JP3550420B2 - Wear-resistant silicon nitride sintered body, method for producing the same, and cutting tool - Google Patents
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Description
【０００１】
【産業上の利用分野】
本発明は、粒界相量が非常に少ないにもかかわらず、相対密度が高く、且つ耐摩耗性に優れた窒化珪素質焼結体（以下、焼結体ということもある。）及びその製造方法、並びに該焼結体からなる切削工具に関する。本発明の焼結体は、切削工具、耐摩耗工具、耐摩耗部品、摺動部品等に利用できる。
【０００２】
【従来の技術】
窒化珪素質焼結体は耐熱性及び耐摩耗性等に優れることから、従来より各種の切削工具用材料などとして使用されている。しかし、窒化珪素は難焼結性のため通常は焼結助剤を使用し焼成されており、この助剤量が多い場合は焼結体の性能が低下するため、焼成が可能な範囲で助剤量は少ない方が好ましい。このため、助剤の種類、使用量の低減等種々観点から性能向上が図られている。例えば、
（１）特開平２−７４５６４号公報及び特開平４−１５４６６９号公報には、Ｍｇ、Ｚｒ、Ｃｅの酸化物等の助剤を従来に比べ少量用いて製造される強度、靱性等の機械的特性或いは耐摩耗性に優れた切削工具用焼結体が開示されている。
【０００３】
（２）焼結助剤を使用せず、ガラス封入によりＨＩＰ焼結し焼結体を得る方法も知られている。
更に、焼成雰囲気に関する技術として、
（３）特開平５−１５５６６２号公報には、微量のＡｌ化合物を添加することにより、焼結性が向上し、他の助剤成分の添加量を減らすことができ、しかも耐摩耗性に優れた焼結体が記載されている。
また、特開昭６２−２７５０６８号公報には、ＣＯ２とＣＯの混合ガスを含む雰囲気中で焼成することにより、雰囲気中の酸素分圧を高め、ガラス相として有効に作用するＳｉＯ２の蒸発等を防止する技術が開示されている。
【０００４】
【発明が解決しようとする課題】
しかし、上記（１）では耐摩耗性等は未だ十分ではなく、助剤量の更なる低減が必要であり、（２）は製造コストが高いため工具材料用焼結体の製造方法としては採用されておらず、また、（３）では焼結性を向上させるためＡｌ２Ｏ３等のＡｌ化合物が使用されているが、これでは焼結体の熱伝導性が低下し、切削加工時に工具がより高温となり耐摩耗性が不十分となる。
以上のように種々の技術開発がなされているものの、切削工具、耐摩耗部品等においては、その工具或いは部品の寿命と密接に関連する耐摩耗性のより一層の向上が要求されている。
本発明は、上記問題点を解決するものであり、特定の元素を酸化物換算で極めて少量含む耐摩耗性に優れた切削工具用窒化珪素質焼結体、及びその焼結体を特定のガス雰囲気中で焼成して製造する方法、並びに該焼結体からなる切削工具を提供することを目的とする。
【０００５】
【課題を解決するための手段】
本発明者らは、耐摩耗性を向上させるには粒界ガラス相量を低減することが有効であることに着目し、低助剤量の窒化珪素質焼結体原料を焼結させる方法を検討した結果、Ｍｇ、Ｚｒ、Ｃｅ、Ｏ、Ｎ元素を粒界成分とするガラス相或いは結晶相からなる焼結体において、焼成雰囲気中にＭｇＯガス等を含ませること及びＣＯガスをある特定の範囲以下に制御することで、低助剤量で焼成でき、且つ耐摩耗性等に優れた焼結体を得ることができることを見出し、本発明を完成するに至った。
【０００６】
即ち、本第１発明の切削工具用窒化珪素質焼結体は、Ｓｉ３Ｎ４を主体とする粒子からなる相と、該粒子の粒界に形成される粒界相とからなる焼結体において、上記焼結体を１００重量％とした場合に、上記Ｓｉ３Ｎ４は９８．０〜９９．９重量％であり、上記粒界相は、ＭｇＯ、ＺｒＯ２及びＣｅＯ２換算でそれぞれ０．０５重量％〜０．５重量％、且つ、合計量が１．５重量％未満であるＭｇ、Ｚｒ並びにＣｅを含むガラス相又は結晶相（但しＡｌは含まない。）であり、カーボンを含有すると共に上記焼結体中のカーボン量が０．２重量％以下であることを特徴とする。また、第２発明の焼結体は、上記粒界相は、Ｉｎ、Ｔａ及びＴｉのうち少なくとも１種を、Ｉｎ２Ｏ３、Ｔａ２Ｏ３並びにＴｉ２Ｏ３換算で、上記焼結体を１００重量％とした場合に、その合計量で０．５重量％以下含むことを特徴とする。
【０００７】
