JP7068658B2 - Hard sintered body and its manufacturing method - Google Patents
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Description
本発明は、高硬度、高強度かつ高融点セラミックとして知られるＷＣ（炭化タングステン）粒子を硬質相とし、前記ＷＣと親和性にすぐれたＷ２Ｃとを有する焼結体およびその製造方法に関するものである。
本発明に係る焼結体は、高温硬度ならびに高温強度にすぐれ、また、緻密性や破壊靱性特性にもすぐれるため、切削工具の刃先材料あるいは高温で使用される金型などの耐摩耗工具材料としても用いることができる。
The present invention relates to a sintered body having WC (tungsten carbide) particles known as high hardness, high strength and high melting point ceramic as a hard phase and having W2C having excellent affinity with the WC and a method for producing the same. Is.
The sintered body according to the present invention is excellent in high-temperature hardness and high-temperature strength, and also has excellent fineness and fracture toughness characteristics. Can also be used as.
ＷＣを使った硬質焼結体として、Ｃｏを金属結合相とする焼結体がよく知られている。
しかしながら、常温域においては、ＷＣとＣｏは十分な結合力を持たないため、ＷＣとＣｏの境界が破壊の起点となるなど脆弱さに問題を有していた。
また、金属結合相を有する焼結体では、切削時の刃先温度がより高温になる焼入れ鋼の切削や重切削の用途、あるいは化学装置などで耐腐食性が要求されるシールリングなどの用途において、高温での硬度や耐食性に対する課題も生じていた。
As a hard sintered body using WC, a sintered body having Co as a metal bonding phase is well known.
However, in the normal temperature range, since WC and Co do not have a sufficient bonding force, there is a problem of vulnerability such that the boundary between WC and Co becomes the starting point of fracture.
In addition, in a sintered body having a metal bonding phase, it is used for cutting hardened steel and heavy cutting where the cutting edge temperature at the time of cutting becomes higher, or for sealing rings where corrosion resistance is required in chemical equipment. There were also problems with hardness and corrosion resistance at high temperatures.
これに対し、例えば、特許文献１によれば、結合相としてＣｏを用いず、Ｗを用い、ＷＣを硬質相とする焼結体は、英国特許第５０４，５２２号にて紹介されており、具体的には、ＷＣ６０％～８０％と、Ｗ１５％～３５％および／またはＭｏ７％～２３％と、微量のＣｏ、Ｓｉ、Ｂとから成る混合粉を１６．５ＭＰａの圧力下１７５０℃～１９００℃において焼結することにより得られるとされている。
しかしながら、特許文献１では、そこで得られた焼結体は、低硬度で脆く、その原因はＷの大部分が低硬度、低強度であるＷ２Ｃに変態したためであるとし、同文献では、かかる課題を解決すべく、具体的な製造方法として、１８重量％または１０体積％のＷと、残部がフィッシャー法（ＦＳＳＳ）により測定された平均粒径（ＦＳＳＳ粒径）が０．２５μｍを有するＷＣとからなる粉末混合物を湿式粉砕、乾燥後、１８００℃にて３０ＭＰａでホットプレスした後、アルゴンガス中１２００℃にて８時間処理することが提案されている。
そして、かかる製造方法により得られた硬質材料は、室温における硬度（ＨＶ）においてすぐれ、Ｘ線回折パターンにおけるピーク比でＷ２Ｃ（１０１）／Ｗ（１１０）が０．３未満であり、すぐれた切削性を有する切削工具インサートが得られたとしている。
On the other hand, for example, according to Patent Document 1, a sintered body in which Co is not used as the bonding phase, W is used, and WC is used as a hard phase is introduced in British Patent No. 504,522. Specifically, a mixed powder consisting of
However, in Patent Document 1, the sintered body obtained there is low hardness and brittle, and the cause is that most of W is transformed into W 2 C having low hardness and low strength. In order to solve this problem, as a specific manufacturing method, W has 18% by weight or 10% by volume, and the balance has an average particle size (FSSS particle size) measured by the Fisher method (FSSS) of 0.25 μm. It has been proposed that a powder mixture composed of WC is wet-ground, dried, hot-pressed at 1800 ° C. at 30 MPa, and then treated in argon gas at 1200 ° C. for 8 hours.
The hard material obtained by such a manufacturing method is excellent in hardness (HV) at room temperature, and W2 C (101) / W (110) is less than 0.3 in the peak ratio in the X-ray diffraction pattern, which is excellent. It is said that a cutting tool insert with excellent machinability was obtained.
本発明において原料として用いられるＷやＷＣは、いずれも、融点が３３００℃以上の高融点材料として知られ、かつ耐食性においてもすぐれており、これらを含む焼結体の作製には、１５００℃以上の高温での焼成が必要である。
しかしながら、図１のＷ－ＷＣ状態図（D.K.Gupta and L.LSeigle; Metallurgical TransactionsA , vol.6A (1975) p.1941を参照。）において示すとおり、１４００℃～１４５０℃以上の温度領域では炭素を含有していると低硬度、低強度のＷ２Ｃが生成することとなるため、ＷおよびＷＣ系の焼結体においては、低硬度、低強度のＷ２Ｃの生成を極力抑制することが課題であった。
なお、表１と表２には、Ｗ、ＷＣ、Ｗ２Ｃそれぞれの物性値及び機械特性値を示すが、表２からも明らかなとおり、Ｗ２Ｃの硬度は、ＷＣに対し、４５％程度劣っている。（表１は、化学大辞典５、縮刷版第３４刷、化学大辞典編集委員会編集、共立出版株式会社から、表２は、特開平１１－７９８３９号公報の表１から引用したものである。）
Both W and WC used as raw materials in the present invention are known as high melting point materials having a melting point of 3300 ° C. or higher, and are also excellent in corrosion resistance. It is necessary to bake at a high temperature.
However, as shown in the W-WC phase diagram of FIG. 1 (see DKGupta and L.LSeigle; Metallurgical TransactionsA, vol.6A (1975) p.1941), carbon is contained in the temperature range of 1400 ° C to 1450 ° C or higher. If this is the case, low hardness and low strength W 2 C will be generated. Therefore, in the W and WC based sintered bodies, it is a problem to suppress the formation of low hardness and low strength W 2 C as much as possible. Met.
Tables 1 and 2 show the physical property values and mechanical property values of W, WC, and W 2 C, respectively. As is clear from Table 2, the hardness of W 2 C is 45% of that of WC. Inferior in degree. (Table 1 is taken from Chemistry Encyclopedia 5, reduced edition 34th edition, edited by the Chemistry Encyclopedia Editorial Committee, Kyoritsu Shuppan Co., Ltd. , and Table 2 is taken from Table 1 of JP-A No. 11-79839. .)
