JP2004026633A - Boron carbide-chromium diboride sintered compact and its manufacturing method - Google Patents
Boron carbide-chromium diboride sintered compact and its manufacturing method Download PDFInfo
- Publication number
- JP2004026633A JP2004026633A JP2003092454A JP2003092454A JP2004026633A JP 2004026633 A JP2004026633 A JP 2004026633A JP 2003092454 A JP2003092454 A JP 2003092454A JP 2003092454 A JP2003092454 A JP 2003092454A JP 2004026633 A JP2004026633 A JP 2004026633A
- Authority
- JP
- Japan
- Prior art keywords
- boron carbide
- sintered body
- chromium
- diboride
- chromium diboride
- 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.)
- Granted
Links
Landscapes
- Ceramic Products (AREA)
Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、炭化硼素−二硼化クロム焼結体及びその製造方法等に関するものであり、更に詳しくは、非加圧条件化で焼結することによって作製した焼結体であって、高い密度を有する炭化硼素−二硼化クロム焼結体、更に、高い導電率を持ち、高い曲げ強度を有すると共に、高い破壊靭性値を兼ね備えた炭化硼素−二硼化クロム焼結体、それらの製造方法、及び耐摩耗性部材に関するものである。
【０００２】
【従来の技術】
一般に、炭化硼素焼結体は、軽量で高い硬度を有し、耐摩耗性や耐腐食性に優れた材料であり、現状では、サンドブラストノズル、線引きダイス、押し出しダイス等に使用されている。しかしながら、炭化硼素焼結体は、難焼結性であり、通常は、ホットプレス法により作製されている。この製造方法は、生産コストが高いことから炭化硼素焼結体の一般的な応用を妨げている。そこで、ホットプレス法に代わって、非加圧条件下（常圧法）で加熱（焼結）することにより、炭化硼素焼結体を作製することが検討されている。例えば、先行技術文献（非特許文献１参照）では、焼結助剤として、炭素を添加し、非加圧条件下にて炭化硼素焼結体を作製しているが、２１５０℃以上の極めて高い温度で焼結する必要があることから、実用上好ましくない。
【０００３】
【非特許文献１】
Ｋ．Ａ．Ｓｃｈｗｅｔｚ，Ｊ．Ｓｏｌｉｄ Ｓｔａｔｅ Ｃｈｅｍｉｓｔｒｙ１３３，１７７−８１（１９９７）
【０００４】
更に、炭化硼素焼結体は、その硬度が極めて高いことから、通常の研削・研磨法では加工し難く、また、炭化硼素焼結体の導電率が１０〜３００Ｓ／ｍのレベルと低いために、放電加工が困難である、という問題があった。
上記の様に、炭化硼素焼結体は、難焼結性、難加工性であることから、現状では、極めて限定された用途にのみ使用されているのが実情である。
【０００５】
【発明が解決しようとする課題】
このような状況の中で、本発明者らは、上記従来技術に鑑みて、非加圧条件下にて焼結することにより、緻密で高強度、高靭性の炭化硼素−二硼化クロム焼結体の研究／開発を鋭意進める過程で、特定の物性を有する炭化硼素粉末に二硼化クロムを所定量添加し、非加圧条件下にて二硼化クロムの液相が発生する液相焼結を行って、それにより、特定の微細組織を有し、導電性の高い二硼化クロム相が３次元的にネットワーク構造を形成した焼結体を作製することで、優れた特性を持つ炭化硼素−二硼化クロム焼結体が得られることを見出し、本発明を完成するに至った。
【０００６】
即ち、本発明は、相対密度が９０％以上であり、５×１０２ Ｓ／ｍ以上の導電率を持ち、４００ＭＰａ以上の四点曲げ強度を有すると共に、３．０ＭＰａ・ｍ１／２ 以上の破壊靱性値を兼ね備えた炭化硼素−二硼化クロム焼結体、及びそれらを非加圧条件下にて焼結することによって製造する方法、及びそれらの用途を提供することを目的とするものである。
【０００７】
【課題を解決するための手段】
上記課題を解決するための本発明は、以下の技術的手段から構成される。
（１）炭化硼素粉末に二硼化クロム粉末を所定量添加し、混合してなる原料粉末を、成形した後、非加圧条件下で二硼化クロムの液相が発生する液相焼結を行うことにより二硼化クロム相が３次元的なネットワーク構造を形成した焼結体を作製することを特徴とする炭化硼素−二硼化クロム焼結体の製造方法。
（２）平均粒径（Ｄ５０）が２μｍ以下で、比表面積が１０ｍ２ ／ｇ以上である炭化硼素粉末を用いる、前記（１）記載の方法。
（３）平均粒径（Ｄ５０）が８μｍ以下の二硼化クロム粉末を用いる、前記（１）記載の方法。
（４）炭化硼素粉末に二硼化クロム粉末を１０〜２５ｍｏｌ％添加する、前記（１）記載の方法。
（５）非酸化性雰囲気下の非加圧条件下で１９５０〜２１００℃に加熱して液相焼結を行う、前記（１）記載の方法。
