JP4601304B2 - Alumina / zirconia ceramics and process for producing the same - Google Patents
Alumina / zirconia ceramics and process for producing the same Download PDFInfo
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Description
本発明は、アルミナ・ジルコニア系セラミックスに関するものであって、特に種々の構造部材、切削工具、医療用器具、生体用材料に好適に使用されるアルミナ・ジルコニア系セラミックスおよびその製法に関する。 The present invention relates to alumina / zirconia ceramics, and particularly to alumina / zirconia ceramics suitably used for various structural members, cutting tools, medical instruments, and biomaterials, and a method for producing the same.
近年、アルミナ、ジルコニア系の酸化物セラミックスは、高強度、耐摩耗性及び耐食性が要求される構造部材として広く利用されている。特に、アルミナとジルコニアを一定の比率で含むアルミナ・ジルコニア系セラミックスは、結晶粒の微細化効果により、それぞれの単体セラミックスよりも高い強度が得られることが注目されている（非特許文献１参照）。 In recent years, alumina and zirconia-based oxide ceramics have been widely used as structural members that require high strength, wear resistance, and corrosion resistance. In particular, alumina / zirconia ceramics containing alumina and zirconia at a certain ratio are attracting attention because of the effect of refining crystal grains, higher strength than the individual ceramics can be obtained (see Non-Patent Document 1). .
しかし、上記のアルミナ・ジルコニア系セラミックスは、切削工具として用いた場合、靭性不足が原因で切刃に欠損やチッピングが生じ易く、実用に供する事ができないという欠点がある。このため、形状異方性粒子を生成させることによる靭性改善等が行なわれている。例えば、ＳｒＯ、ＣａＯ、或いはＢａＯとＳｉＯ２とを焼成時に共存させることにより、高靭性アルミナ−ジルコニア複合材料が得られることが知られている（例えば、特許文献１参照）。即ち、ＣａＯ等を、アルミナ及びジルコニアの焼成時に共存させることにより、Ａｌ２Ｏ３結晶が細長く成長し、Ａｌ２Ｏ３粒子が細長成長結晶からなる組織を持つようになり、この細長成長Ａｌ２Ｏ３結晶によって優れた靭性を具備するようになるのである。 However, when the above-mentioned alumina / zirconia ceramics are used as a cutting tool, there is a drawback that the cutting edge is easily damaged or chipped due to insufficient toughness and cannot be put to practical use. For this reason, the toughness improvement etc. are performed by producing | generating a shape anisotropic particle. For example, it is known that a high toughness alumina-zirconia composite material can be obtained by allowing SrO, CaO, or BaO and SiO 2 to coexist during firing (see, for example, Patent Document 1). That is, by making CaO or the like coexist at the time of firing alumina and zirconia, the Al 2 O 3 crystal grows elongated and the Al 2 O 3 particles have a structure composed of the elongated growth crystal, and this elongated growth Al 2 The O 3 crystal has excellent toughness.
ところが、形状異方性粒子の生成によって破壊靭性が向上する一方で、強度と硬度が低下することが知られている。破壊靭性をより高くする為には形状異方性粒子をより細長く成長させる必要があるが、粒子が大きくなるほど強度と硬度が低下してしまう。即ち、前記特許文献１に開示されているようなアルミナ・ジルコニア系セラミックスでは、アルミナの異方性成長により靭性改善効果が見られるものの、曲げ強度が例えば１０５０ＭＰａ以下となり、形状異方性粒子の生成によって強度が低下してしまう。 However, it is known that the generation of shape anisotropic particles improves the fracture toughness while decreasing the strength and hardness. In order to further increase the fracture toughness, it is necessary to grow the shape anisotropic particles longer and longer, but the strength and the hardness decrease as the particles become larger. That is, in the alumina / zirconia ceramics disclosed in Patent Document 1, although the toughness improving effect is observed by the anisotropic growth of alumina, the bending strength becomes, for example, 1050 MPa or less, and the formation of shape anisotropic particles As a result, the strength decreases.
従って、本発明の目的は、粒成長を抑えながら、靭性が向上しており、高強度で且つ高靭性のアルミナ・ジルコニア系セラミックスを提供することにある。 Accordingly, an object of the present invention is to provide an alumina / zirconia ceramic having high toughness and high toughness while suppressing grain growth.