このような課題に関して、特許文献１では、前記したとおり、二段階の熱処理、すなわち、まず、第一段階の熱処理では、結合相として高融点金属のタングステンを用いることに伴い、１５００℃を越えた温度にて圧密化し、Ｗ２Ｃを相当量生成するものの空隙の少ない組織を得て、その後、第二段階の熱処理としては、１２５０℃の不活性雰囲気あるいは真空中にて熱処理を行い、Ｗ２ＣをＷとＷＣに再変態させることにより、Ｗ２Ｃ含有量を低減させることができたとしている。
しかしながら、特許文献１に記載された方法を用いることによっても、依然として、Ｗ２Ｃは残存しており、しかも、前記した熱処理では、組織中のＷ２Ｃの分散や大きさを制御することが困難であるため、焼結体中に粗大で低強度のＷ２Ｃが残ることとなり、このような組織を有する焼結体を工具として使用した場合に、高負荷下の条件では、Ｗ２Ｃが破壊の起点として働くため、大幅な寿命の短縮が発生するという問題があった。
そこで、本発明は、Ｗ２ＣとＷＣを含む焼結体において、Ｗ２Ｃ粒子の粒径を微粒とし焼結体組織中に微細分散させた組織を得て、さらに、焼結時に微粒なＷＯ２
粒子を生成させ、焼結体組織中に微細分散させることにより、硬度、強度、耐破壊靱性、緻密性、及び耐食性にすぐれ、切削用工具の刃先材料にとどまらず、高温にて使用される金型などの耐摩耗性材料として用いるほか、シールリング等の用途にも使用可能な焼結体およびその製造方法を提供することを目的としてなされたものである。
Regarding such a problem, as described above, in Patent Document 1, in the two-step heat treatment, that is, first, in the first-step heat treatment, the temperature exceeds 1500 ° C. due to the use of tungsten, which is a refractory metal, as the bonding phase. Tungsten at a temperature to obtain a structure that produces a considerable amount of W 2 C but has few voids. Then, as the second stage heat treatment, heat treatment is performed in an inert atmosphere at 1250 ° C. or in a vacuum, and W 2 It is said that the W2C content could be reduced by retransforming C into W and WC.
However, even by using the method described in Patent Document 1, W 2 C still remains, and the heat treatment described above can control the dispersion and size of W 2 C in the structure. Since it is difficult, coarse and low-strength W 2 C remains in the sintered body, and when a sintered body having such a structure is used as a tool, under high load conditions, W 2 C remains. Since it works as a starting point of destruction, there is a problem that the life is significantly shortened.
Therefore, in the present invention, in a sintered body containing W 2 C and WC, a structure is obtained in which the particle size of the W 2 C particles is made fine and finely dispersed in the sintered body structure, and further, the fine particles are obtained at the time of sintering. By generating WO 2 particles and finely dispersing them in the structure of the sintered body, it has excellent hardness, strength, fracture resistance, compactness, and corrosion resistance, and is used not only as a cutting tool material for cutting tools but also at high temperatures. The purpose of the present invention is to provide a sintered body that can be used as an abrasion-resistant material for molds and the like, and can also be used for applications such as sealing rings, and a method for manufacturing the sintered body.
そして、本発明は、高硬度、高強度かつ高融点の炭化物として知られるＷＣ粒子からなる硬質相と、前記ＷＣと親和性にすぐれたＷ２Ｃ粒子を有する焼結体において、強度の低下を招く粗大なＷ２Ｃの生成を抑制する新たな手段を見出すことにより、高硬度、高強度、緻密性、及び、耐食性にすぐれた焼結体を得たものであり、さらには、原料粉末表面へ付与する酸素を制御し、表面の酸素とＷとを反応させて得られる微粒ＷＯ２を組織中に微細分散させ、Ｗ２Ｃ粒子およびＷＣ粒子の粒成長を抑制し、焼結体を微細な粒子からなる組織とするとともに、焼結体内部に生じたクラックの先端を偏向させ進展しにくくすることにより、高硬度、高強度、緻密性、及び、耐食性に加え、破壊靱性特性にもすぐれたきわめて有用な焼結体を提供することにより、前記課題を解決したものである。 The present invention further reduces the strength of a sintered body having a hard phase composed of WC particles known as carbides having high hardness, high strength and high melting point, and W2C particles having excellent affinity with the WC. By finding a new means for suppressing the formation of coarse W2C , a sintered body having excellent hardness, high strength, fineness, and corrosion resistance was obtained, and further, the surface of the raw material powder. Fine particles WO 2 obtained by reacting surface oxygen and W are finely dispersed in the structure, the grain growth of W 2C particles and WC particles is suppressed, and the sintered body is made fine. The structure is made up of fine particles, and the tips of cracks generated inside the sintered body are deflected to make it difficult for them to grow. By providing a very useful sintered body, the above-mentioned problems are solved.
すなわち、低強度であるＷ２Ｃの生成の制御については、種々の製造条件を工夫することにより見出したものであって、例えば、原料粉末であるＷ粉末及びＷＣ粉末としては、ナノサイズ化した微細なものであって、凝集性が低く、不純物混入の少ない粉末を用い、それぞれの粒度を適正範囲に調整し、さらに、グラフェンを混合させ、焼結方法としては、前記Ｗ－ＷＣ状態図において、Ｗ２Ｃが安定相として生成する１５５０℃以上２３００℃以下の高温領域での焼結、すなわち、高温焼結法を用いることにより、Ｗ２Ｃを生成させ、さらに、このＷ２ＣはグラフェンとＷ粉末が反応することにより微細なＷ２Ｃ粒子とすることができ、緻密で高硬度及び高強度の焼結体が得られることを見出したものである。その際、必要に応じて、焼結時に加圧するホットプレス法や放電プラズマ焼結法（SPS法）を用いることも有効である。 That is, the control of the formation of W 2 C having low strength was found by devising various production conditions. For example, the raw material powders W powder and WC powder were nano-sized. Using powder that is fine, has low cohesiveness, and has little contamination with impurities, adjust the grain size of each to an appropriate range, mix graphene, and use the W-WC state diagram as the sintering method. , W 2 C is generated as a stable phase in a high temperature region of 1550 ° C. or higher and 2300 ° C. or lower, that is, W 2 C is generated by using a high temperature sintering method, and further, this W 2 C is graphene. It has been found that fine W2C particles can be obtained by reacting with W powder, and a dense, high-hardness and high-strength sintered body can be obtained. At that time, it is also effective to use a hot press method or a discharge plasma sintering method (SPS method) that pressurizes at the time of sintering, if necessary.
さらに原料粉末の表面に付与する酸素量や、グラフェンなど微細な炭素源を適量に制御することにより、焼結時に、微粒のＷＯ２
粒子を生成させ、焼結体組織中に微細分散させることにより、Ｗ２Ｃ粒子およびＷＣ粒子の粒成長を抑制し、また焼結体内部に生じたクラックの先端を偏向させ進展しにくくすることにより焼結体の破壊靱性特性の向上を実現したものである。
すなわち、本発明において用いるナノサイズ粉末においては、表面積が増える分、表面の清浄度は重要となり、表面の清浄度が悪い場合には、Ｗ粒子やＷＣ粒子表面の反応性が悪くなり、Ｗ２Ｃ粒子とＷＣ粒子との密着性が悪化する。また、ここで、表面清浄度の高いＷ粉末を用いた場合、ＷＣ粒子とＷ粒子の反応性が高くなり、焼結時に粒成長し易く、粗大なＷ２Ｃ粒子が生じてしまうという課題を有していた。
Furthermore, by controlling the amount of oxygen applied to the surface of the raw material powder and a fine carbon source such as graphene to an appropriate amount, fine WO2 particles are generated at the time of sintering and finely dispersed in the sintered body structure. , W2C particles and WC particles are suppressed from growing, and the tips of cracks generated inside the sintered body are deflected to make it difficult for them to grow, thereby improving the fracture toughness characteristics of the sintered body. ..