更に、第３発明の焼結体は、上記焼結体の相対密度が９８％以上であり、特定の測定方法による逃げ面摩耗量ＶＢが１．３ｍｍ以下、及び耐欠損性が１０枚以上のうちのどちらかを具備していることを特徴とし、第４発明の焼結体は、上記焼結体の熱伝導率が２５Ｗ／ｍＫ以上、上記焼結体中のカーボン量が０．１５重量％以下であり、第３発明と同じ測定方法による逃げ面摩耗量ＶＢが１．２ｍｍ以下、及び耐欠損性が９枚以上のうちのどちらかを具備していることを特徴とする。
また、第５発明の切削工具は、本発明の焼結体からなることを特徴とする。
【０００８】
上記「Ｓｉ３ Ｎ４ 」相を形成するための原料粉末としては、不純物としての酸素量が１〜３％程度であり、その他の不純物は極く少なく、また、α−Ｓｉ３ Ｎ４ の割合の大きい、一般に原料粉末として好ましいとされているものを特に制限されることなく使用できる。「Ｍｇ」、「Ｚｒ」、「Ｃｅ」成分の原料粉末は、比表面積４ｍ２ ／ｇ以上のものが好ましく、酸化物又は焼成過程で酸化物に変化し得るもの、例えば炭酸塩などの塩或いは水酸化物などが用いられる。
上記「粒界相」はＭｇ、Ｚｒ、Ｃｅ、Ｏ、Ｎ等の元素を含むガラス相又は結晶相からなり、Ｍｇ、Ｚｒ及びＣｅそれぞれの量がＭｇＯ、ＺｒＯ２ 、ＣｅＯ２ 換算で０．０５〜０．５重量％である。この量が０．０５未満では焼結性が不十分であり、０．５重量％を越える場合は耐摩耗性が低下する。また、その合計量は１．５重量％未満であり、合計量がこれを越える場合は耐摩耗性が低下する。
【０００９】
第６発明の耐摩耗性窒化珪素質焼結体の製造方法は、焼結体全体を１００重量％とした場合に、９８．０〜９９．９重量％の窒化珪素と、ＭｇＯ、ＺｒＯ２及びＣｅＯ２換算でそれぞれ０．０５〜０．５重量％、且つその合計量が１．５重量％未満であるＭｇ、Ｚｒ並びにＣｅを含むガラス相又は結晶相である粒界相とからなり、カーボンを含有すると共に上記焼結体中のカーボン量が０．２重量％以下である焼結体を製造するに際し、ＭｇＯガス及び／又はＭｇガス含み、且つ０．１体積％未満のＣＯガスを含む焼成雰囲気中で焼成することを特徴とする。
【００１０】
上記「ＭｇＯガス及び／又はＭｇガス含む」焼成雰囲気とするためには、例えばサヤ中に窒化珪素成形体とともにＭｇＯ焼結体を入れ加熱すればよい。これによりその時のＣＯ濃度、温度等の条件により、両ガスがそれぞれ単独で或いは共存の形で雰囲気中に存在することになる。使用するＭｇＯ焼結体の量は窒化珪素成形体との重量比で０．５％以上が好ましい。これ未満の量では窒化珪素成形体からのＭｇＯの揮散を十分抑えることができず、粒界相を形成するためのＭｇ成分が下限量未満となって焼結性が損なわれることがある。また、本発明の方法では、同時に「焼成雰囲気中のＣＯガスの量を０．１体積％未満」とすることにより実施されるが、ＣＯガスがこれ以上の量である場合は、窒化珪素成形体中のＳｉＯ２ の還元反応による揮散量が増加し、粒界相形成に有効な作用をするＳｉＯ２ の減少により焼結性が大きく低下する。
【００１１】
本発明の方法では、ＭｇＯガス等を含む焼成雰囲気とし、且つ雰囲気中のＣＯガスの量は０．１体積％未満に制御されるが、これにより焼結性はより一層向上し、得られる焼結体の耐摩耗性等の性能も更に向上する。
また、ＣＯガスを制御することにより炭素の生成が抑えられ、得られる焼結体中の炭素含有量は０．２重量％以下と低く抑えられ、これによっても耐摩耗性等が向上するため好ましい。
焼成は、常圧焼成或いは常圧焼成を行った後、二次焼成として雰囲気加圧焼成を行い実施することができる。焼成温度は常圧焼成、雰囲気加圧焼成ともに１５００〜２０００℃の範囲とし、二次焼成は１０気圧以上の窒素分圧を有する加圧雰囲気中で行う。雰囲気加圧焼成は熱間静水圧プレス焼結（ＨＩＰ）、ガス圧焼結（ＧＰＳ）等いずれの方法であってもよい。
【００１２】
【作用】
切削中の工具の刃先温度は被切削材や切削条件によって異なるが、通常８００℃を越える高温である。このため耐摩耗性を向上させるためには耐熱性及び耐食性等に優れていなければならず、窒化珪素に比べてこれら特性が劣る粒界相の量を、焼結性が損なわれない範囲で低減する必要がある。本発明では、焼結助剤としてＭｇ、Ｚｒ及びＣｅの化合物を極く少量使用し、これら３元素とＳｉ、Ｎ、Ｏからなる粒界相とすることにより、上記耐摩耗性と焼結性とを両立させたものである。また、Ｍｇ、Ｚｒ、Ｃｅ、Ｎ及びＯ元素を粒界相として含む焼結体は、焼成雰囲気中のＭｇＯガス等及びＣＯガス量によって焼結性が著しく変化するが、本発明の方法では、焼成時の雰囲気を最適化したことにより、極く微量の焼結助剤で焼結が可能となったものである。
【００１３】
【実施例】
以下、実施例及び比較例により本発明を具体的に説明する。
下記の各原料粉末を使用し、表１（実験例１〜１７）及び表２（比較実験例１８〜２８）に示す割合で配合し焼結体を得た。