本発明者らは、アルミナ主体のアルミナ・ジルコニア系セラミックスにおいて、所定量のＣａＯを配合して焼成を行い、形状異方性粒子の生成を抑えつつ、一部のＺｒＯ２粒子にＣａＯを固溶させることにより、正方晶ＺｒＯ２の準安定化を実現し、単斜晶への応力誘起相転移によって強度と破壊靭性とを向上できること、更に焼結助剤としてＴｉＯ２、ＭｇＯ及びＳｉＯ２を所定量使用することにより、ＺｒＯ２へのＣａＯの固溶が促進され、応力誘起相転移強化の効果が大きくできることを見出し、本発明に至った。 In the alumina-zirconia-based ceramics mainly composed of alumina, the inventors of the present invention compounded and fired a predetermined amount of CaO to suppress the formation of shape anisotropic particles, while dissolving CaO in some ZrO 2 particles. Therefore, the metastabilization of tetragonal ZrO 2 can be realized, and the strength and fracture toughness can be improved by the stress-induced phase transition to monoclinic crystal. Further, TiO 2 , MgO and SiO 2 can be used as sintering aids. It has been found that by using quantitatively, the solid solution of CaO in ZrO 2 is promoted and the effect of strengthening the stress-induced phase transition can be increased, and the present invention has been achieved.
すなわち、本発明によれば、Ａｌ２Ｏ３粒子及びＺｒＯ２粒子を含有するアルミナ・ジルコニア系セラミックスにおいて、
Ａｌ２Ｏ３含量が７２．１〜８０質量％であり、ＺｒＯ２含量が１８〜２５質量％の範囲にあり、前記ＺｒＯ２粒子の一部には、ＣａＯが固溶しており、且つ、ＣａＯ含量が０．１〜４質量％の範囲にあるとともに、さらに、ＴｉＯ２、ＭｇＯ及びＳｉＯ２を含有しており、ＳｉＯ ２ 含量が０．４〜１．５質量％、ＴｉＯ ２ 含量が０．３〜０．７質量％、ＭｇＯ含量が０．２〜１．４質量％であり、且つＳｉＯ ２ 、ＴｉＯ ２ 及びＭｇＯの合計含量が０．６〜３．６質量％の範囲にあることを特徴とするアルミナ・ジルコニア系セラミックスが提供される。
That is, according to the present invention, in the alumina / zirconia-based ceramics containing Al 2 O 3 particles and ZrO 2 particles,
Al 2 O 3 content is 72.1 to 80 wt%, the range ZrO 2 content of 18-25 wt%, a part of the ZrO 2 particles, CaO has a solid solution, and, The CaO content is in the range of 0.1 to 4% by mass, and further contains TiO 2 , MgO and SiO 2. The SiO 2 content is 0.4 to 1.5% by mass and the TiO 2 content is 0. .3～0.7 wt%, MgO content is 0.2 to 1.4 wt%, and the total content of SiO 2, TiO 2 or MgO is in the range of 0.6 to 3.6 mass% Alumina / zirconia ceramics are provided.
さらに、本発明によれば、
Ａｌを酸化物換算で７２．１〜８０質量％、Ｚｒを酸化物換算で１８〜２５質量％及びＣａを酸化物換算で０．１〜４質量％の量で含有し、さらにＳｉを酸化物換算で０．４〜１．５質量％、Ｔｉを酸化物換算で０．３〜０．７質量％、Ｍｇを酸化物換算で０．２〜１．４質量％の量で含有し、且つＳｉ、Ｔｉ及びＭｇの酸化物換算での合計含量が０．６〜３．６質量％の範囲にある原料粉末を用意し、
前記原料粉末を所定形状に成形し、
得られた成形体を、１３００℃〜１５００℃の温度範囲で焼成し、
更に前記焼成温度より３０℃以上低い温度で熱間静水圧処理すること、
を特徴とするアルミナ・ジルコニア系セラミックスの製法が提供される。
Furthermore, according to the present invention,
Al is contained in an amount of 72.1 to 80 % by mass in terms of oxide , Zr is contained in an amount of 18 to 25 % by mass in terms of oxide, Ca is contained in an amount of 0.1 to 4% by mass in terms of oxide, and Si is an oxide. 0.4 to 1.5 mass % in terms of conversion , Ti in an amount of 0.3 to 0.7 mass % in terms of oxide , Mg in an amount of 0.2 to 1.4 mass % in terms of oxide, and A raw material powder having a total content in terms of oxides of Si, Ti and Mg in the range of 0.6 to 3.6 % by mass is prepared,
The raw material powder is molded into a predetermined shape,
The obtained molded body was fired at a temperature range of 1300 ° C to 1500 ° C,
Furthermore, hot isostatic pressing at a temperature lower by 30 ° C. or more than the firing temperature,
A method for producing an alumina / zirconia ceramics is provided.
