed that the added Mg 3 B 2 N 4 was uniformly dispersed in the hBN sintered body, although in a small amount.
Confirmed by EPMA. Such a small amount
0.05% by weight based on hBN sintered body containing Mg 3 B 2 N 4
of water was added. The water addition treatment time was 12 minutes. Using this sample as a starting material, ultra-high pressure and high temperature treatment was performed in the same manner as in Example 1 at a pressure of 5.5 GPa and a temperature of 1450° C. for 30 minutes. As a result, a dense sintered body consisting almost exclusively of cBN was obtained. The average unit particle size was extremely fine, 1 to 2 μm. Also, as a result of chemical analysis,
No MgO was detected in the Mg 3 B 2 N 4 and it was found to be an extremely pure cBN sintered body. Although the thermal conductivity is slightly low at 5.2W/cm・℃, the Witzkars hardness is high at 7000-7500Kg/ mm2 , and the anti-destructive strength is also 100.
It showed a high value of ~120Kg/mm 2 and was found to have extremely excellent mechanical properties. For comparison, ultra-high pressure and high temperature treatment was performed under the same conditions as above without adding water, with Mg 3 B 2 N 4 added to the hBN sintered body at an amount of 0.06 mol%, and no cBN formation was observed. , remained hBN. Also,
Only water was added to the hBN sintered body without adding Mg 3 B 2 N 4 , and ultra-high pressure and high temperature treatment was performed under the same conditions as above at 5.5 GPa, 1450 °C, and 30 minutes, but with the addition of water amount
cBN at 0.05, 0.153, and 0.5% by weight
No formation was observed. Example 4 In the same manner as in Example 1, about 1.0 mol% Mg 3 B 2 N 4 was added to 10 hBN sintered bodies. Next, samples with different amounts of water added were prepared by changing the water addition treatment time. Using these 10 types of samples as starting materials, the same procedure as in Example 1 was carried out at a pressure of 5.0 GPa and a temperature of 5.0 GPa.
Ultra-high pressure and high temperature treatment was performed at 1450°C for 30 minutes. Thermal conductivity (W/cm·° C.) and Witzkars hardness (Kg/mm 2 ) of the obtained cBN sintered body at room temperature were measured. The results are shown in Table 1 and FIG.
【表】【table】
【表】
熱伝導率に関しては、原料への水添加量が約
0.3重量％以下のものが6W／cm・℃以上の高い値
を示し、特に水添加量0.15〜0.25重量％では
7W／cm・℃という極めて高い値を示すことがわ
かる。硬度に関しては、水添加量の増加に伴い減
少していく傾向にあり、水添加量約0.3重量％以
上では5000Kg/mm2以下となる。
水添加量が0.3重量％以上となると、cBN焼結
体内に微量ながらMgOが生成されることが、Ｘ
線解析により認められた。
実施例 ５
B2O3含有量0.2重量％のhBN粉末（粒径５〜
10μm）をCIP（冷間静水圧圧縮法）により押し固
めて、成型体を作製した。このhBN成型体を、
高純度窒素ガス中、2050℃、２時間の条件で精製
処理した。これにより、嵩密度1.7g/cm3、B2O3含
有量0.03重量％以下の高純度hBN成型体が得られ
た。このhBN成型体を原料とし、実施例１と同
様にして、Mg3B2N4添加時間を210分、水添加時
間を30分とすることにより、Mg3B2N4添加量
1.15モル％、水添加量0.18重量％のものを得た。
これを出発原料として、実施例１と同一条件で超
高圧高温処理したところ、実施例１と同様の
cBN焼結体が得られた。
得られたcBN焼結体の熱伝導率は6.2W／cm・
℃、ヴイツカース硬度は6000〜6500Kg/mm2であつ
た。
実施例 ６
実施例１で用いたのと同一のhBN焼結体を窒
化ストロンチウム粉末中に埋め込み、窒素ガス中
1150℃で12時間保持した。取出したhBN焼結体
を化学分析およびＸ線解析により調べたところ、
1.05モル％のSr3B2N4がhBN焼結体中に均一に分
散していることがわかつた。これに、実施例１と
同様の方法、条件で0.11重量％の水を添加した。
こうして得られた試料を第３図に示す構成と
し、第１図に示した超高圧発生装置により、圧力
4.8GPa、温度1200℃の条件で30分間超高圧高温
処理した。
得られた試料をＸ線解析および化学分析により
分析したところ、高純度のcBN焼結体であるこ
とがわかつた。この試料の断面をSEMにより観
察した結果、構成粒子が強固に結合した緻密な焼
結体であることがわかつた。密度はcBNの理論
値と等しく3.47ｇ/cm3であつた。また、この試料
の熱伝導率は6.2W／cm・℃、ヴイツカース硬度
は5500〜6500Kg/mm2の値を示した。
実施例 ７
実施例６と同一条件で、Ca3B2N4担持hBN焼
結体を作製した。担持量は、1.10モル％であつ
た。その後、実施例６と同一条件で水を吸着・拡
散させた。水の吸着量は、重量変化により測定し
たところ、Ca3B2N4担持hBN焼結体に対して0.12
重量％であつた。これについて、50Kbar、1250
℃の条件で15分超高圧高温処理を行なつた。
得られた試料は高純度の緻密なcBN焼結体で
あつた。このcBN焼結体の密度は、理論値と等
しく3.48ｇ/cm3を示し、熱伝導率は6.0W／cm・
℃、ヴイツカー硬度は6000〜6500Kg/mm2と高い値
を示した。[Table] Regarding thermal conductivity, the amount of water added to the raw materials is approximately
0.3% by weight or less shows a high value of 6W/cm・℃ or more, especially when the amount of water added is 0.15 to 0.25% by weight.