▲１▼Ｓｉ３ Ｎ４ 粉末：平均粒径；０．７μｍ、α率；９８％、比表面積；１０ｍ２ ／ｇ
▲２▼ＭｇＯ粉末：比表面積；４ｍ２ ／ｇ
▲３▼ＺｒＯ２ 粉末：比表面積；１４ｍ２ ／ｇ
▲４▼ＣｅＯ２ 粉末：比表面積；８ｍ２ ／ｇ
▲５▼Ｔａ２ Ｏ５ 粉末：比表面積；８ｍ２ ／ｇ
▲６▼Ｃｒ２ Ｏ３ 粉末：比表面積；８ｍ２ ／ｇ
▲７▼Ｉｎ２ Ｏ３ 粉末：比表面積；同９ｍ２ ／ｇ
【００１４】
【表１】
【表２】
尚、表１中の実験Ｎｏ．１３〜１７の、その他の添加物は不純物として存在しても影響がないものの例であり、熱伝導率を低下させるＡｌ２ Ｏ３ との比較として使用したものである。但し、Ｉｎ、Ｔａ、Ｔｉの酸化物は、焼結性を向上させる効果があるため選択したものである。また、表１及び表２中のサヤ中のＭｇＯ焼結体の量は、窒化珪素成形体を焼成する際に成形体とともにサヤ中に入れたＭｇＯ焼結体の窒化珪素成形体に対する重量百分率を表す。
【００１７】
焼結体は、先ず乾燥した配合粉末を２ｔｏｎ／ｃｍ２ の圧力で金型プレス成形し、その後、ＭｇＯガス等を含む窒素ガス雰囲気中、１気圧、１６００〜１９００℃で２時間一次焼成を行い、次いで、一時焼成と同様のガス雰囲気中、１００気圧、１８００〜２０００℃で２時間二次焼成を行って製造した。尚、一時及び二次焼成ともに、サヤ中に窒化珪素成形体とともにＭｇＯ焼結体を入れることにより上記特定のガス雰囲気とすることができる。
得られた焼結体について、切削工具としての耐摩耗性及び耐欠損性を測定した結果を表３に示す。
【００１８】
【表３】
以下に各特性の測定方法を示す。
１）相対密度：
アルキメデス法により焼結体密度を測定し、以下の式より相対密度を算出した。
相対密度（％）＝（焼結体密度／同組成の完全緻密焼結体密度）×１００
２）熱伝導率：
焼結体の８００℃における熱伝導度をレーザーフラッシュ法により測定した。試片の大きさは直径）ｍｍ、厚さ１ｍｍの円板形状とした。
３）カーボン量：
焼結体のカーボン量は燃焼法により測定した。
【００２０】
４）耐摩耗性
ＳＮＧＮ４３２、チャンファー０．１５のチップを用い、被削材としてＦＣ２３、２４０ｍｍφ×１００ｍｍＬを選び、切削速度３００ｍ／ｍｉｎ、切込み１．５ｍｍ、送り速度０．３ｍｍ／ｒｅｖ及び切削長さ４００ｍｍの条件でフランク摩耗量を測定し、逃げ面摩耗量ＶＢ とした。
５）耐欠損性
ＳＮＧＮ４３２、チャンファー０．０７のチップを用い、被削材としてＦＣ２３を選び、切削速度１５０ｍ／ｍｉｎ、切込み２．０ｍｍ、送り速度０．８ｍｍ／ｒｅｖの条件で、外形２００ｍｍ、厚さ１１ｍｍの円板の外側面を軸方向に切削し、欠損が生じるまでの円板の枚数を測定した。
【００２１】
表３の結果から、各実験例の焼結体は耐摩耗性ＶＢ が１．３ｍｍ以下、又は欠損が生じるまでの円板枚数が１０枚以上のうちのどちらかの性能を有しており、切削特性に優れたものであることが分かる。これに対して比較実験例１８は助剤成分の合計が２重量％であるため、十分緻密化しているにもかかわらず（相対密度＝１００％）、耐摩耗性、耐欠損性ともにやや低い数値となっており、切削特性が劣っている。比較実験例２１は助剤量が比較的少量であるうえに、焼成雰囲気中のＣＯガス量が上限を越えているため、一次焼成後の密度が低く緻密化できず、相対密度が８９％未満と低い。
【００２２】
また、焼結助剤としてＩｎ、Ｔｉ、Ｔａの各成分を併用した実験例１３〜１７においても、十分な性能の焼結体が得られているが、同様に併用した比較実験例２２〜２５では耐欠損性は優れるものの耐摩耗性が劣っている。更に、Ａｌ２ Ｏ３ を添加した比較実験例２６では、熱伝導率が低下したことにより耐摩耗性が低下している。これらの結果により、本発明の窒化珪素質焼結体は従来の焼結体に比較し優れた耐摩耗性と耐欠損性とを併せ持つものであることが分かる。
尚、本発明においては、前記具体的実施例に示すものに限られず、目的、用途に応じて本発明の範囲内で種々変更した実施例とすることができる。
【００２３】
【発明の効果】
第１発明の窒化珪素質焼結体は、粒界相が特定の極く少量の成分からなっており、それにもかかわらず焼結性に優れ、相対密度が実質的に１００％の極めて緻密な焼結体であり、第２発明によれば、粒界相中にＭｇ、Ｚｒ及びＣｅ成分以外に、少量のＩｎ、Ｔａ並びにＴｉのうち少なくとも１種を含んでいても、第１発明とまったく同様に焼結性及び耐摩耗性に優れた焼結体が得られる。また、第３発明及び第４発明の焼結体は、相対密度並びに逃げ面摩耗量ＶＢ 、耐欠損性のうちの少なくともいずれかが非常に優れたものであり、また、焼結体中のカーボン量が第１〜第３発明では０．２重量％以下、第４発明では０．１５重量％以下であって、この点も耐摩耗性の向上に寄与するものである。よって、本発明の焼結体は、第５発明のように、切削工具に好適に用いることができる。更に、第６発明の方法によれば、焼成雰囲気中にＭｇＯガス等を存在させ、且つＣＯガスの量を特定することにより、複雑な装置、手順等を要することなく、耐摩耗性、耐欠損性等の切削特性に優れた焼結体を得ることができる。[0001]