本発明のアルミナ・ジルコニアセラミックスでは、特にＺｒＯ２粒子の一部にＣａＯが固溶していることにより、ＣａＯによる正方晶ＺｒＯ２の安定化効果が発現し、応力誘起相転移の効果によって高強度化、高靭性化が達成されており、例えば１２７０ＭＰａ以上の曲げ強度、４．８ＭＰａ・ｍ１／２以上の破壊靭性、及び１７４０以上のビッカース硬度を有している。 In the alumina / zirconia ceramic of the present invention, CaO is dissolved in a part of the ZrO 2 particles, so that the effect of stabilizing the tetragonal ZrO 2 by CaO is manifested, and the high strength is obtained by the effect of the stress-induced phase transition. For example, it has a bending strength of 1270 MPa or more, a fracture toughness of 4.8 MPa · m 1/2 or more, and a Vickers hardness of 1740 or more.
また、本発明の製法では、焼結助剤として機能するＳｉＯ２、ＴｉＯ２及びＭｇＯが一定の量割合で存在する条件下で焼成が行われる結果、ＣａＯとＡｌ２Ｏ３との反応が抑制され、ＣａＯのＺｒＯ２への固溶が促進され、且つ形状異方性粒子の生成が有効に抑制され、且つ高緻密化、組織微細化が達成され、その結果、上述した高強度、高靭性、さらには高硬度のアルミナ・ジルコニア系セラミックスを得ることが可能となる。 Further, in the method of the present invention, the reaction of SiO 2, a result of TiO 2 and MgO are calcined under the conditions present in certain proportions is performed, CaO and Al 2 O 3 which acts as a sintering aid is suppressed Thus, solid solution of CaO in ZrO 2 is promoted, formation of shape anisotropic particles is effectively suppressed, and high densification and microstructure refinement are achieved. As a result, the above-described high strength and high toughness are achieved. In addition, it is possible to obtain an alumina / zirconia ceramic with high hardness.
（アルミナ・ジルコニアセラミックス）
本発明のセラミックスは、基本成分として、Ａｌ２Ｏ３粒子及びＺｒＯ２粒子を含有するものであるが、アルミナリッチの組成を有しており、Ａｌ２Ｏ３を７２．１〜８０質量％の量で含有し、ＺｒＯ２を１８〜２５質量％の量で含有している。即ち、Ａｌ２Ｏ３を７２．１〜８０質量％含有させることにより、高強度でかつ高硬度という効果を達成することが可能となり、ＺｒＯ２の含有量が１８質量％未満では強度が低下し、低靭性となり、一方、２５質量％を超えるとヤング率低下により硬度が低下してしまう。
(Alumina / zirconia ceramics)
The ceramic of the present invention contains Al 2 O 3 particles and ZrO 2 particles as basic components, but has an alumina-rich composition and contains 72.1 to 80 % by mass of Al 2 O 3. It is contained in an amount, and ZrO 2 is contained in an amount of 18 to 25 % by mass. That is, by Al the 2 O 3 72.1-80 wt% containing organic, it is possible to achieve the effect of high strength and high hardness, decreased strength in the content of ZrO 2 is less than 18 wt% On the other hand, if it exceeds 25 % by mass, the hardness decreases due to a decrease in Young's modulus.
また、本発明のセラミックスは、ＣａＯを０．１〜４質量％、好ましくは０．５〜３質量％、特に好ましくは０．７〜１．５質量％の量で含有している。ＣａＯ含量が上記範囲よりも少量であると、ＺｒＯ２の単斜晶系が多くなり、強度が低下する。またＣａＯ含量が上記範囲よりも多いものは、焼成温度を高くしなければ得ることができず、このため、形状異方性粒子による緻密化阻害や、ジルコニア粒成長による強度あるいは硬度の低下がおきる。 The ceramic of the present invention contains CaO in an amount of 0.1 to 4% by mass, preferably 0.5 to 3% by mass, particularly preferably 0.7 to 1.5% by mass. When the CaO content is less than the above range, the monoclinic system of ZrO 2 increases and the strength decreases. In addition, when the CaO content is higher than the above range, it cannot be obtained unless the firing temperature is increased. For this reason, densification is inhibited by shape anisotropic particles, and strength or hardness is reduced by zirconia grain growth. .