（６）前記（１）から（５）のいずれかに記載の方法により得られる炭化硼素（Ｂ４ Ｃ）に二硼化クロム（ＣｒＢ２ ）を１０〜２５ｍｏｌ％含有する炭化硼素−二硼化クロム焼結体であって、当該焼結体の相対密度が９０％以上であり、前記焼結体中の炭化硼素粒子の最大粒子径が１００μｍ以下であり、粒子径５μｍ以下の炭化硼素粒子に対する１０〜１００μｍの炭化硼素粒子の存在比（面積比）が０．０２〜０．６であることを特徴とする炭化硼素−二硼化クロム焼結体。
（７）５×１０２ Ｓ／ｍ以上の導電率を有することを特徴とする前記（６）記載の炭化硼素−二硼化クロム焼結体。
（８）四点曲げ強度が４００ＭＰａ以上であり、破壊靱性値が３．０ＭＰａ・ｍ１／２ 以上であることを特徴とする前記（６）記載の炭化硼素−二硼化クロム焼結体。
（９）前記（６）から（８）のいずれかに記載の炭化硼素に二硼化クロムを１０〜２５ｍｏｌ％含有する炭化硼素−二硼化クロム焼結体を構成要素として含むことを特徴とする耐摩耗性部材。
【０００８】
【発明の実態の形態】
次に、本発明について更に詳細に説明する。
非加圧条件下で焼結することにより、緻密な炭化硼素系焼結体を作製するには、ある程度の炭化硼素の粒成長が必要であり、粒成長がまったく起こらないと、高い密度の焼結体が得られない。一方、粒成長が進みすぎると、粗大粒子が緻密化の障害となり、返って焼結体密度が低下し、また、粗大粒子が破壊起点となって曲げ強度が低下する。本発明では、特定の物性を有する炭化硼素粉末を用い、二硼化クロム（ＣｒＢ２ ）を主成分とする液相が発生する温度領域にて、特定の非加圧条件下で焼結を行うことにより、炭化硼素粒子の最大粒子径が１００μｍ以下であり、粒子径５μｍ以下の炭化硼素粒子に対する１０から１００μｍの炭化硼素粒子の存在比（面積比）が０．０２から０．６の範囲であって、相対密度が９０％以上であり、導電性の高い二硼化クロム相が３次元的にネットワーク構造を形成しており、５×１０２ Ｓ／ｍ以上の導電率を持ち、４００ＭＰａ以上の四点曲げ強度を有し、かつ３．０ＭＰａ・ｍ１／２ 以上の破壊靱性値を有することを特徴とする炭化硼素−二硼化クロム焼結体、が作製される。
【０００９】
本発明に用いる炭化硼素粉末としては、好適には、レーザー回折散乱法やドップラー法にて測定した平均粒径（Ｄ５０） ：２μｍ以下のものがあげられる。平均粒径（Ｄ５０）が２μｍより大きいと、焼結性が劣り、１９５０〜２１００℃の温度範囲で緻密な焼結体が得られず、それを緻密化するためには粒成長が起こり易い、より高い温度で焼結する必要があり、曲げ強度の劣化をまねく可能性がある。比表面積（ＢＥＴ） については、好ましくは焼結性が良好な１０ｍ２ ／ｇ以上の炭化硼素粉末を用い、より好ましくは１５ｍ２ ／ｇ以上のものを用いるのがよい。
【００１０】
前記の物性を有する炭化硼素粉末は、ふるい分け、沈降分離、粉砕等の手段によって調製し得るが、前記物性を有する市販品を入手して使用してもよい。
上記の物性を有する炭化硼素粉末に二硼化クロム粉末を１０〜２５ｍｏｌ％添加し、成形した後に、真空中或いはＡｒ等非酸化性雰囲気下の非加圧条件下で１９５０〜２１００℃の焼結温度範囲で、二硼化クロム系液相を発生させた状態にて加熱（焼結）を行う。
【００１１】
二硼化クロム粉末は、焼結中に一部の炭化硼素粉末と反応して溶融し、二硼化クロム系液相を発生し、炭化硼素粒子間に浸透することから、炭化硼素粉末に比較して、粒径の大きな原料粉末でも使用でき、好ましくは、平均粒径（Ｄ５０）が８μｍ以下の二硼化クロム粉末を用いることができ、より好ましくは平均粒径（Ｄ５０）が４μｍ以下のものを使用することができる。
【００１２】
焼結温度が１９５０℃より低い場合には、二硼化クロム系液相が発生しないことから、十分に緻密な炭化硼素焼結体が作製できず、二硼化クロム相の３次元的なネットワーク構造が形成されず、そのために、高い導電率が得られない。また、２１００℃より高い焼結温度では、粒成長により粗大な炭化硼素粒子が生成し、曲げ強度の低下を招く可能性がある。
【００１３】
二硼化クロムの添加量が１０ｍｏｌ％未満であると、十分な量の二硼化クロム系液相が生成しないことから、緻密な焼結体が得られず、導電率及び破壊靭性値の改善効果も十分でない。また、二硼化クロムの添加量が２５ｍｏｌ％より多い場合には、焼結体の密度が３． ０ｇ／ｃｍ３ よりも高くなり、炭化硼素系焼結体の軽量性の特徴が損なわれ、硬度も低下する。本発明の方法により作製された炭化硼素−二硼化クロム焼結体は、優れた特性を有し、耐摩耗性部材として有用である。本発明において、上記耐摩耗性部材とは、摺動部品、切削工具、耐摩耗性部品などのあらゆる種類の部材を包含するものであることを意味している。
【００１４】
【作用】
本発明では、非加圧条件下にて二硼化クロムの液相が発生する液相焼結を行って、特定の微細構造を有し、導電性の高い二硼化クロム相が３次元的にネットワーク構造を形成した焼結体を作製することで、優れた特性を有する炭化硼素−二硼化クロム焼結体を作製することができる。本発明の炭化硼素−二硼化クロム焼結体は、二硼化クロムの熱膨張率が炭化硼素より大きいため、破壊の進行時に炭化硼素粒子と二硼化クロム相との界面近傍にて亀裂の伝播の迂回やマイクロクロックが発生することによって、破壊靭性値が改善される。また、最大粒子サイズが１００μｍ以下であること、二硼化クロム系液相による溶解・析出機構によって、炭化硼素粒子の突起部分が消失して応力集中が緩和されること、炭化硼素粒子が二硼化クロム相によって結合されるため、加工時に炭化硼素粒子の脱落が抑制されることや破壊靭性値が改善されることにより、強度が改善され、４００ＭＰａ以上の高い曲げ強度が得られる。