That is, in the nano-sized powder used in the present invention, the cleanliness of the surface becomes important as the surface area increases, and when the cleanliness of the surface is poor, the reactivity of the surface of W particles and WC particles becomes poor, and W 2 The adhesion between the C particles and the WC particles deteriorates. Further, when W powder having a high surface cleanliness is used, there is a problem that the reactivity between the WC particles and the W particles becomes high, the particles easily grow during sintering, and coarse W 2 C particles are generated. Had had.
そこで、本発明は、かかる課題について、Ｗ原料粉の表面の酸素量を調整するとともに、原料中にグラフェンをあらかじめ混合することにより、ＷＣ粉末表面の酸素とグラフェンとの反応により、ＷＣ粉末の表面が清浄化し、ＷＣ粉末の反応を高めＷＣ粒子と接する他の粒子との密着性が高い焼結体となるだけでなく、またＷ原料粉にあらかじめ付与した酸素とＷ粉末との反応により、ＷＯ２
粒子を生成させ、かつグラフェンはＷ粉末と反応することにより微細なＷ２Ｃ粒子となり、この微粒なＷ２Ｃ粒子とＷＯ２
粒子を焼結体組織中に微細分散させることにより、微細な組織とすることで、破壊靱性値の高い焼結体を実現したものである。
グラフェンを原料に用いた場合、微細なＷ２Ｃ粒子が生成することに関しては、シート状で厚みがナノオーダーと薄いグラフェンは混合した際に薄くＷＣ粒子やＷ粒子表面に付着しやすく、Ｗ粒子に関して、ＷＯ２
粒子が生成した後に露出したＷ粉末の表面でグラファイトと反応することにより微細なＷ２Ｃ粒子となり、また近傍のＷＯ２
粒子が、生成したＷ２Ｃ粒子同士やＷＣ粒子とＷ粒子との反応によるＷ２Ｃ粒子の生成を阻害し、微細なＷ２Ｃ粒子とＷＯ２
粒子を高分散化することができたことによるものと推論される。
Therefore, the present invention solves this problem by adjusting the amount of oxygen on the surface of the W raw material powder and mixing graphene in the raw material in advance, thereby causing the reaction between the oxygen on the surface of the WC powder and the graphene to cause the surface of the WC powder. Not only does it purify and enhance the reaction of the WC powder to form a sintered body with high adhesion to other particles in contact with the WC particles, but also due to the reaction between the oxygen previously applied to the W raw material powder and the W powder , WO Two particles are generated, and graphene reacts with W powder to become fine W 2 C particles , and these fine W 2 C particles and WO 2 particles are finely dispersed in the sintered structure. By forming the structure, a sintered body with a high fracture toughness value is realized.
When graphene is used as a raw material, fine W2C particles are generated. Graphene, which is sheet-like and has a thickness of nano-order and is thin, tends to adhere to the surface of WC particles and W particles when mixed, and W particles. By reacting with graphite on the surface of the W powder exposed after the formation of WO 2 particles , fine W 2 C particles are formed, and the nearby WO 2 particles are combined with the generated W 2 C particles or WC particles . It is presumed that this is because the formation of W 2 C particles by the reaction with W particles was inhibited and the fine W 2 C particles and WO 2 particles could be highly dispersed.
本発明は、上記の知見に基づいてなされたものであって、
「（１） 硬質相として炭化タングステン（ＷＣ）粒子を５０ｖｏｌ％～９５ｖｏｌ％含有し、結合相としてＷ２Ｃ粒子を４ｖｏｌ％～５０ｖｏｌ％および酸化タングステン（ＷＯ２）を０．５ｖｏｌ％～５．０ｖｏｌ％含有する焼結体であって、
前記Ｗ２Ｃ粒子と前記酸化タングステン（ＷＯ２）粒子は、平均粒径が５ｎｍ以上１５０ｎｍ以下であり、焼結体組織内において、前記酸化タングステン（ＷＯ２
）粒子が５個／μｍ
２ ～４０個／μｍ２の平均密度にて存在することを特徴とする焼結体。
（２） ナノサイズのＷ粉末およびＷＣ粉末と、厚みがナノオーダーであるグラフェンを原料として用い、酸素付与処理を行ったＷ粉末と、グラフェンおよびＷＣ粉末を混合し、圧力５０ＭＰａ～１０ＧＰａ、温度１５５０℃～２３００℃、保持時間５分～１２０分間の条件にて高温高圧焼結を行うことを特徴とする前記（１）に記載された焼結体の製造方法。」
に特徴を有するものである。
The present invention has been made based on the above findings.
"(1) Tungsten carbide (WC) particles are contained in an amount of 50 vol% to 95 vol% as a hard phase, W2 C particles are contained in an amount of 4 vol% to 50 vol% and tungsten oxide (WO 2 ) is contained in an amount of 0.5 vol% as a bonded phase. A sintered body containing ~ 5.0 vol%,
The W 2 C particles and the tungsten oxide (WO 2 ) particles have an average particle size of 5 nm or more and 150 nm or less, and the tungsten oxide ( WO 2 ) particles are 5 particles / μm 2 to 40 in the sintered body structure. A sintered body characterized by being present at an average density of 2 pieces / μm 2 .
(2) Nano-sized W powder and WC powder, graphene having a thickness of nano-order as a raw material, oxygenated W powder, graphene and WC powder are mixed, and the pressure is 50 MPa to 10 GPa and the temperature is 1550. The method for producing a sintered body according to (1) above, wherein high temperature and high pressure sintering is performed under the conditions of ° C. to 2300 ° C. and holding time of 5 minutes to 120 minutes . "
It has the characteristics of.
本発明の構成について、さらに以下にて説明する。
なお、本明細書および特許請求の範囲において、数値範囲を「～」にて表現するとき、その範囲は、上限および下限の数値を含むものである。
The configuration of the present invention will be further described below.
In the present specification and claims, when the numerical range is expressed by "-", the range includes the numerical values of the upper limit and the lower limit.
＜焼結体の成分組成＞
本発明に係る焼結体は、Ｗ２Ｃ粒子、ＷＣ粒子、ＷＯ２
粒子を有し、その成分組成は、以下のとおりである。
Ｗ２Ｃ粒子、ＷＣ粒子：
Ｗ２Ｃ粒子は、４ｖｏｌ％未満では、Ｗ２Ｃの平均粒径をナノサイズにしても、ＷＣ粒子周囲に十分に配置することができず焼結性が悪くなり、緻密な焼結体組織が得られず、他方、５０ｖｏｌ％を超えると硬度が十分でなくなるため、Ｗ２Ｃの含有量を４ｖｏｌ％～５０ｖｏｌ％と規定した。
ＷＣ粒子の含有量は、高硬度を維持するための必要量として、５０ｖｏｌ％～９５ｖｏｌ％とした。
<Component composition of sintered body>
The sintered body according to the present invention has W2C particles , WC particles , and WO2 particles , and the composition thereof is as follows.