さらに、本発明のセラミックスでは、上記のＣａＯ成分の存在に関連して、ＺｒＯ２粒子の一部にＣａＯが固溶していることが重要であり、これにより、破壊靭性を向上でき、同時に高強度化、高硬度化を実現できる。 Further, in the ceramic of the present invention, it is important that CaO is dissolved in a part of the ZrO 2 particles in relation to the presence of the above CaO component. Strengthening and high hardness can be realized.
通常ＺｒＯ２は、Ｙ２Ｏ３などの安定化剤を適量固溶させることで機械的特性を向上させることができる。しかし、アルミナ・ジルコニア系セラミックスでは、Ｙ２Ｏ３の配合量が多すぎると立方晶が多くなり相変態の破壊靭性への寄与が小さくなる。一方、Ｙ２Ｏ３の配合量が少なすぎると単斜晶ＺｒＯ２が多くなり、強度、靭性ともに低下する。このように、Ｙ２Ｏ３などによって安定化されたＺｒＯ２粒子を存在させたのでは、破壊靭性、強度及び硬度を同時に向上させることができない。 Usually, ZrO 2 can improve mechanical properties by dissolving a proper amount of a stabilizer such as Y 2 O 3 . However, in alumina / zirconia ceramics, if the amount of Y 2 O 3 is too large, the number of cubic crystals increases and the contribution to the fracture toughness of the phase transformation decreases. On the other hand, if the blending amount of Y 2 O 3 is too small, monoclinic ZrO 2 increases, and both strength and toughness decrease. Thus, the presence of ZrO 2 particles stabilized by Y 2 O 3 or the like cannot improve the fracture toughness, strength and hardness at the same time.
しかるに、本発明では、ＣａＯの固溶により正方晶ＺｒＯ２の安定化が実現し、この結果、応力誘起相転移効果が大きく、形状異方性粒子生成によらず破壊靭性を向上でき、従って、形状異方性粒子生成による強度や硬度の低下を回避することができ、破壊靭性、強度及び硬度を同時に向上させることができるわけである。 However, in the present invention, the stabilization of tetragonal ZrO 2 is realized by the solid solution of CaO. As a result, the stress-induced phase transition effect is large, and the fracture toughness can be improved regardless of the formation of shape anisotropic particles. The decrease in strength and hardness due to the formation of shape anisotropic particles can be avoided, and the fracture toughness, strength and hardness can be improved at the same time.
本発明のアルミナ・ジルコニアセラミックスでは、上述した各成分に加えて、ＳｉＯ２、ＴｉＯ２及びＭｇＯを含有する。即ち、これらの酸化物成分は、焼結助剤に由来するものであり、このような成分を含有していることにより、ＣａＯのＺｒＯ２粒子への固溶が促進され、さらにはＡｌ２Ｏ３及びＺｒＯ２の結晶粒成長を抑制しながら、低い温度条件で焼結体を緻密化でき、微粒、高密度の組織形成により高強度化の実現に有利となる。 The alumina / zirconia ceramic of the present invention contains SiO 2 , TiO 2, and MgO in addition to the components described above. That is, these oxide components are derived from the sintering aid, and by containing such components, the solid solution of CaO in the ZrO 2 particles is promoted, and further Al 2 O While suppressing the growth of crystal grains of 3 and ZrO 2, the sintered body can be densified under low temperature conditions, and formation of fine grains and high density structure is advantageous for realizing high strength.
ＣａＯが固溶したＺｒＯ２は、正方晶の領域が広く、立方結晶が生成しにくいため、安定化剤として好適である。しかるに、Ａｌ２Ｏ３が主成分であるアルミナ・ジルコニア系セラミックスでは、ＣａＯがＡｌ２Ｏ３と優先的に反応してしまい、形状異方性粒子が生成し、破壊靭性の向上は実現できるが、強度及び硬度の低下を生じてしまう。しかるに、本発明では、上記のような焼結助剤成分の使用により、ＣａＯとＡｌ２Ｏ３との反応が抑制され、形状方性粒子の生成が抑制されると同時に、ＣａＯのＺｒＯ２粒子への固溶が促進されることとなる。この結果、ＣａＯの固溶による正方晶ＺｒＯ２の安定化が実現し、応力誘起相転移の強化効果が大きく、強度や硬度を低下させず、破壊靭性を高めることができるのである。 ZrO 2 in which CaO is a solid solution has a wide tetragonal region and is difficult to form cubic crystals, and thus is suitable as a stabilizer. However, in the alumina / zirconia-based ceramics mainly composed of Al 2 O 3 , CaO reacts preferentially with Al 2 O 3 to generate shape anisotropic particles, which can improve fracture toughness. This will cause a decrease in strength and hardness. However, in the present invention, the use of the sintering aid component as described above suppresses the reaction between CaO and Al 2 O 3 and suppresses the formation of shape isotropic particles, and at the same time, the ZrO 2 particles of CaO. The solid solution is promoted. As a result, the stabilization of tetragonal ZrO 2 by the solid solution of CaO is realized, the effect of strengthening the stress-induced phase transition is great, and the fracture toughness can be increased without reducing the strength and hardness.