[Industrial applications]
The present invention provides a silicon nitride-based sintered body (hereinafter, sometimes referred to as a sintered body) having a high relative density and excellent wear resistance despite having a very small grain boundary phase amount, and its production. And a cutting tool comprising the sintered body . The sintered body of the present invention can be used for cutting tools, wear-resistant tools, wear-resistant parts, sliding parts, and the like.
[0002]
[Prior art]
Silicon nitride-based sintered bodies have been conventionally used as various cutting tool materials because of their excellent heat resistance and wear resistance. However, since silicon nitride is difficult to sinter, it is usually fired using a sintering aid. If the amount of this aid is large, the performance of the sintered body is reduced. The smaller the amount of the agent, the better. For this reason, the performance has been improved from various viewpoints, such as reduction in the type and amount of the auxiliary agent. For example,
(1) JP-A-2-74564 and JP-A-4-154669 disclose mechanical properties such as strength and toughness produced by using a small amount of an auxiliary agent such as oxides of Mg, Zr, and Ce as compared with conventional ones. A sintered body for a cutting tool having excellent characteristics or wear resistance is disclosed.
[0003]
(2) A method of obtaining a sintered body by performing HIP sintering by glass sealing without using a sintering aid is also known.
Furthermore, as a technology related to the firing atmosphere,
(3) JP-A-5-155662 discloses that by adding a small amount of an Al compound, the sinterability is improved, the amount of other auxiliary components to be added can be reduced, and the abrasion resistance is excellent. A sintered body is described.