【００１５】
【実施例】
以下に、本発明の内容を、実施例及び比較例により具体的に説明するが、本発明は、以下の実施例によって何ら限定されるものではない。
実施例１
表１に示す物性を有する炭化硼素粉末Ｉに、平均粒径（Ｄ５０）：３．５μｍの二硼化クロム粉末をそれぞれ２０ｍｏｌ％配合し、メタノール溶媒を用いて、ＳｉＣ製遊星ボールミルにて回転数：２７５ｒｐｍ、１時間の混合を行った。スラリーをエバポレーターで乾燥させ、更に、１５０℃、２４時間の乾燥を行った後に、２５０ｍｅｓｈのふるいに通して、炭化硼素−二硼化クロム混合粉末を調製した。２０ＭＰａにて金型成形した後、２００ＭＰａのＣＩＰ成形を行って成形体を作製した。黒鉛製容器に成形体を入れ、抵抗加熱式焼結炉に取り付けた。拡散ポンプを用いて２． ０×１０−１〜２． ０×１０−２Ｐａの圧力に真空引きをしながら、４０℃／分の昇温速度にて加熱を行った。１０００℃に到達した時に真空引きを終了してＡｒガスを導入し、１５００℃まで加熱した。１５００℃から２０３０℃までは１０℃／ｍｉｎ昇温速度にて加熱した。２０３０℃に到達した後、非加圧条件下で１時間の焼結を行って炭化硼素−二硼化クロム焼結体を作製した。
【００１６】
【表１】
炭化硼素焼結体の四点曲げ強度及び破壊靭性値を、それぞれ、ＪＩＳ Ｒ１６０１、ＪＩＳ Ｒ１６０７に基づいて測定した。テストピースの表面は、平面研削盤 ４００番にて仕上げた。また、アルキメデス法にてテストピースの密度を測定し、相対密度を計算した。テストピースの表面をラッピングし、エッチング処理を行った後に、ＳＥＭ観察を行い、画像処理を行うことによって、炭化硼素の最大粒子径、及び粒子径５μｍ以下の炭化硼素粒子に対する１０から１００μｍの炭化硼素粒子の存在比（面積比）を測定した。導電率は４端子法を用いて測定した。
【００１８】
評価の結果を表２に示す。得られた焼結体は、９０％以上の相対密度を持ち、最大粒子径が１００μｍ以下であり、炭化硼素粒子の存在比（面積比）が０．０２〜０．６の範囲内にあり、５×１０２ Ｓ／ｍ以上の導電率を有し、４００ＭＰａ以上の四点曲げ強度及び３．０ＭＰａ・ｍ１／２ 以上の破壊靱性値を有していた。
【００１９】
【表２】
実施例２
表１に示す物性を有する炭化硼素粉末ＩＩに、平均粒径（Ｄ５０）：３．５μｍの二硼化クロム粉末をそれぞれ２０ｍｏｌ％配合し、メタノール溶媒を用いて、ＳｉＣ製遊星ボールミルにて回転数：２７５ｒｐｍ、１時間の混合を行った。スラリーをエバポレーターで乾燥させ、更に、１５０℃、２４時間の乾燥を行った後に、２５０ｍｅｓｈのふるいに通して、炭化硼素−二硼化クロム混合粉末を調製した。２０ＭＰａにて金型成形した後、２００ＭＰａのＣＩＰ成形を行って成形体を作製した。黒鉛製容器に成形体を入れ、抵抗加熱式焼結炉に取り付けた。拡散ポンプを用いて２． ０×１０−１〜２． ０×１０−２Ｐａの圧力に真空引きをしながら、４０℃／分の昇温速度にて加熱を行った。１０００℃に到達した時に真空引きを終了してＡｒガスを導入し、１５００℃まで加熱した。１５００℃から２０３０℃までは１０℃／ｍｉｎ昇温速度にて加熱した。２０３０℃に到達した後、非加圧条件下で１時間の焼結を行って炭化硼素−二硼化クロム焼結体を作製した。
【００２１】
炭化硼素焼結体の四点曲げ強度及び破壊靭性値を、それぞれ、ＪＩＳ Ｒ１６０１、ＪＩＳ Ｒ１６０７に基づいて測定した。テストピースの表面は、平面研削盤 ４００番にて仕上げた。また、アルキメデス法にてテストピースの密度を測定し、相対密度を計算した。テストピースの表面をラッピングし、エッチング処理を行った後に、ＳＥＭ観察を行い、画像処理を行うことによって、炭化硼素の最大粒子径、及び粒子径５μｍ以下の炭化硼素粒子に対する１０から１００μｍの炭化硼素粒子の存在比（面積比）を測定した。導電率は４端子法を用いて測定した。
【００２２】
評価の結果を表２に示す。得られた焼結体は、９０％以上の相対密度を持ち、最大粒子径が１００μｍ以下であり、炭化硼素粒子の存在比（面積比）が０．０２〜０．６の範囲内にあり、５×１０２ Ｓ／ｍ以上の導電率を有し、４００ＭＰａ以上の四点曲げ強度及び３．０ＭＰａ・ｍ１／２ 以上の破壊靱性値を有していた。
【００２３】
比較例１
表１に示す物性を有する炭化硼素粉末ＩＩＩ を用いたこと以外は、上記実施例１〜２と同様の手順にて、非加圧条件下で焼結を行って、炭化硼素−二硼化クロム焼結体を作製し、評価を行った。
表２に、評価の結果を示す。比較例１では、平均粒径（Ｄ５０）が２μｍより大きく、比表面積（ＢＥＴ） が１０ｍ２ ／ｇより小さい炭化硼素粉末を用いたため、緻密な焼結体ができずに、炭化硼素粒子の存在比（面積比）が、０．０２〜０．６の範囲内からはずれ、曲げ強度及び破壊靭性値は低い値となった。
【００２４】
実施例３
炭化硼素粉末Ｉに、上記実施例１〜２と同じ二硼化クロム粉末を、１５ｍｏｌ％配合し、上記実施例１〜２と同様な手順にて、炭化硼素−二硼化クロム混合粉末を調製した。焼結温度２０５０℃としたこと以外は上記実施例１〜２と同様の手順にて非加圧条件下で焼結を行って、炭化硼素−二硼化クロム焼結体を作製し、評価を行った。