It can be seen that it shows an extremely high value of 7W/cm・℃. Regarding hardness, it tends to decrease as the amount of water added increases, and when the amount of water added is about 0.3% by weight or more, it becomes 5000 Kg/mm 2 or less. X
This was confirmed by line analysis. Example 5 hBN powder with B2O3 content of 0.2% by weight (particle size 5~
10 μm) was compacted by CIP (cold isostatic pressing) to produce a molded body. This hBN molded body,
Purification treatment was carried out in high purity nitrogen gas at 2050°C for 2 hours. As a result, a high purity hBN molded body having a bulk density of 1.7 g/cm 3 and a B 2 O 3 content of 0.03% by weight or less was obtained. Using this hBN molded body as a raw material, the amount of Mg 3 B 2 N 4 added was determined in the same manner as in Example 1 by setting the Mg 3 B 2 N 4 addition time to 210 minutes and the water addition time to 30 minutes.
A product was obtained in which the amount of water added was 1.15 mol% and the amount of water added was 0.18% by weight.
When this was used as a starting material and subjected to ultra-high pressure and high temperature treatment under the same conditions as in Example 1, the same results as in Example 1 were obtained.
A cBN sintered body was obtained. The thermal conductivity of the obtained cBN sintered body is 6.2W/cm・
°C, and the Witzkers hardness was 6000 to 6500 Kg/ mm2 . Example 6 The same hBN sintered body used in Example 1 was embedded in strontium nitride powder and placed in nitrogen gas.
It was held at 1150°C for 12 hours. When the extracted hBN sintered body was examined by chemical analysis and X-ray analysis, it was found that
It was found that 1.05 mol% of Sr 3 B 2 N 4 was uniformly dispersed in the hBN sintered body. To this, 0.11% by weight of water was added using the same method and conditions as in Example 1. The sample obtained in this way was constructed as shown in Figure 3, and the ultra-high pressure generator shown in Figure 1 was used to generate pressure.
Ultra-high pressure and high temperature treatment was performed at 4.8 GPa and 1200°C for 30 minutes. When the obtained sample was analyzed by X-ray analysis and chemical analysis, it was found to be a highly pure cBN sintered body. When the cross section of this sample was observed using SEM, it was found that it was a dense sintered body in which the constituent particles were firmly bonded. The density was 3.47 g/cm 3 , which is equal to the theoretical value of cBN. Further, the thermal conductivity of this sample was 6.2 W/cm·°C, and the Witzkers hardness was 5500 to 6500 Kg/mm 2 . Example 7 A Ca 3 B 2 N 4 -supported hBN sintered body was produced under the same conditions as in Example 6. The supported amount was 1.10 mol%. Thereafter, water was adsorbed and diffused under the same conditions as in Example 6. The amount of water adsorbed was 0.12 for the Ca 3 B 2 N 4 supported hBN sintered body, as measured by weight change.
It was in weight%. About this, 50Kbar, 1250
Ultra-high pressure and high temperature treatment was performed at ℃ for 15 minutes. The obtained sample was a dense cBN sintered body with high purity. The density of this cBN sintered body is 3.48 g/cm 3 , which is equal to the theoretical value, and the thermal conductivity is 6.0 W/cm.
°C and Witzker hardness showed high values of 6000 to 6500 Kg/ mm2 .
第１図は、この発明を実施するのに用いられる
超高発生装置の一例としてのガードル型超高圧発
生装置を示す略図的断面図である。第２図は、
cBN焼結体の生成領域を示す図である。第３図
は、第１図の装置に用いる試料構成を説明するた
めの断面図である。第４図は、実施例４で得られ
た結果であつて、原料hBN焼結体に添加した水
の量と、得られたcBN焼結体の室温における熱
伝導率の関係を示すグラフである。
FIG. 1 is a schematic cross-sectional view showing a girdle-type ultra-high pressure generator as an example of an ultra-high pressure generator used to carry out the present invention. Figure 2 shows
FIG. 3 is a diagram showing a region where a cBN sintered body is produced. FIG. 3 is a sectional view for explaining the sample configuration used in the apparatus of FIG. 1. FIG. 4 is a graph showing the results obtained in Example 4, showing the relationship between the amount of water added to the raw material hBN sintered body and the thermal conductivity of the obtained cBN sintered body at room temperature. .