Japanese Patent Application Laid-Open No. Sho 62-275068 discloses that by baking in an atmosphere containing a mixed gas of CO 2 and CO, the oxygen partial pressure in the atmosphere is increased, and the evaporation of SiO 2 effectively acting as a glass phase. A technique for preventing such a situation has been disclosed.
[0004]
[Problems to be solved by the invention]
However, in (1) above, the abrasion resistance and the like are not yet sufficient, and it is necessary to further reduce the amount of the auxiliary agent. (2) Since the production cost is high, it is adopted as a method for producing a sintered body for tool material. However, in (3) , an Al compound such as Al 2 O 3 is used to improve the sinterability. At a higher temperature, resulting in insufficient wear resistance.
Although various technical developments have been made as described above, cutting tools, wear-resistant parts, and the like are required to have further improved wear resistance closely related to the life of the tools or parts.
The present invention solves the above-mentioned problems, and comprises a silicon nitride-based sintered body for a cutting tool, which contains a very small amount of a specific element in terms of oxide and has excellent wear resistance, and a method for converting the sintered body to a specific gas. It is an object of the present invention to provide a method of manufacturing by firing in an atmosphere, and a cutting tool made of the sintered body .
[0005]
[Means for Solving the Problems]
The present inventors have noticed that it is effective to reduce the amount of the grain boundary glass phase in order to improve the wear resistance, and have sintered a method of sintering a silicon nitride-based sintered material having a low auxiliary amount. As a result of the examination, in a sintered body composed of a glass phase or a crystal phase containing Mg, Zr, Ce, O, and N elements as grain boundary components, it is necessary to include a MgO gas or the like in a firing atmosphere and to use a specific CO gas. It has been found that by controlling the amount to be less than the range, a sintered body that can be fired with a small amount of auxiliary agent and that is excellent in wear resistance and the like can be obtained, and the present invention has been completed.
[0006]
That is, the silicon nitride sintered body for a cutting tool of the first invention is a sintered body composed of a phase composed mainly of Si 3 N 4 and a grain boundary phase formed at the grain boundary of the particles. In the above, when the sintered body is 100% by weight, the Si 3 N 4 is 98.0 to 99.9% by weight, and the grain boundary phase is 0 in terms of MgO, ZrO 2 and CeO 2 respectively. 0.055% by weight to 0.5% by weight, and a glass phase or a crystal phase (but not Al) containing Mg, Zr and Ce having a total amount of less than 1.5% by weight , and containing carbon. And the amount of carbon in the sintered body is 0.2% by weight or less . Further, in the sintered body of the second invention, the grain boundary phase includes at least one of In, Ta, and Ti in terms of In 2 O 3 , Ta 2 O 3 , and Ti 2 O 3. Is set to 100% by weight, the total amount is 0.5% by weight or less.
[0007]
Further, the sintered body of the third invention has a relative density of the sintered body is 98% or more, 1.3mm or less flank wear V B according to specific measurement methods, and chipping resistance than ten Wherein the thermal conductivity of the sintered body is at least 25 W / mK and the amount of carbon in the sintered body is 0.15 or more. or less by weight%, the third invention and flank wear V B by the same measuring method is 1.2mm or less, and fracture resistance, characterized in that it comprises either one of the above nine.
A cutting tool according to a fifth aspect of the present invention is characterized in that the cutting tool is made of the sintered body of the present invention.
[0008]
The raw material powder for forming the “Si 3 N 4 ” phase has an oxygen content of about 1 to 3% as an impurity, has very few other impurities, and has a proportion of α-Si 3 N 4 . A powder having a large value and generally preferred as a raw material powder can be used without any particular limitation. The raw material powder of the “Mg”, “Zr”, and “Ce” components preferably has a specific surface area of 4 m 2 / g or more, and may be an oxide or a material that can be changed to an oxide in a firing process, for example, a salt such as a carbonate or the like. A hydroxide or the like is used.
The “grain boundary phase” is composed of a glass phase or a crystal phase containing elements such as Mg, Zr, Ce, O, and N, and the amount of each of Mg, Zr, and Ce is 0.05 in terms of MgO, ZrO 2 , and CeO 2. ~ 0.5% by weight. If the amount is less than 0.05, the sinterability is insufficient, and if it exceeds 0.5% by weight, the wear resistance is reduced. Further, the total amount is less than 1.5% by weight, and when the total amount exceeds this, the wear resistance is reduced.