評価の結果を表２に示す。得られた焼結体は、９０％以上の相対密度を持ち、最大粒子径が１００μｍ以下であり、炭化硼素粒子の存在比（面積比）が０．０２〜０．６の範囲内にあり、５×１０２ Ｓ／ｍ以上の導電率を有し、４００ＭＰａ以上の四点曲げ強度及び３．０ＭＰａ・ｍ１／２ 以上の破壊靱性値を有していた。
【００２５】
実施例４
炭化硼素粉末Ｉに、上記実施例１〜２と同じ二硼化クロム粉末を、２２．５ｍｏｌ％配合し、上記実施例１〜２と同様な手順にて、炭化硼素−二硼化クロム混合粉末を調製した。焼結温度２０２０℃としたこと以外は上記実施例１〜２と同様の手順にて非加圧条件下で焼結を行って、炭化硼素−二硼化クロム焼結体を作製し、評価を行った。
評価の結果を表２に示す。得られた焼結体は、９０％以上の相対密度を持ち、最大粒子径が１００μｍ以下であり、炭化硼素粒子の存在比（面積比）が０．０２〜０．６の範囲内にあり、５×１０２ Ｓ／ｍ以上の導電率を有し、４００ＭＰａ以上の四点曲げ強度及び３．０ＭＰａ・ｍ１／２ 以上の破壊靱性値を有していた。
【００２６】
比較例２
二硼化クロム粉末の配合量を７．５ｍｏｌ％としたこと以外は、上記実施例１〜２と同様の手順にて、非加圧条件下で焼結を行って、炭化硼素−二硼化クロム焼結体を作製し、評価を行った。
評価の結果を表２に示す。二硼化クロム粉末の配合量が低く、十分な量の二硼化クロム系液相が発生しないため、緻密な焼結体が得られず、炭化硼素粒子の存在比（面積比）が、０．０２〜０．６の範囲内からはずれ、導電率は改善されず、曲げ強度及び破壊靭性値は低い値となった。
【００２７】
【発明の効果】
以上詳述したように、本発明は、炭化硼素−二硼化クロム焼結体及びその製造方法等に係るものであり、本発明により、１）導電性の高い二硼化クロム相が３次元的にネットワーク構造を形成した焼結体が得られる、２）本発明の炭化硼素−二硼化クロム焼結体は、低い焼結温度にて非加圧条件下（常圧法）で加熱（焼結）することにより作製することが可能である、３）高い焼結体密度を有し、導電性が良好であり、放電加工による加工が可能である、４）新しい耐摩耗性部材を提供することができる、更に、５）本発明の炭化硼素−二硼化クロム焼結体は、強度・靭性が高く、機械的特性が優れるので、摺動部品、切削工具や新しい耐摩耗性部品等、いろいろな用途で用いられることができ、産業上有用である、という格別の効果が奏される。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a boron carbide-chromium diboride sintered body and a method for producing the same, and more particularly, to a sintered body produced by sintering under non-pressurized conditions, and , A boron carbide-chromium diboride sintered body having a high electrical conductivity, a high bending strength, and a high fracture toughness, and a method for producing the same. , And a wear-resistant member.
[0002]
[Prior art]
Generally, a boron carbide sintered body is a material that is lightweight, has high hardness, and is excellent in wear resistance and corrosion resistance, and is currently used for a sandblast nozzle, a drawing die, an extrusion die, and the like. However, the boron carbide sintered body is difficult to be sintered, and is usually manufactured by a hot press method. This production method hinders general application of the boron carbide sintered body due to high production costs. Therefore, it has been studied to produce a boron carbide sintered body by heating (sintering) under non-pressurized conditions (normal pressure method) instead of the hot press method. For example, in the prior art document (see Non-Patent Document 1), carbon is added as a sintering aid, and a boron carbide sintered body is produced under non-pressurized conditions. Since it is necessary to sinter at a temperature, it is not practically preferable.