W 2 C particles , WC particles :
If the W 2 C particles are less than 4 vol%, even if the average particle size of W 2 C is nano-sized, they cannot be sufficiently arranged around the WC particles and the sinterability deteriorates, resulting in a dense sintered body structure. On the other hand, if the hardness exceeds 50 vol%, the hardness becomes insufficient. Therefore, the W2C content is defined as 4 vol% to 50 vol%.
The content of WC particles was set to 50 vol% to 95 vol% as a necessary amount for maintaining high hardness.
ＷＯ２
粒子：
ＷＯ２
粒子は、焼結体組織の靱性の向上を図るために必要であり、０．５ｖｏｌ％未満では、進展するクラックの先端を偏向し進展しにくくすることができず、焼結体組織の靱性低下につながり、また、５．０ｖｏｌ％を超えると組織中においてＷＯ２
粒子の割合が増加するとともに、ＷＯ２
粒子となる前の酸素が焼結性を悪化させ、結果として焼結体の脆性が増すため、０．５ｖｏｌ％～５．０ｖｏｌ％とした。
WO 2 particles :
WO 2 particles are necessary for improving the toughness of the sintered body structure, and if it is less than 0.5 vol%, the tip of the crack that grows cannot be deflected and made difficult to grow, and the sintered body structure cannot be easily grown. It leads to a decrease in toughness, and when it exceeds 5.0 vol%, the proportion of WO 2 particles in the tissue increases, and oxygen before becoming WO 2 particles deteriorates the sinterability, resulting in brittleness of the sintered body. Therefore, it was set to 0.5 vol% to 5.0 vol%.
上記組成に対し、焼結体のさらなる高硬度化並びに耐酸化性を向上するために、ＷＣ粒子の一部をＴｉ、Ｔａ、Ｖ、Ｍｏ及びＣｒの炭化物および／または炭窒化物に置換することができる。 With respect to the above composition, in order to further increase the hardness and the oxidation resistance of the sintered body, a part of the WC particles is replaced with carbides and / or carbonitrides of Ti, Ta, V, Mo and Cr. Can be done.
＜焼結体組織＞
（１）Ｗ２Ｃ粒子、ＷＣ粒子およびＷＯ２粒子の平均粒径
本発明焼結体組織におけるＷ２Ｃ粒子、ＷＣ粒子およびＷＯ２粒子の平均粒径は、それぞれＷ ２
Ｃ粒子では５ｎｍ～１５０ｎｍ、ＷＣ粒子では２０ｎｍ～９０００ｎｍ、ＷＯ２粒子では、５ｎｍ～１５０ｎｍの範囲とする。
すなわち、焼結後のＷ２Ｃ粒子の平均粒径は、５ｎｍより小さいとＷＣ粒子を保持する効果が少なくなり好ましくなく、１５０ｎｍより大きくなると衝撃要素が多い条件下での使用に際しＷ２Ｃ粒子が変形し易くなり好ましくないためである。
また、焼結後のＷＣ粒子の平均粒径は、２０ｎｍより小さいと焼結体組織中に空隙ができる可能性が高くなり、緻密な焼結体組織を得ることが困難となり好ましくない。他方、９０００ｎｍより大きいと硬さが低い組織となり、高硬度の組織が得られないため、好ましくない。
焼結後のＷＯ２
粒子については、平均粒径が５ｎｍより小さいと、進展するクラックの先端を偏向する効果を低減させ、焼結体の靱性を低下させるため好ましくない。他方、平均粒径が１５０ｎｍより大きいとＷＯ２
粒子自体が破壊の原因となり、焼結体の靱性を低下させるため好ましくない。
（２）ＷＯ２
粒子の焼結体組織中における平均個数密度
また、焼結後のＷＯ２
粒子の焼結体組織中における平均個数密度については、５個／μｍ２より少ないと進展するクラックの先端を偏向し進展しにくくする効果を低減させ、焼結体の靱性を低下させるため、好ましくなく、４０個／μｍ２より多いと進展するクラックの先端を偏向し進展しにくくする効果には十分であるが、組織内にＷＯ２
粒子が占める割合が多くなる結果、焼結体組織の脆性が高まり、靱性が低下するため、５個／μｍ
２ ～４０個／μｍ２の範囲とする。
<Sintered structure>
(1) Average particle size of W 2 C particles, WC particles and WO 2 particles
The average particle size of W 2 C particles, WC particles and WO 2 particles in the sintered body structure of the present invention is 5 nm to 150 nm for W 2 C particles, 20 nm to 9000 nm for WC particles, and 5 nm to 150 nm for WO 2 particles, respectively. The range.
That is, if the average particle size of the W 2 C particles after sintering is smaller than 5 nm, the effect of retaining the WC particles is less preferable, and if it is larger than 150 nm, the W 2 C particles are used under conditions where there are many impact elements. This is because it is not preferable because it is easily deformed.
Further, if the average particle size of the WC particles after sintering is smaller than 20 nm, there is a high possibility that voids are formed in the sintered body structure, and it is difficult to obtain a dense sintered body structure, which is not preferable. On the other hand, if it is larger than 9000 nm, the structure becomes low in hardness and a structure with high hardness cannot be obtained, which is not preferable.
For the WO 2 particles after sintering, if the average particle size is smaller than 5 nm, the effect of deflecting the tip of the growing crack is reduced and the toughness of the sintered body is lowered, which is not preferable. On the other hand, if the average particle size is larger than 150 nm, the WO 2 particles themselves cause fracture and reduce the toughness of the sintered body, which is not preferable.
(2) Average number density of WO 2 particles in the sintered body structure Further, the average number density of WO 2 particles in the sintered body structure after sintering is less than 5 / μm 2 for cracks that grow. It is not preferable because it reduces the effect of deflecting the tip and making it difficult to grow, and lowers the toughness of the sintered body. However, as a result of the large proportion of WO 2 particles in the structure, the brittleness of the sintered structure increases and the toughness decreases, so the range is 5 / μm 2 to 40 / μm 2 .
（３）焼結体中のＷ２Ｃ粒子、ＷＣ粒子、ＷＯ２
粒子の含有量の測定
焼結体中のＷ２Ｃ粒子、ＷＣ粒子、ＷＯ２
粒子の含有量は、走査型電子顕微鏡搭載のエネルギー分散型Ｘ線分析装置（ＳＥＭ－ＥＤＸ）と電子線後方散乱回折法（ＥＢＳＤ）を用い、測定することができる。
すなわち、本発明焼結体の断面組織をＳＥＭにて観察し、二次電子像を得るとともに、ＥＤＸにて同個所のＷ元素とＯ元素のマッピング像を取得し、Ｗ元素とＯ元素が重なる部分をＷＯ２
粒子として、画像処理にて抜き出し、画像解析よってＷＯ２粒子が占める面積を算出し、１画像内の各粒子が占める割合を求め、面積割合をｖｏｌ％と見なし、少なくとも３画像を処理し求めた値の平均値を各粒子の含有量として求める。
画像内の各粒子の部分を画像処理にて抜き出すにあたり、各々の粒子部分を明確に判断するため、画像は０を黒、２５５を白の２５６階調のモノクロで表示する２値化処理像を用いた。
また、断面組織をＥＢＳＤにて観察し、結晶方位マップ像を取得するとともに、結晶構造や格子定数の違いなどの情報からＷ２Ｃ粒子とＷＣ粒子を判別し、各々判別した画像を基に、画像解析によってＷ２Ｃ粒子とＷＣ粒子とが占める面積を算出し、１画像内の各粒子が占める割合を求め、面積割合をｖｏｌ％と見なし、少なくとも３画像を処理し求めた値の平均値を各粒子の含有量として求める。
画像処理に用いる観察領域としては、９．０μｍ×９．０μｍ程度の視野領域が望ましい。
(3) Measurement of the contents of W 2 C particles , WC particles , and WO 2 particles in the sintered body The contents of W 2 C particles , WC particles , and WO 2 particles in the sintered body are equipped with a scanning electron microscope. It can be measured by using the energy dispersive X-ray analyzer (SEM-EDX) and the electron backscatter diffraction method (EBSD).