[0009]
In the method for producing a wear-resistant silicon nitride-based sintered body according to the sixth aspect of the present invention, 98.0 to 99.9% by weight of silicon nitride, MgO, ZrO 2 and 0.05 wt%, respectively calculated as CeO 2, Ri and Do from the total amount Mg is less than 1.5 wt%, and Zr as well as the grain boundary phase is a glass phase or a crystal phase containing Ce, upon carbon content in the sintered body as well as containing carbon to produce der Ru sintered body 0.2 wt% or less, it comprises MgO gas and / or Mg gas, and less than 0.1 vol% CO gas Characterized by firing in a firing atmosphere containing
[0010]
In order to make the above-mentioned firing atmosphere containing “MgO gas and / or Mg gas”, for example, an MgO sintered body is put in a sheath together with a silicon nitride molded body and heated. Thus, depending on the conditions such as the CO concentration and the temperature at that time, both gases are present in the atmosphere independently or coexisting. The amount of the MgO sintered body used is preferably 0.5% or more by weight ratio with respect to the silicon nitride molded body. If the amount is less than this, the volatilization of MgO from the silicon nitride molded body cannot be sufficiently suppressed, and the Mg component for forming the grain boundary phase is less than the lower limit amount, so that the sinterability may be impaired. In the method of the present invention, the amount of CO gas in the firing atmosphere is set to less than 0.1% by volume at the same time. The amount of volatilization due to the reduction reaction of SiO 2 in the body increases, and the sinterability is greatly reduced due to the decrease in SiO 2 , which works effectively for forming the grain boundary phase.
[0011]
In the method of the present invention, a firing atmosphere containing MgO gas or the like is used, and the amount of CO gas in the atmosphere is controlled to less than 0.1% by volume. The performance such as abrasion resistance of the aggregate is further improved.
Further, by controlling the CO gas, the generation of carbon is suppressed, and the carbon content in the obtained sintered body is suppressed to as low as 0.2% by weight or less, which also improves wear resistance and the like, which is preferable. .
The firing can be performed by performing normal pressure firing or normal pressure firing, and then performing atmospheric pressure firing as secondary firing. The firing temperature is in the range of 1500 to 2000 ° C. for both normal pressure firing and atmospheric pressure firing, and the secondary firing is performed in a pressurized atmosphere having a nitrogen partial pressure of 10 atm or more. Atmospheric pressure sintering may be any method such as hot isostatic press sintering (HIP) and gas pressure sintering (GPS).
[0012]
[Action]
The cutting edge temperature of the tool during cutting varies depending on the material to be cut and cutting conditions, but is usually a high temperature exceeding 800 ° C. For this reason, in order to improve wear resistance, it must be excellent in heat resistance and corrosion resistance, etc., and the amount of the grain boundary phase, which is inferior to silicon nitride, is reduced to the extent that sinterability is not impaired. There is a need to. In the present invention, by using a very small amount of a compound of Mg, Zr and Ce as a sintering aid and forming a grain boundary phase composed of these three elements and Si, N and O, the above-mentioned wear resistance and sintering property are obtained. And both. Further, a sintered body containing Mg, Zr, Ce, N and O elements as grain boundary phases has a remarkable change in sinterability depending on the amount of MgO gas or the like and the amount of CO gas in the firing atmosphere. By optimizing the atmosphere during sintering, sintering can be performed with a very small amount of sintering aid.
[0013]
【Example】
Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.
The following raw material powders were used and blended at the ratios shown in Table 1 (Experimental Examples 1 to 17) and Table 2 (Comparative Experimental Examples 18 to 28) to obtain sintered bodies.
{Circle around (1)} Si 3 N 4 powder: average particle size: 0.7 μm, α ratio: 98%, specific surface area: 10 m 2 / g
{Circle around (2)} MgO powder: specific surface area: 4 m 2 / g
{Circle around (3)} ZrO 2 powder: specific surface area; 14 m 2 / g
{Circle around (4)} CeO 2 powder: specific surface area: 8 m 2 / g
(5) Ta 2 O 5 powder: specific surface area: 8 m 2 / g
{Circle around (6)} Cr 2 O 3 powder: specific surface area: 8 m 2 / g
{Circle around (7)} In 2 O 3 powder: specific surface area: 9 m 2 / g
[0014]
[Table 1]
[Table 2]
In Table 1, the experiment No. Other additives 13 to 17 are examples of those having no effect even if present as impurities, and were used as a comparison with Al 2 O 3 which lowers the thermal conductivity. However, oxides of In, Ta, and Ti are selected because they have an effect of improving sinterability. In Tables 1 and 2, the amount of the MgO sintered body in the sheath is the weight percentage of the MgO sintered body put in the sheath together with the molded body when the silicon nitride molded body is fired with respect to the silicon nitride molded body. Represent.