[0003]
[Non-patent document 1]
K. A. Schwetz, J .; Solid State Chemistry 133, 177-81 (1997)
[0004]
Furthermore, since the hardness of the boron carbide sintered body is extremely high, it is difficult to process by a normal grinding and polishing method, and the conductivity of the boron carbide sintered body is as low as 10 to 300 S / m. However, there is a problem that electric discharge machining is difficult.
As described above, the boron carbide sintered body is difficult to be sintered and difficult to process, and is currently used only for extremely limited applications at present.
[0005]
[Problems to be solved by the invention]
In such a situation, the present inventors considered in view of the above-mentioned prior art that by sintering under non-pressurized conditions, a dense, high-strength, high-toughness boron carbide-chromium diboride fired In the process of researching and developing the aggregate, we add a certain amount of chromium diboride to boron carbide powder with specific physical properties, and a liquid phase in which chromium diboride liquid phase is generated under non-pressurized condition By performing sintering and thereby producing a sintered body having a specific microstructure and a highly conductive chromium diboride phase forming a three-dimensional network structure, excellent characteristics are obtained. The inventors have found that a boron carbide-chromium diboride sintered body can be obtained, and have completed the present invention.
[0006]
That is, the present invention has a relative density of 90% or more, a conductivity of 5 × 10 2 S / m or more, a four-point bending strength of 400 MPa or more, and a strength of 3.0 MPa · m 1/2 or more. It is an object of the present invention to provide a boron carbide-chromium diboride sintered body having a fracture toughness value, a method of producing them by sintering them under non-pressing conditions, and an application thereof. is there.
[0007]
[Means for Solving the Problems]
The present invention for solving the above-mentioned problems includes the following technical means.
(1) Liquid phase sintering in which a predetermined amount of a chromium diboride powder is added to a boron carbide powder and mixed to form a raw material powder, and then a liquid phase of the chromium diboride is generated under a non-pressurized condition. And producing a sintered body in which the chromium diboride phase forms a three-dimensional network structure.
(2) The method according to (1), wherein a boron carbide powder having an average particle size (D 50 ) of 2 μm or less and a specific surface area of 10 m 2 / g or more is used.
(3) The method according to (1) above, wherein a chromium diboride powder having an average particle size (D 50 ) of 8 μm or less is used.
(4) The method according to (1), wherein the chromium diboride powder is added to the boron carbide powder in an amount of 10 to 25 mol%.
(5) The method according to (1), wherein the liquid phase sintering is performed by heating to 1950 to 2100 ° C. under a non-pressurizing condition in a non-oxidizing atmosphere.
(6) the boron carbide containing 10 to 25 mol% diboride chromium (CrB 2) the boron carbide (B 4 C) obtained by the method according to any one of (1) to (5) - diboride A chromium sintered body, wherein the relative density of the sintered body is 90% or more, the maximum particle diameter of the boron carbide particles in the sintered body is 100 μm or less, and the boron carbide particles having a particle diameter of 5 μm or less. A boron carbide-chromium diboride sintered body, wherein the abundance ratio (area ratio) of boron carbide particles of 10 to 100 μm is 0.02 to 0.6.
(7) The boron carbide-chromium diboride sintered body according to (6), having a conductivity of 5 × 10 2 S / m or more.
(8) The boron carbide-chromium diboride sintered body according to (6), wherein the four-point bending strength is 400 MPa or more and the fracture toughness value is 3.0 MPa · m 1/2 or more.
(9) A boron carbide-chromium diboride sintered body containing 10 to 25 mol% of chromium diboride in the boron carbide according to any of (6) to (8) above, as a constituent element. Wear-resistant member.
[0008]
Embodiment of the present invention
Next, the present invention will be described in more detail.
To produce a dense boron carbide-based sintered body by sintering under non-pressurized conditions, a certain amount of boron carbide grain growth is required. No solidification is obtained. On the other hand, if the grain growth proceeds too much, the coarse particles hinder densification, and the density of the sintered body decreases, and the coarse particles serve as a fracture starting point to lower the bending strength. In the present invention, sintering is performed under specific non-pressurized conditions in a temperature range in which a liquid phase containing chromium diboride (CrB 2 ) as a main component is generated using boron carbide powder having specific physical properties. Thus, the maximum particle diameter of the boron carbide particles is 100 μm or less, and the abundance ratio (area ratio) of the boron carbide particles of 10 to 100 μm to the boron carbide particles of 5 μm or less is in the range of 0.02 to 0.6. The chromium diboride phase having a relative density of 90% or more and having high conductivity forms a three-dimensional network structure, has a conductivity of 5 × 10 2 S / m or more, and has a conductivity of 400 MPa or more. , And a fracture toughness value of 3.0 MPa · m 1/2 or more, thereby producing a boron carbide-chromium diboride sintered body.
[0009]
The boron carbide powder used in the present invention preferably has an average particle diameter (D 50 ) of 2 μm or less as measured by a laser diffraction scattering method or a Doppler method. If the average particle size (D 50 ) is larger than 2 μm, the sinterability is poor, and a dense sintered body cannot be obtained in a temperature range of 1950 to 2100 ° C. In order to densify the sintered body, grain growth tends to occur. It is necessary to sinter at a higher temperature, which may lead to deterioration of bending strength. As for the specific surface area (BET), it is preferable to use a boron carbide powder having a good sinterability of 10 m 2 / g or more, and more preferably 15 m 2 / g or more.