That is, the cross-sectional structure of the sintered body of the present invention is observed by SEM to obtain a secondary electron image, and a mapping image of W element and O element at the same location is obtained by EDX, and W element and O element overlap. The part is taken as WO 2 particles , extracted by image processing, the area occupied by WO 2 particles is calculated by image analysis, the ratio occupied by each particle in one image is obtained, the area ratio is regarded as vol%, and at least 3 images are obtained. The average value of the values obtained by the treatment is obtained as the content of each particle.
When extracting each particle part in the image by image processing, in order to clearly judge each particle part, the image is a binarized image displaying 0 in black and 255 in white in 256 gradations in monochrome. Using.
In addition, the cross-sectional structure is observed by EBSD to obtain a crystal orientation map image, and W2C particles and WC particles are discriminated from information such as differences in crystal structure and lattice constant, and based on the discriminated images. The area occupied by W2C particles and WC particles is calculated by image analysis, the ratio occupied by each particle in one image is calculated, the area ratio is regarded as vol%, and the average value of the values obtained by processing at least three images is obtained. Is determined as the content of each particle.
As the observation area used for image processing, a visual field area of about 9.0 μm × 9.0 μm is desirable.
（４）焼結体中のＷ２Ｃ粒子、ＷＣ粒子、ＷＯ２
粒子の平均粒径の測定
焼結体中のＷ２Ｃ粒子、ＷＣ粒子、ＷＯ２
粒子の平均粒径は、ＳＥＭ－ＥＤＸとＥＢＳＤを用い、測定することができる。
すなわち、本発明焼結体の断面組織をＳＥＭにて観察し、二次電子像を得るとともに、ＥＤＸにて同個所のＷ元素とＯ元素のマッピング像を取得し、Ｗ元素とＯ元素が重なる部分をＷＯ２
粒子として画像処理にて２値化して抜き出す。
画像内のＷＯ２粒子の部分を画像処理にて抜き出すにあたっては、各々の粒子部分を明確に判断するため、画像は０を黒、２５５を白の２５６階調のモノクロで表示する２値化処理像を用いて行った。
なお、２値化処理後は粒子同士が接触していると考えられる部分を切り離すような処理、例えば画像処理操作の１つであるｗａｔｅｒｓｈｅｄ（ウォーターシェッド）を用いて分離を行う。
２値化処理後に得られた画像内の各粒子にあたる部分（黒の部分）を粒子解析し、求めた最大長を各粒子の最大長とし、それを各粒子の直径として各粒子の体積を計算する。体積は理想球と仮定して計算する。粒子解析を行う際には、あらかじめＳＥＭにより分かっているスケールの値を用いて、１ピクセル当たりの長さ（μｍ）を設定しておく。
各粒子の体積を累積した体積を基に縦軸を体積百分率［％］、横軸を直径［μｍ］としてグラフを描画させ、体積百分率が５０％のときの直径を平均粒径とし、少なくとも３画像から求めた平均値を平均粒径とし、ＷＯ２
粒子の平均粒径（ｎｍ）を得た。
画像処理に用いる観察領域としては、５μｍ×５μｍ程度の視野領域が望ましい。
またＷ２Ｃ粒子とＷＣ粒子に関しては、断面組織をＥＢＳＤにて観察し、結晶方位マップ像を取得するとともに、結晶構造や格子定数の違いなどの情報からＷ２Ｃ粒子とＷＣ粒子を判別し、各々判別した情報を基に、横軸粒径、縦軸面積割合の粒度分布を取得し、Ｄ５０値を平均粒径とし、少なくとも３画像から求めた平均値を平均粒径とし、Ｗ２Ｃ粒子とＷＣ粒子の平均粒径（ｎｍ）を得た。
(4) Measurement of average particle size of W2C particles , WC particles , and WO2 particles in the sintered body The average particle size of W2C particles , WC particles , and WO2 particles in the sintered body is SEM-EDX. And EBSD can be used for measurement.
That is, the cross-sectional structure of the sintered body of the present invention is observed by SEM to obtain a secondary electron image, and a mapping image of W element and O element at the same location is obtained by EDX, and W element and O element overlap. The portion is converted into WO 2 particles by image processing and extracted.
When extracting the WO 2 particle part in the image by image processing, in order to clearly judge each particle part, the image is binarized by displaying 0 in black and 255 in white in 256 gradations in monochrome. It was done using an image.
After the binarization process, separation is performed using a process of separating the portion where the particles are considered to be in contact with each other, for example, watershed, which is one of the image processing operations.
Particle analysis is performed on the part corresponding to each particle (black part) in the image obtained after binarization, the maximum length obtained is set as the maximum length of each particle, and the volume of each particle is calculated using that as the diameter of each particle. do. The volume is calculated assuming an ideal sphere. When performing particle analysis, the length per pixel (μm) is set using the scale value known in advance by SEM.
Based on the accumulated volume of each particle, draw a graph with the vertical axis as the volume percentage [%] and the horizontal axis as the diameter [μm], and the diameter when the volume percentage is 50% is the average particle size, at least 3. The average value obtained from the image was taken as the average particle size , and the average particle size (nm) of WO 2 particles was obtained.
As the observation area used for image processing, a visual field area of about 5 μm × 5 μm is desirable.
For W 2 C particles and WC particles, the cross-sectional structure is observed by EBSD, a crystal orientation map image is acquired, and W 2 C particles and WC particles are discriminated from information such as differences in crystal structure and lattice constant. Based on the information discriminated from each, the particle size distribution of the horizontal axis particle size and the vertical axis area ratio is acquired, the D50 value is used as the average particle size, and the average value obtained from at least three images is used as the average particle size . The average particle size (nm) of the particles and the WC particles was obtained.