[0017]
For the sintered body, first, the dried compounded powder is press-molded at a pressure of 2 ton / cm 2 and then subjected to primary firing at 1 atm and 1600 to 1900 ° C. for 2 hours in a nitrogen gas atmosphere containing MgO gas or the like. Then, secondary baking was performed at 100 atm and 1800 to 2000 ° C. for 2 hours in the same gas atmosphere as the temporary baking. In both the temporary and secondary firing, the specific gas atmosphere can be set by putting an MgO sintered body together with the silicon nitride molded body in the sheath.
Table 3 shows the results of measuring the wear resistance and fracture resistance of the obtained sintered body as a cutting tool.
[0018]
[Table 3]
The measuring method of each characteristic is shown below.
1) Relative density:
The sintered body density was measured by the Archimedes method, and the relative density was calculated from the following equation.
Relative density (%) = (density of sintered body / density of perfect dense sintered body of the same composition) × 100
2) Thermal conductivity:
The thermal conductivity at 800 ° C. of the sintered body was measured by a laser flash method. The size of the specimen was a disk having a diameter of 1 mm and a thickness of 1 mm.
3) Carbon content:
The amount of carbon in the sintered body was measured by a combustion method.
[0020]
4) Wear resistance Using a tip of SNGN432 and a chamfer of 0.15, FC23, 240 mmφ × 100 mmL was selected as a work material, a cutting speed of 300 m / min, a cutting depth of 1.5 mm, a feed speed of 0.3 mm / rev, and a cutting length. the flank wear amount were measured under the conditions of the 400 mm, and the flank wear V B.
5) Using a chip of fracture resistance SNGN432 and a chamfer of 0.07, FC23 was selected as a work material, a cutting speed of 150 m / min, a cutting depth of 2.0 mm, and a feed speed of 0.8 mm / rev. The outer surface of a disk having a thickness of 11 mm was cut in the axial direction, and the number of disks until a defect occurred was measured.
[0021]
The results in Table 3, the sintered body of each of the experimental examples are abrasion resistance V B is 1.3mm or less, or disc number until defects occurs has either performance of 10 or more It can be seen that the cutting characteristics were excellent. On the other hand, in Comparative Experimental Example 18, since the total amount of the auxiliary components was 2% by weight, although it was sufficiently densified (relative density = 100%), both the wear resistance and the fracture resistance were slightly lower. And the cutting characteristics are inferior. In Comparative Experimental Example 21, the amount of the auxiliary agent was relatively small, and the amount of CO gas in the sintering atmosphere exceeded the upper limit. Therefore, the density after the first sintering was too low to be densified, and the relative density was less than 89%. And low.
[0022]
Further, in Experimental Examples 13 to 17 in which the respective components of In, Ti, and Ta were used in combination as sintering aids, sintered bodies having sufficient performance were obtained. Although the fracture resistance is excellent, the wear resistance is inferior. Furthermore, in Comparative Experimental Example 26 in which Al 2 O 3 was added, the abrasion resistance was reduced due to the reduced thermal conductivity. From these results, it can be seen that the silicon nitride sintered body of the present invention has both excellent wear resistance and chipping resistance as compared with conventional sintered bodies.
It should be noted that the present invention is not limited to the specific embodiments described above, but may be variously modified within the scope of the present invention in accordance with the purpose and application.
[0023]
【The invention's effect】
The silicon nitride-based sintered body of the first invention has a very fine grain boundary phase composed of a specific extremely small amount of components, and yet has excellent sinterability and a relative density of substantially 100%. According to the second invention, even if the grain boundary phase contains a small amount of at least one of In, Ta, and Ti in addition to the Mg, Zr, and Ce components, the sintered body is completely different from the first invention. Similarly, a sintered body having excellent sinterability and wear resistance can be obtained. Further, the sintered body of the third invention and the fourth invention, the relative density and flank wear VB, are those least one of chipping resistance is excellent, Carbon in sintered body The amount is 0.2% by weight or less in the first to third inventions and 0.15% by weight or less in the fourth invention, which also contributes to the improvement of the wear resistance. Therefore, the sintered body of the present invention can be suitably used for a cutting tool as in the fifth invention. Furthermore, according to the method of the sixth invention, the abrasion resistance and chipping resistance can be achieved without requiring complicated devices and procedures by specifying MgO gas or the like in the firing atmosphere and specifying the amount of CO gas. It is possible to obtain a sintered body having excellent cutting characteristics such as the workability.