[0010]
The boron carbide powder having the above-mentioned properties can be prepared by means such as sieving, sedimentation, and pulverization, but a commercially available product having the above-mentioned properties may be obtained and used.
After adding 10 to 25 mol% of chromium diboride powder to the boron carbide powder having the above physical properties and molding, sintering at 1950 to 2100 ° C. under vacuum or under non-pressurizing conditions in a non-oxidizing atmosphere such as Ar. Heating (sintering) is performed in a temperature range while a chromium diboride-based liquid phase is generated.
[0011]
Chromium diboride powder reacts with some boron carbide powder during sintering and melts to generate a chromium diboride-based liquid phase, which penetrates between boron carbide particles. A raw material powder having a large particle size can be used, and a chromium diboride powder having an average particle size (D 50 ) of 8 μm or less can be used, and more preferably an average particle size (D 50 ) of 4 μm can be used. The following can be used:
[0012]
When the sintering temperature is lower than 1950 ° C., a chromium diboride-based liquid phase is not generated, so that a sufficiently dense boron carbide sintered body cannot be produced, and a three-dimensional network of the chromium diboride phase is formed. No structure is formed, and therefore high conductivity cannot be obtained. At a sintering temperature higher than 2100 ° C., coarse boron carbide particles are generated by grain growth, which may cause a decrease in bending strength.
[0013]
If the addition amount of chromium diboride is less than 10 mol%, a sufficient amount of chromium diboride-based liquid phase is not generated, so that a dense sintered body cannot be obtained, and the conductivity and the fracture toughness value are improved. The effect is not enough. When the addition amount of chromium diboride is more than 25 mol%, the density of the sintered body becomes 3. It becomes higher than 0 g / cm 3 , and the light weight characteristics of the boron carbide based sintered body are impaired, and the hardness is also reduced. The boron carbide-chromium diboride sintered body produced by the method of the present invention has excellent characteristics and is useful as a wear-resistant member. In the present invention, the above-mentioned wear-resistant member is meant to include all kinds of members such as sliding parts, cutting tools, and wear-resistant parts.
[0014]
[Action]
In the present invention, a liquid phase sintering in which a liquid phase of chromium diboride is generated under non-pressurized conditions is performed to form a chromium diboride phase having a specific microstructure and high conductivity in a three-dimensional manner. By producing a sintered body having a network structure formed thereon, a boron carbide-chromium diboride sintered body having excellent characteristics can be produced. In the boron carbide-chromium diboride sintered body of the present invention, since the thermal expansion coefficient of chromium diboride is larger than that of boron carbide, cracks occur near the interface between the boron carbide particles and the chromium diboride phase during the progress of fracture. The toughness of the fracture is improved due to the detour of the propagation of the signal and the occurrence of the micro clock. Further, the maximum particle size is 100 μm or less, the protrusions of the boron carbide particles disappear due to the dissolution / precipitation mechanism by the chromium diboride-based liquid phase, stress concentration is reduced, and the boron carbide particles Since they are bonded by the chromium oxide phase, the strength is improved by suppressing the dropout of boron carbide particles during processing and the fracture toughness value is improved, so that a high bending strength of 400 MPa or more can be obtained.
[0015]
【Example】
Hereinafter, the content of the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.
Example 1
20 mol% of chromium diboride powder having an average particle diameter (D 50 ) of 3.5 μm was mixed with boron carbide powder I having the physical properties shown in Table 1, and the mixture was rotated by a planetary ball mill made of SiC using a methanol solvent. Number: 275 rpm, mixing for 1 hour was performed. The slurry was dried by an evaporator, further dried at 150 ° C. for 24 hours, and then passed through a 250 mesh sieve to prepare a boron carbide-chromium diboride mixed powder. After the die was molded at 20 MPa, CIP molding at 200 MPa was performed to produce a molded body. The compact was placed in a graphite container and attached to a resistance heating sintering furnace. 1. Using a diffusion pump 0 × 10 −1 to 2. While evacuating to a pressure of 0 × 10 −2 Pa, heating was performed at a heating rate of 40 ° C./min. When the temperature reached 1000 ° C., the evacuation was terminated, Ar gas was introduced, and the mixture was heated to 1500 ° C. Heating was performed at a rate of 10 ° C./min from 1500 ° C. to 2030 ° C. After the temperature reached 2030 ° C., sintering was performed for 1 hour under a non-pressurized condition to produce a boron carbide-chromium diboride sintered body.
[0016]
[Table 1]
The four-point bending strength and the fracture toughness value of the boron carbide sintered body were measured based on JIS R1601 and JIS R1607, respectively. The surface of the test piece was finished with a surface grinder No. 400. Further, the density of the test piece was measured by the Archimedes method, and the relative density was calculated. After lapping the surface of the test piece and performing an etching treatment, SEM observation and image processing are performed to obtain a maximum particle diameter of boron carbide, and boron carbide of 10 to 100 μm with respect to boron carbide particles having a particle diameter of 5 μm or less. The abundance ratio (area ratio) of the particles was measured. The conductivity was measured using a four-terminal method.
[0018]
Table 2 shows the results of the evaluation. The obtained sintered body has a relative density of 90% or more, a maximum particle diameter of 100 μm or less, an abundance ratio (area ratio) of boron carbide particles in a range of 0.02 to 0.6, It had a conductivity of 5 × 10 2 S / m or more, a four-point bending strength of 400 MPa or more, and a fracture toughness of 3.0 MPa · m 1/2 or more.