（５）焼結体中のＷＯ２
粒子の平均密度（個／μｍ２）および焼結体密度の測定
ＷＯ２粒が焼結体中に存在する密度は、ＳＥＭ－ＥＤＸを用い、測定することができる。すなわち、本発明焼結体の断面組織をＳＥＭにて観察し、二次電子像を得るとともに、ＥＤＸにて同個所のＷ元素とＯ元素のマッピング像を取得し、Ｗ元素とＯ元素が重なる部分をＷＯ２
粒子として画像処理にて２値化して抜き出す。
画像内の各粒子の部分を画像処理にて抜き出すにあたっては、各々の粒子部分を明確に判断するため、画像は０を黒、２５５を白の２５６階調のモノクロで表示する２値化処理像を用いて行った。
なお、２値化処理後はＷＯ２粒子同士が接触していると考えられる部分を切り離すような処理、例えば画像処理操作の１つであるｗａｔｅｒｓｈｅｄ（ウォーターシェッド）を用いて分離を行う。
２値化処理後に得られた画像内のＷＯ２粒子にあたる部分（黒の部分）を粒子解析し、粒子数を算出する。
測定した画像の縦と横の長さから面積を求め、先に算出した粒子数をこの面積にて割ることによりＷＯ２粒子が焼結体中に存在する密度を求め、少なくとも３画像から求めた平均値をＷＯ２
粒子の焼結体中に存在する平均密度（個／μｍ２）とした。
画像処理に用いる観察領域としては、５μｍ×５μｍ程度の視野領域が望ましい。
前記焼結体の観察は、耐摩耗性工具である切削工具の刃先あるいは高温で使用される金型などその用途に応じて適用される部位について行い、例えば、耐摩耗性工具である切削工具の刃先については、用いる焼結体の表面近傍箇所について観察する。
また、焼結体の密度は、アルキメデス法を用いて測定を行い、空気中で測定した試料の質量と水中で測定した試料の質量と水の密度を用いて算出した。水の密度は、測定時の水温より得られる水の密度とした。
(5) Measurement of average density (pieces / μm 2 ) of WO 2 particles in the sintered body and density of the sintered body The density of two WO particles in the sintered body should be measured using SEM-EDX. Can be done. That is, the cross-sectional structure of the sintered body of the present invention is observed by SEM to obtain a secondary electron image, and a mapping image of W element and O element at the same location is obtained by EDX, and W element and O element overlap. The portion is converted into WO 2 particles by image processing and extracted.
When extracting each particle part in the image by image processing, in order to clearly judge each particle part, the image is a binarized image in which 0 is displayed in black and 255 is displayed in white in 256 gradations in monochrome. Was performed using.
After the binarization process, separation is performed using a process of separating the portion where the WO 2 particles are considered to be in contact with each other, for example, watershed, which is one of the image processing operations.
The part corresponding to WO 2 particles (black part) in the image obtained after the binarization process is subjected to particle analysis, and the number of particles is calculated.
The area is obtained from the length and width of the measured image, and the density of WO 2 particles present in the sintered body is obtained by dividing the number of particles calculated earlier by this area, and is obtained from at least 3 images. The average value was taken as the average density (pieces / μm 2 ) present in the sintered body of WO 2 particles .
As the observation area used for image processing, a visual field area of about 5 μm × 5 μm is desirable.
The observation of the sintered body is performed on a part to be applied depending on the application such as the cutting edge of a cutting tool which is an abrasion resistant tool or a mold used at a high temperature, and for example, a cutting tool which is an abrasion resistant tool. As for the cutting edge, observe the vicinity of the surface of the sintered body to be used.
The density of the sintered body was measured using the Archimedes method, and was calculated using the mass of the sample measured in air, the mass of the sample measured in water, and the density of water. The density of water was defined as the density of water obtained from the water temperature at the time of measurement.
（６）焼結体のＸＲＤ測定
本発明に係る焼結体の組織は、前述のとおり、ＳＥＭ－ＥＤＸとＥＢＳＤを用いることにより確認することができるが、ＸＲＤ測定によっても確認することができる。
図２および図３に後述する実施例における本発明焼結体１および本発明焼結体２のＸＲＤチャート図を示す。
図２および図３より明らかなとおり、少なくともＷ２Ｃ、ＷＣ、ＷＯ２以外のピークを確認することはできなかった。
なお、後述の焼結体の製造方法において、混合粉の熱処理を行ったものについては、ＷＯ２の測定ピークは明らかではないが、ＳＥＭ－ＥＤＸとＥＢＳＤにより、ＷＯ２
の存在は確認済みである。
(6) XRD measurement of sintered body The structure of the sintered body according to the present invention can be confirmed by using SEM-EDX and EBSD as described above, but can also be confirmed by XRD measurement.
2 and 3 show XRD charts of the sintered body 1 of the present invention and the sintered body 2 of the present invention in Examples described later.
As is clear from FIGS. 2 and 3, at least peaks other than W2C , WC, and WO2 could not be confirmed.
In the method for producing a sintered body described later, the measurement peak of WO 2 is not clear for the heat-treated mixed powder, but the presence of WO 2 has been confirmed by SEM-EDX and EBSD. ..
＜焼結体の製造方法＞
以下に本発明に係る焼結体の製造方法を具体的に示す。
原料粉末の作製：
原料としては、ナノサイズのＷ粉末およびＷＣ粉末、グラフェンを用いる。
Ｗ粉末としては、例えば、超低水蒸気分圧下における水素還元法を用いて作製された、平均粒径が１４０ｎｍ以下のＷ粉末が良く、好ましくは、５ｎｍ～８０ｎｍのものが良い。
また、ＷＣ粉末の焼結性にすぐれるＷＣ粒子サイズは、Ｗ粉末の平均粒径に応じて、ナノサイズからμｍサイズまで選択することができるが、１５ｎｍ～９０００ｎｍが好ましく、３０ｎｍ～７０００ｎｍがより好ましい。
グラフェンは、厚みが５ｎｍ以下の形状が好ましく、例えばチューブ状で厚みが５ｎｍ以下、チューブ幅が１００ｎｍ以下、長さが１μｍ以下の形状であり、有機溶剤中に分散させた分散液を用いる。
まず、Ｗ粉末の前処理として、作製したＷ粉末の各粒子表面へ酸素を付与させるため、例えば、Ｎ２とＣＯ２の混合雰囲気下へ曝すことにより各Ｗ粒子表面へ均一に酸素を付与させたＷ粉末を作製する。
次に、前記前処理を施したＷ粉末５ｖｏｌ％～５０ｖｏｌ％（６質量％～５５．２質量％）と、ＷＣ粉末５０ｖｏｌ％～９５ｖｏｌ％（４４．８質量％～９３．９質量％）と、前記分散液中のグラフェンとを超硬製容器と超硬製のボールを用い、有機溶剤を用いて湿式混合し、乾燥した。
次に、乾燥後の混合粉末の酸素量を調整するため、例えば、圧力１Ｐａの真空雰囲気下、温度１００℃～１３００℃にて所定時間保持する加熱処理（混合粉の熱処理）を行い、酸素量を調整した原料混合粉末を得た。
上記において、Ｗ粉末のより好ましい平均粒径を５ｎｍ以上と規定したのは、５ｎｍ未満では、凝集性の少ない粉末を作製するのが困難であり、粉末が凝集すると表面へ均一に酸素を付与することが困難になるとともに、凝集部は焼結時に反応性が高いため粒成長を生じやすくなり、結果として焼結体の靭性が低下するおそれが生じるためである。
また、ＷＣ粉末の平均粒径は、小さいほど高硬度の焼結体が得られるが、その場合、ＷＣ粉末の表面積が大きくなり、緻密な焼結体を得るためには、Ｗ粉末を多量に含有させるかＷ粉末の平均粒径を小さくする必要が生じるため、ＷＣ粉末の最適な平均粒径はＷ粉末の平均粒径と含有量から選択した。
なお、それぞれの原料粉の平均粒径は、ナノレベルの粉末に対しては、ＢＥＴ法を用いて、μｍレベルの粉末には、レーザー回折法を用いて測定した。
<Manufacturing method of sintered body>
The method for producing the sintered body according to the present invention is specifically shown below.