Claims (6)
上記焼結体を１００重量％とした場合に、上記Ｓｉ３Ｎ４は９８．０〜９９．９重量％であり、上記粒界相は、ＭｇＯ、ＺｒＯ２及びＣｅＯ２換算でそれぞれ０．０５〜０．５重量％、且つその合計量が１．５重量％未満であるＭｇ、Ｚｒ並びにＣｅを含むガラス相又は結晶相（但しＡｌは含まない。）であり、カーボンを含有すると共に上記焼結体中のカーボン量が０．２重量％以下であることを特徴とする耐摩耗性窒化珪素質焼結体。In a sintered body composed of a phase composed mainly of particles of Si 3 N 4 and a grain boundary phase formed at the grain boundary of the particles,
When the sintered body is 100% by weight, the content of Si 3 N 4 is 98.0 to 99.9% by weight, and the grain boundary phase is 0.05% in terms of MgO, ZrO 2 and CeO 2 respectively. 0.5 wt%, and Mg total amount thereof is less than 1.5 wt%, the glass phase or a crystal phase containing Zr and Ce (where Al is not included.) der is, the addition to containing carbon carbon content the wear resistance of silicon nitride sintered material, characterized in der Rukoto 0.2 wt% or less in the sintered body.
逃げ面摩耗量ＶＢ：ＳＮＧＮ４３２、チャンファー０．１５のチップを使用、被削材；ＦＣ２３、２４０ｍｍφ×１００ｍｍＬ、切削速度；３００ｍ／ｍｉｎ、切込み；１．５ｍｍ、送り速度；０．３ｍｍ／ｒｅｖ、切削長さ；４００ｍｍ 耐欠損性：ＳＮＧＮ４３２、チャンファー０．０７のチップを使用、被削材；ＦＣ２３、切削速度；１５０ｍ／ｍｉｎ、切込み；２．０ｍｍ、送り速度；０．８ｍｍ／ｒｅｖの条件で、外形２００ｍｍ、厚さ１１ｍｍの円板の外側面を軸方向に切削した場合の欠損が生じるまでの円板の枚数The relative density of the sintered body is 98% or more, less flank wear V B is 1.3mm according to the following measuring method, and claims chipping resistance is provided with either of the 10 or more Item 3. A wear-resistant silicon nitride-based sintered body according to item 1 or 2.
Flank wear V B: SNGN432, using chip chamfer 0.15, workpiece; FC23,240mmφ × 100mmL, cutting speed; 300 meters / min, cut; 1.5 mm, feed rate; 0.3 mm / rev , Cutting length: 400 mm Fracture resistance: Using a chip of SNGN432, chamfer 0.07, Work material: FC23, Cutting speed: 150 m / min, Cutting depth: 2.0 mm, Feeding speed: 0.8 mm / rev Under conditions, the number of discs until a defect occurs when the outer surface of a disc having an outer shape of 200 mm and a thickness of 11 mm is cut in the axial direction.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP08566394A JP3550420B2 (en) | 1994-03-30 | 1994-03-30 | Wear-resistant silicon nitride sintered body, method for producing the same, and cutting tool |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP08566394A JP3550420B2 (en) | 1994-03-30 | 1994-03-30 | Wear-resistant silicon nitride sintered body, method for producing the same, and cutting tool |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH07267738A JPH07267738A (en) | 1995-10-17 |
| JP3550420B2 true JP3550420B2 (en) | 2004-08-04 |
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| JP08566394A Expired - Lifetime JP3550420B2 (en) | 1994-03-30 | 1994-03-30 | Wear-resistant silicon nitride sintered body, method for producing the same, and cutting tool |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2008114752A1 (en) | 2007-03-22 | 2008-09-25 | Ngk Spark Plug Co., Ltd. | Insert and cutting tool |
| US11865624B2 (en) | 2018-08-28 | 2024-01-09 | Kyocera Corporation | Insert and cutting tool |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3042402B2 (en) * | 1996-04-26 | 2000-05-15 | 住友電気工業株式会社 | Silicon nitride ceramic sliding material and method for producing the same |
| WO1999044937A1 (en) * | 1998-03-05 | 1999-09-10 | International Business Machines Corporation | Material with reduced optical absorption |
| JP4541477B2 (en) * | 1999-12-28 | 2010-09-08 | 日本特殊陶業株式会社 | Silicon nitride sintered body, tool and sliding member using the same, and method for producing silicon nitride sintered body |
-
1994
- 1994-03-30 JP JP08566394A patent/JP3550420B2/en not_active Expired - Lifetime
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2008114752A1 (en) | 2007-03-22 | 2008-09-25 | Ngk Spark Plug Co., Ltd. | Insert and cutting tool |
| US8492300B2 (en) | 2007-03-22 | 2013-07-23 | Ngk Spark Plug Co., Ltd. | Insert and cutting tool |
| US11865624B2 (en) | 2018-08-28 | 2024-01-09 | Kyocera Corporation | Insert and cutting tool |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH07267738A (en) | 1995-10-17 |
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