[0019]
[Table 2]
Example 2
20 mol% of chromium diboride powder having an average particle diameter (D 50 ): 3.5 μm was mixed with boron carbide powder II having the physical properties shown in Table 1, and the mixture was rotated with a SiC planetary ball mill using a methanol solvent. Number: 275 rpm, mixing for 1 hour was performed. The slurry was dried by an evaporator, further dried at 150 ° C. for 24 hours, and then passed through a 250 mesh sieve to prepare a boron carbide-chromium diboride mixed powder. After the die was molded at 20 MPa, CIP molding at 200 MPa was performed to produce a molded body. The compact was placed in a graphite container and attached to a resistance heating sintering furnace. 1. Using a diffusion pump 0 × 10 −1 to 2. While evacuating to a pressure of 0 × 10 −2 Pa, heating was performed at a heating rate of 40 ° C./min. When the temperature reached 1000 ° C., the evacuation was terminated, Ar gas was introduced, and the mixture was heated to 1500 ° C. Heating was performed at a rate of 10 ° C./min from 1500 ° C. to 2030 ° C. After the temperature reached 2030 ° C., sintering was performed for 1 hour under a non-pressurized condition to produce a boron carbide-chromium diboride sintered body.
[0021]
The four-point bending strength and the fracture toughness value of the boron carbide sintered body were measured based on JIS R1601 and JIS R1607, respectively. The surface of the test piece was finished with a surface grinder No. 400. Further, the density of the test piece was measured by the Archimedes method, and the relative density was calculated. After lapping the surface of the test piece and performing an etching treatment, SEM observation and image processing are performed to obtain a maximum particle diameter of boron carbide, and boron carbide of 10 to 100 μm with respect to boron carbide particles having a particle diameter of 5 μm or less. The abundance ratio (area ratio) of the particles was measured. The conductivity was measured using a four-terminal method.
[0022]
Table 2 shows the results of the evaluation. The obtained sintered body has a relative density of 90% or more, a maximum particle diameter of 100 μm or less, an abundance ratio (area ratio) of boron carbide particles in a range of 0.02 to 0.6, It had a conductivity of 5 × 10 2 S / m or more, a four-point bending strength of 400 MPa or more, and a fracture toughness of 3.0 MPa · m 1/2 or more.
[0023]
Comparative Example 1
Sintering was carried out under non-pressurized conditions in the same procedure as in Examples 1 and 2 except that boron carbide powder III having the physical properties shown in Table 1 was used to obtain boron carbide-chromium diboride. A sintered body was prepared and evaluated.
Table 2 shows the results of the evaluation. In Comparative Example 1, since a boron carbide powder having an average particle diameter (D 50 ) of more than 2 μm and a specific surface area (BET) of less than 10 m 2 / g was used, a dense sintered body could not be obtained, and The abundance ratio (area ratio) deviated from the range of 0.02 to 0.6, and the bending strength and the fracture toughness value were low.
[0024]
Example 3
15 mol% of the same chromium diboride powder as in Examples 1 and 2 was added to boron carbide powder I, and a boron carbide-chromium diboride mixed powder was prepared in the same procedure as in Examples 1 and 2 above. did. Sintering was performed under non-pressurized conditions in the same procedure as in Examples 1 and 2 except that the sintering temperature was 2050 ° C. to produce a boron carbide-chromium diboride sintered body, and the evaluation was performed. went.
Table 2 shows the results of the evaluation. The obtained sintered body has a relative density of 90% or more, a maximum particle diameter of 100 μm or less, an abundance ratio (area ratio) of boron carbide particles in a range of 0.02 to 0.6, It had a conductivity of 5 × 10 2 S / m or more, a four-point bending strength of 400 MPa or more, and a fracture toughness of 3.0 MPa · m 1/2 or more.
[0025]
Example 4
22.5 mol% of the same chromium diboride powder as in Examples 1 and 2 was added to boron carbide powder I, and the mixture of boron carbide and chromium diboride was mixed in the same procedure as in Examples 1 and 2. Was prepared. Sintering was performed under non-pressurized conditions in the same procedure as in Examples 1 and 2 except that the sintering temperature was set to 2020 ° C. to produce a boron carbide-chromium diboride sintered body, and the evaluation was performed. went.
Table 2 shows the results of the evaluation. The obtained sintered body has a relative density of 90% or more, a maximum particle diameter of 100 μm or less, an abundance ratio (area ratio) of boron carbide particles in a range of 0.02 to 0.6, It had a conductivity of 5 × 10 2 S / m or more, a four-point bending strength of 400 MPa or more, and a fracture toughness of 3.0 MPa · m 1/2 or more.
[0026]
Comparative Example 2
Sintering was carried out under non-pressurized conditions in the same procedure as in Examples 1 and 2 except that the blending amount of the chromium diboride powder was 7.5 mol%, and boron carbide-diboride was obtained. A chromium sintered body was prepared and evaluated.
Table 2 shows the results of the evaluation. Since the blending amount of the chromium diboride powder is low and a sufficient amount of the chromium diboride-based liquid phase is not generated, a dense sintered body cannot be obtained, and the abundance ratio (area ratio) of the boron carbide particles is 0. 0.02 to 0.6, the conductivity was not improved, and the flexural strength and fracture toughness were low.