Preparation of raw material powder:
Nano-sized W powder, WC powder, and graphene are used as raw materials.
As the W powder, for example, W powder having an average particle size of 140 nm or less, which is produced by a hydrogen reduction method under ultra-low steam partial pressure, is preferable, and 5 nm to 80 nm is preferable.
The WC particle size having excellent sinterability of the WC powder can be selected from nano size to μm size according to the average particle size of the W powder, but is preferably 15 nm to 9000 nm, more preferably 30 nm to 7000 nm. preferable.
The graphene preferably has a shape having a thickness of 5 nm or less, for example, a tubular shape having a thickness of 5 nm or less, a tube width of 100 nm or less, and a length of 1 μm or less, and a dispersion liquid dispersed in an organic solvent is used.
First, as a pretreatment of W powder, in order to impart oxygen to the surface of each particle of the produced W powder, for example, by exposing to a mixed atmosphere of N 2 and CO 2 , oxygen is uniformly imparted to the surface of each W particle. W powder is prepared.
Next, the pretreated W powder 5 vol% to 50 vol% (6% by mass to 55.2% by mass) and the
Next, in order to adjust the oxygen content of the mixed powder after drying, for example, a heat treatment (heat treatment of the mixed powder) of holding the mixed powder at a temperature of 100 ° C. to 1300 ° C. for a predetermined time in a vacuum atmosphere at a pressure of 1 Pa is performed to adjust the oxygen content. Was adjusted to obtain a raw material mixed powder.
In the above, the more preferable average particle size of the W powder is defined as 5 nm or more because it is difficult to prepare a powder having low cohesiveness when the average particle size is less than 5 nm, and when the powder agglomerates, oxygen is uniformly applied to the surface. This is because the agglomerated portion is highly reactive at the time of sintering, so that grain growth is likely to occur, and as a result, the toughness of the sintered body may decrease.
Further, the smaller the average particle size of the WC powder, the higher the hardness of the sintered body, but in that case, the surface area of the WC powder becomes large, and in order to obtain a dense sintered body, a large amount of W powder is used. Since it is necessary to contain or reduce the average particle size of the W powder, the optimum average particle size of the WC powder was selected from the average particle size and the content of the W powder.
The average particle size of each raw material powder was measured by using the BET method for nano-level powder and using the laser diffraction method for μm-level powder.
焼結体
得られた原料混合粉末を油圧プレス等にて成形圧１ＭＰａにて、プレス成形し、成形体を製造した。次いで、圧力５０ＭＰａ～１０ＧＰａ、温度１５５０～２３００℃、保持時間５～１２０分間の条件にて、高温高圧焼結を行った。
Sintered body The obtained raw material mixed powder was press-molded with a hydraulic press or the like at a molding pressure of 1 MPa to produce a molded body. Next, high-temperature and high-pressure sintering was performed under the conditions of a pressure of 50 MPa to 10 GPa, a temperature of 1550 to 2300 ° C., and a holding time of 5 to 120 minutes.
＜表面被膜の形成＞
本発明に係る焼結体から研削加工により切削工具を作製し、その表面にＣＶＤ法によりＴｉＣＮおよびＡｌ２Ｏ３層を被覆しコーティング工具を作製した。刃先が高温となる高速度・高切込みの切削条件においても飛躍的な長寿命を示し、刃先が高温になりやすい切削用工具としてすぐれていることが示された。また、この焼結体は、耐食性にもすぐれており、シールリングなどの用途にも使用できる。また、ガラスレンズの成形用金型としても有用である。
<Formation of surface coating>
A cutting tool was produced from the sintered body according to the present invention by grinding , and the surface thereof was coated with TiCN and Al2O3 layers by a CVD method to produce a coating tool. It showed a dramatically long life even under high speed and high cutting conditions where the cutting edge becomes hot, and it was shown that it is excellent as a cutting tool where the cutting edge tends to get hot. In addition, this sintered body has excellent corrosion resistance and can be used for applications such as sealing rings. It is also useful as a mold for molding a glass lens.
本発明は、高硬度、高強度かつ高融点セラミックとして知られるＷＣ粒子からなる硬質相と、前記ＷＣと親和性にすぐれたＷ２Ｃ粒子とＷＯ２ 粒子とからなり、焼結体組織中にＷ２Ｃ粒子とＷＯ２ 粒子が微粒分散してなる焼結体であって、原料粉末の微細化と適正範囲への粒度調整、及び、グラフェンの混合と、表面への酸素付与量の調整を行い、さらに、焼結条件、特に焼結温度を調整することにより、Ｗ２Ｃ粒子とＷＯ２ 粒子を組織中に分散析出させることにより、高硬度、高強度、緻密性、耐食性、および、破壊靱性特性にすぐれた有用な焼結体を提供するものである。 The present invention comprises a hard phase composed of WC particles known as high hardness, high strength and high melting point ceramic, and W2C particles and WO2 particles having excellent affinity with the WC. It is a sintered body in which W 2 C particles and WO 2 particles are finely dispersed, and it is possible to make the raw material powder finer, adjust the particle size to an appropriate range, mix graphene, and adjust the amount of oxygen applied to the surface. By further adjusting the sintering conditions, especially the sintering temperature, W2C particles and WO2 particles are dispersed and precipitated in the structure, thereby resulting in high hardness, high strength, compactness, corrosion resistance, and fracture. It provides a useful sintered body having excellent toughness properties.
つぎに、本発明の焼結体について、実施例により具体的に説明する。 Next, the sintered body of the present invention will be specifically described with reference to Examples.
原料粉末として、所定の平均粒径を有するＷＣ粉末と、表面へ酸素付与したＷ粉末と、所定の形状、厚みを有するグラフェンとを用意し、表３に示すように、これらの原料粉末を所定組成に配合し混合熱処理した後、焼結を行うことによって、本発明焼結体１～３を製造した。 As raw material powders, WC powder having a predetermined average particle size, W powder obtained by applying oxygen to the surface, and graphene having a predetermined shape and thickness are prepared, and as shown in Table 3, these raw material powders are specified. The sintered bodies 1 to 3 of the present invention were produced by blending them into the composition, mixing and heat-treating them, and then sintering them.
また、比較の目的で、原料粉としてグラフェンを含まないこと以外は、表３に示される本発明焼結体１～３と同様の製造条件（表３の試料番号１１、１２）にて、比較例焼結体１１および１２を製造した。 Further, for the purpose of comparison, comparison was made under the same production conditions as the sintered bodies 1 to 3 of the present invention shown in Table 3 (sample numbers 11 and 12 in Table 3) except that graphene was not contained as the raw material powder. Examples Sintered bodies 11 and 12 were manufactured.