Claims (1)
を担持させ、このアルカリ土類金属硼窒化物を含
む窒化硼素成型体に対して、0.005〜1.000重量％
の水を吸着拡散させ、次に立方晶窒化硼素の熱力
学的に安定な条件下で高温・高圧処理することを
特徴とする立方晶窒化硼素焼結体の製造方法。 ２ 上記窒化硼素成型体が、六方晶窒化硼素粉末
の型押体または焼結体である特許請求の範囲第１
項記載の立方晶窒化硼素焼結体の製造方法。 ３ 上記アルカリ土類金属硼窒化物の担持量が、
アルカリ土類金属硼窒化物をMe3B2N4（Meはア
ルカリ土類金属）とした場合に0.01〜5.00モル％
の範囲である特許請求の範囲第１項または第２項
記載の立方晶窒化硼素焼結体の製造方法。 ４ 上記高温・高圧処理を1200℃以上の温度で行
なう特許請求の範囲第１項、第２項または第３項
記載の立方晶窒化硼素焼結体の製造方法。 ５ 上記アルカリ土類金属硼窒化物の担持量が、
アルカリ土類金属硼窒化物をMe3B2N4（Meはア
ルカリ土類金属）とした場合に0.1〜2.0モル％の
範囲にあり、水を吸着拡散する量が0.05〜0.3重
量％の範囲にあり、高温・高圧処理を1400℃以上
の温度で行なう特許請求の範囲第１項または第２
項記載の立方晶窒化硼素焼結体の製造方法。[Claims] 1. An alkaline earth metal boronitride is supported on a boron nitride molded body, and 0.005 to 1.000% by weight is added to the boron nitride molded body containing the alkaline earth metal boronitride.
A method for producing a cubic boron nitride sintered body, which comprises adsorbing and diffusing water, and then subjecting the cubic boron nitride to high temperature and high pressure treatment under thermodynamically stable conditions. 2. Claim 1, wherein the boron nitride molded body is a stamped body or sintered body of hexagonal boron nitride powder.
A method for producing a cubic boron nitride sintered body as described in Section 1. 3 The amount of supported alkaline earth metal boronitride is
0.01 to 5.00 mol% when alkaline earth metal boronitride is Me 3 B 2 N 4 (Me is alkaline earth metal)
A method for manufacturing a cubic boron nitride sintered body according to claim 1 or 2, which is within the scope of claim 1 or 2. 4. The method for producing a cubic boron nitride sintered body according to claim 1, 2 or 3, wherein the high temperature/high pressure treatment is carried out at a temperature of 1200° C. or higher. 5 The amount of supported alkaline earth metal boronitride is
When alkaline earth metal boronitride is Me 3 B 2 N 4 (Me is alkaline earth metal), it is in the range of 0.1 to 2.0 mol%, and the amount that adsorbs and diffuses water is in the range of 0.05 to 0.3% by weight. Claim 1 or 2 in which the high-temperature/high-pressure treatment is performed at a temperature of 1400°C or higher
A method for producing a cubic boron nitride sintered body as described in Section 1.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/033,170 US4772575A (en) | 1986-04-09 | 1987-03-31 | Method of manufacturing sintered compact of cubic boron nitride |
| DE8787104756T DE3774744D1 (en) | 1986-04-09 | 1987-03-31 | METHOD FOR PRODUCING COMPACT SINTER BODIES FROM CUBIC BORNITRIDE. |
| EP87104756A EP0240913B1 (en) | 1986-04-09 | 1987-03-31 | Method of manufacturing sintered compact of cubic boron nitride |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61-83146 | 1986-04-09 | ||
| JP8314686 | 1986-04-09 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6345175A JPS6345175A (en) | 1988-02-26 |
| JPH0455144B2 true JPH0455144B2 (en) | 1992-09-02 |
Family
ID=13794082
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP62046499A Granted JPS6345175A (en) | 1986-04-09 | 1987-02-27 | Manufacture of cubic boron nitride sintered body |
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| Country | Link |
|---|---|
| JP (1) | JPS6345175A (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2715794B2 (en) * | 1992-03-02 | 1998-02-18 | 信越化学工業株式会社 | Method for producing molded body for producing cubic boron nitride sintered body |
| JP2000042823A (en) * | 1998-05-26 | 2000-02-15 | Sumitomo Electric Ind Ltd | Milling cutter and manufacture thereof |
| KR100932572B1 (en) * | 2003-08-20 | 2009-12-17 | 쇼와 덴코 가부시키가이샤 | Cubic boron nitride, method for producing cubic boron nitride, grinding wheel with cubic boron nitride, and sintered cubic boron nitride compact |
| JP5183256B2 (en) * | 2008-03-10 | 2013-04-17 | 独立行政法人理化学研究所 | Cutting tool and cutting method using the same |
-
1987
- 1987-02-27 JP JP62046499A patent/JPS6345175A/en active Granted
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| Publication number | Publication date |
|---|---|
| JPS6345175A (en) | 1988-02-26 |
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