[0027]
【The invention's effect】
As described in detail above, the present invention relates to a boron carbide-chromium diboride sintered body and a method for producing the same. According to the present invention, 1) a highly conductive chromium diboride phase is three-dimensionally formed. 2) The boron carbide-chromium diboride sintered body of the present invention is heated (sintered) under a non-pressurized condition (normal pressure method) at a low sintering temperature. 3) It has a high sintered body density, has good conductivity, and can be processed by electric discharge machining, and 4) provides a new wear-resistant member. Furthermore, 5) The boron carbide-chromium diboride sintered body of the present invention has high strength and toughness and excellent mechanical properties, so that sliding parts, cutting tools, new wear-resistant parts, etc. It can be used in various applications and has a special effect of being industrially useful. That.
Claims (9)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2003092454A JP3926760B2 (en) | 2002-05-07 | 2003-03-28 | Boron carbide-chromium diboride sintered body and method for producing the same |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2002131272 | 2002-05-07 | ||
| JP2003092454A JP3926760B2 (en) | 2002-05-07 | 2003-03-28 | Boron carbide-chromium diboride sintered body and method for producing the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2004026633A true JP2004026633A (en) | 2004-01-29 |
| JP3926760B2 JP3926760B2 (en) | 2007-06-06 |
Family
ID=31190079
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2003092454A Expired - Lifetime JP3926760B2 (en) | 2002-05-07 | 2003-03-28 | Boron carbide-chromium diboride sintered body and method for producing the same |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3926760B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7557054B2 (en) | 2006-02-27 | 2009-07-07 | Kyocera Corporation | Boron carbide sintered body and protective member |
-
2003
- 2003-03-28 JP JP2003092454A patent/JP3926760B2/en not_active Expired - Lifetime
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7557054B2 (en) | 2006-02-27 | 2009-07-07 | Kyocera Corporation | Boron carbide sintered body and protective member |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3926760B2 (en) | 2007-06-06 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US7442661B2 (en) | Boron carbide based sintered compact and method for preparation thereof | |
| JP4854482B2 (en) | Boron carbide sintered body and manufacturing method thereof | |
| KR101160140B1 (en) | Manufacturing method of zirconium diboride-silicon carbide composite | |
| JPH0662338B2 (en) | Silicon carbide / Graphite / Carbon composite ceramic body | |
| JP6344844B2 (en) | Boron carbide / titanium boride composite ceramics and method for producing the same | |
| JP5692845B2 (en) | Highly rigid ceramic material and manufacturing method thereof | |
| JP2002003276A (en) | Reaction synthesis of silicon carbide-boron nitride composite material | |
| JP3686029B2 (en) | Boron carbide-titanium diboride sintered body and manufacturing method thereof | |
| JP4913468B2 (en) | Silicon carbide polishing plate and method for polishing semiconductor wafer | |
| JP3926760B2 (en) | Boron carbide-chromium diboride sintered body and method for producing the same | |
| JP5673946B2 (en) | Method for producing silicon nitride ceramics | |
| JP5093433B2 (en) | Method for producing a bulk body of Al-added TiN | |
| JP3561476B2 (en) | Boron carbide-chromium diboride sintered body and method for producing the same | |
| JP4612608B2 (en) | Method for producing silicon / silicon carbide composite material | |
| JP3992474B2 (en) | Method for producing boron carbide-aluminum nitride sintered body | |
| JP2001247366A (en) | Boron carbide sintered compact and method for producing the same | |
| JP2004292176A (en) | Combined ceramic and and method of manufacturing the same | |
| JP2005082815A (en) | Highly thermal conductive wear resistant material, and its production method | |
| JPH05178657A (en) | Alumina group composite sintered body and its production | |
| JP7470294B2 (en) | Sintered diamond thermal diffusion material and its manufacturing method | |
| JP2007326745A (en) | Wear resistant member, wear resistant equipment and method of manufacturing wear resistant member | |
| JP2023046932A (en) | Manufacturing method of composite ceramic | |
| JP2004189524A (en) | Method of manufacturing silicon carbide fine particles-dispersed ceramic sintered compact | |
| JP2007055897A (en) | Silicon/silicon carbide composite material | |
| JPH09295869A (en) | Sialon ceramic excellent in impact resistance and its production |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A711 | Notification of change in applicant |
Free format text: JAPANESE INTERMEDIATE CODE: A711 Effective date: 20041013 |
|
| RD02 | Notification of acceptance of power of attorney |
Free format text: JAPANESE INTERMEDIATE CODE: A7422 Effective date: 20041013 |
|
| A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A821 Effective date: 20041014 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20050922 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20060908 |
|
| A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20061107 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20061218 |
|
| A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20070207 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20070223 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20070228 |
|
| R150 | Certificate of patent or registration of utility model |
Ref document number: 3926760 Country of ref document: JP Free format text: JAPANESE INTERMEDIATE CODE: R150 Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20100309 Year of fee payment: 3 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20110309 Year of fee payment: 4 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120309 Year of fee payment: 5 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120309 Year of fee payment: 5 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20130309 Year of fee payment: 6 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20130309 Year of fee payment: 6 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20140309 Year of fee payment: 7 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| S533 | Written request for registration of change of name |
Free format text: JAPANESE INTERMEDIATE CODE: R313533 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| S531 | Written request for registration of change of domicile |
Free format text: JAPANESE INTERMEDIATE CODE: R313531 |
|
| S533 | Written request for registration of change of name |
Free format text: JAPANESE INTERMEDIATE CODE: R313533 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| S111 | Request for change of ownership or part of ownership |
Free format text: JAPANESE INTERMEDIATE CODE: R313117 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| EXPY | Cancellation because of completion of term |