上記で得られた本発明焼結体１～３、比較例焼結体１１、１２について、それぞれの断面組織をＳＥＭ－ＥＤＸ（倍率：１００００倍）およびＥＢＳＤ（倍率：１００００倍）で観察するとともに、画像処理により測定された、焼結体を構成するＷＣ、Ｗ２Ｃ、ＷＯ２の各粒の体積量、平均粒径およびＷＯ２ 粒子の単位面積当たりの平均個数（平均密度）を表４に示す。 With respect to the sintered bodies 1 to 3 of the present invention and the sintered bodies 11 and 12 of Comparative Examples obtained above, the cross-sectional structures of each were observed with SEM-EDX (magnification: 10000 times) and EBSD (magnification: 10000 times). Table 4 shows the volume volume, average particle size , and average number of WO 2 particles per unit area (average density) of each of the WC, W 2 C, and WO 2 grains constituting the sintered body, which were measured by image processing. Shown in.
また、同様に、本発明焼結体１～３、比較例焼結体１１、１２について、密度値についても測定を行い、表４に示す。 Similarly, the density values of the sintered bodies 1 to 3 of the present invention and the sintered bodies 11 and 12 of the comparative examples were also measured and are shown in Table 4.
図２および図３には、本発明焼結体１および本発明焼結体２のＸＲＤチャート図を示す。
図２および図３より明らかなとおり、少なくともＷ２Ｃ、ＷＣ、ＷＯ２以外のピークを確認することはできなかった。
2 and 3 show XRD charts of the sintered body 1 of the present invention and the sintered body 2 of the present invention.
As is clear from FIGS. 2 and 3, at least peaks other than W2C , WC, and WO2 could not be confirmed.
表４より明らかなとおり、本発明焼結体１～３は、焼結体を構成するＷ２Ｃ粒子およびＷＯ２
粒子の平均粒径はいずれも上限の１５０ｎｍを大きく下回っており、微細組織構造を有するものであり、体積量についても、Ｗ２Ｃ粒子は５０体積％以下、ＷＯ２
粒子は５．０体積％以下であるため、硬質相であるＷＣ粒子に対し、結合相の役割を果たし、十分な硬度、強度に加え、すぐれた緻密性や破壊靱性特性を有することが期待される。
これに対し、比較焼結体１１、１２では、少なくとも焼結体を構成するＷ２Ｃ粒子において、その平均粒径は５００ｎｍ近くであって、硬質相であるＷＣ粒子の平均粒径とほぼ同等であり、しかも、その体積量もＷＣ粒子の体積量を上回り、５０体積％を超えていることから、特に、緻密性や破壊靱性特性に劣ることが想定される。
As is clear from Table 4, in the sintered bodies 1 to 3 of the present invention, the average volumetric particles of the W2C particles and WO2 particles constituting the sintered body are both well below the upper limit of 150 nm, and have a microstructure structure. In terms of volume, W 2 C particles have a volume of 50% by volume or less , and WO 2 particles have a volume of 5.0% by volume or less. In addition to sufficient hardness and strength, it is expected to have excellent compactness and fracture toughness properties.
On the other hand, in the comparative sintered bodies 11 and 12, at least the W2C particles constituting the sintered body have an average particle size of about 500 nm, which is almost the same as the average particle size of the WC particles which are the hard phase. Moreover, since the volume of the WC particles exceeds the volume of the WC particles and exceeds 50% by volume, it is assumed that the compactness and the fracture toughness characteristics are particularly inferior.
そこで、本発明焼結体１～３及び比較例焼結体１１、１２を用い研削加工により切削工具を作製し、その表面にＣＶＤ法によりＴｉＣＮ及びＡｌ２Ｏ３層を被覆し、本発明焼結体工具１～３及び比較例焼結体工具１１、１２を作製し、以下に示す切削条件にて高速高送り切削加工試験を実施した。
被削材 ：Ｓ４５Ｃ
切削速度：２００ｍ／分
切り込み：１．０ｍｍ
送り ：０．７ｍｍ
最大切削時間１２０秒まで切削加工試験を実施し、切削時間１５秒毎に刃先を確認した。表４に試験結果を示す。
表４に示される結果から、本発明焼結体工具１～３は、高速度・高切り込みの過酷な切削条件においても長寿命を示し、切込み刃先が高温になりやすい切削用工具として特にすぐれていることが示された。
他方、比較例焼結体工具１１、１２は、いずれも工具寿命が短く、しかも、刃先は欠損を生じていた。
Therefore, a cutting tool is produced by grinding using the sintered bodies 1 to 3 of the present invention and the sintered bodies 11 and 12 of the comparative examples, and the surface thereof is coated with the TiCN and Al2O3 layers by the CVD method, and the firing of the present invention is performed. Bound tools 1 to 3 and comparative examples sintered tools 11 and 12 were manufactured, and a high-speed high-feed cutting process test was carried out under the cutting conditions shown below.
Work material: S45C
Cutting speed: 200m / min
Notch: 1.0 mm
Feed: 0.7 mm
A cutting test was carried out up to a maximum cutting time of 120 seconds, and the cutting edge was confirmed every 15 seconds of cutting time. Table 4 shows the test results.
From the results shown in Table 4, the sintered body tools 1 to 3 of the present invention show a long life even under severe cutting conditions of high speed and high cutting, and are particularly excellent as cutting tools in which the cutting edge tends to have a high temperature. It was shown to be.
On the other hand, the sintered body tools 11 and 12 of the comparative examples all had a short tool life, and the cutting edge was defective.
本発明に係る焼結体は、高強度、高硬度であり、切削工具として用いた場合に長寿命を示すことから、切削工具の刃先材料あるいは高温で使用される金型などの耐摩耗性工具材料として用いることができ、きわめて有用である。 Since the sintered body according to the present invention has high strength and high hardness and exhibits a long life when used as a cutting tool, it is a wear-resistant tool such as a cutting tool material or a mold used at a high temperature. It can be used as a material and is extremely useful.
Claims (2)
前記Ｗ２Ｃ粒子と前記酸化タングステン（ＷＯ２）粒子は、平均粒径が５ｎｍ以上１５０ｎｍ以下であり、焼結体組織内において、前記酸化タングステン（ＷＯ２ ）粒子が５５個／μｍ ２ ～４０個／μｍ２の平均密度にて存在することを特徴とする焼結体。 The hard phase contains 50 vol% to 95 vol% of tungsten carbide (WC) particles , the bound phase contains 4 vol% to 50 vol% of W 2 C particles , and 0.5 vol% to 5.0 vol% of tungsten oxide (WO 2 ). It is a sintered body containing
The W 2 C particles and the tungsten oxide (WO 2 ) particles have an average particle size of 5 nm or more and 150 nm or less, and the tungsten oxide ( WO 2 ) particles are 55 particles / μm 2 or more in the sintered body structure. A sintered body characterized by being present at an average density of 40 particles / μm 2 .
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| US20120261643A1 (en) | 2011-04-18 | 2012-10-18 | International Business Machines Corporation | GRAPHENE NANORIBBONS AND CARBON NANOTUBES FABRICATED FROM SiC FINS OR NANOWIRE TEMPLATES |
| JP2018150194A (en) | 2017-03-13 | 2018-09-27 | 三菱マテリアル株式会社 | Hard sintered body |
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| JP2004142993A (en) | 2002-10-24 | 2004-05-20 | Toshiba Tungaloy Co Ltd | Hexagonal composite carbide, and production method therefor |
| JP4713119B2 (en) | 2003-09-24 | 2011-06-29 | サンドビック インテレクチュアル プロパティー アクティエボラーグ | Cutting tool insert and manufacturing method thereof |
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