本発明において、ＳｉＯ２の含有量は、０．４〜１．５質量％の範囲にあり、ＴｉＯ２の含有量は、０．３〜０．７質量％の範囲にあり、さらにＭｇＯの含有量は、０．２〜１．４質量％の範囲にある。各酸化物成分の含有量が、上記範囲よりも少ないと、焼成時に液相が不足し、焼成温度を高くしなければならず、高温焼成によってＣａＯとＡｌ２Ｏ３との反応が促進されてしまい、ＣａＯが固溶したＺｒＯ２が得られにくくなってしまう。 In the present invention, the content of SiO 2 is 0 . Range near the 4 to 1.5 mass% is, the content of TiO 2 is 0. Range near the 3 to 0.7 wt% is, further the content of MgO is 0. Area by the near of 2 to 1.4% by weight. When the content of each oxide component is less than the above range, the liquid phase is insufficient at the time of firing, the firing temperature must be increased, and the reaction between CaO and Al 2 O 3 is promoted by the high temperature firing. Therefore, it becomes difficult to obtain ZrO 2 in which CaO is dissolved.
また、上記のＳｉＯ２、ＴｉＯ２及びＭｇＯの含有量は、合計で０．６〜３．６質量％の範囲とすることが好ましい。即ち、焼結助剤に由来するこれら成分が、このような範囲で存在していると、ＣａＯのＺｒＯ２への固溶が促進され、強度、靭性が向上すると共に、共晶点が１３００℃以下になり、焼結時に液相が生成して焼結が大きく促進される。この為、より低い温度での焼成により、高い緻密性の焼結体が得られ、比較的低温での焼結は、異方粒成長を抑制し、微細な組織のとなり、強度や硬度の低下を回避するのに有利となる。 Further, SiO 2, TiO 2 and MgO content above is preferably in a range of 0.6 to 3.6 mass% in total. That is, when these components derived from the sintering aid are present in such a range, solid solution of CaO in ZrO 2 is promoted, strength and toughness are improved, and the eutectic point is 1300 ° C. As a result, a liquid phase is generated during sintering and sintering is greatly promoted. For this reason, a sintered body having a high density can be obtained by firing at a lower temperature. Sintering at a relatively low temperature suppresses anisotropic grain growth, becomes a fine structure, and decreases strength and hardness. It is advantageous to avoid.
上記のような組成を有する本発明のアルミナ・ジルコニアセラミックスは、後述する実施例から明らかな通り、１１５０ＭＰａ以上の曲げ強度、４．６ＭＰａ・ｍ１／２以上の破壊靭性、及び１７４０以上のビッカース硬度を有しており、種々の構造部材、切削工具、医療用器具などの用途に適している。 The alumina / zirconia ceramics of the present invention having the above composition has a bending strength of 1150 MPa or more, a fracture toughness of 4.6 MPa · m 1/2 or more, and a Vickers hardness of 1740 or more, as will be apparent from Examples described later. It is suitable for various structural members, cutting tools, medical instruments and the like.
（アルミナ・ジルコニア系セラミックスの製法）
上述した本発明のアルミナ・ジルコニアセラミックスは、所定の組成の原料粉末を調製し、所定形状に成形し、焼成及び熱間静水圧処理することにより製造される。
(Alumina / zirconia ceramics manufacturing method)
The above-described alumina / zirconia ceramic of the present invention is produced by preparing a raw material powder having a predetermined composition, forming it into a predetermined shape, firing and hot isostatic pressing.
用いる原料粉末は、前述した組成の焼結体が得られるように、各種の金属分を含んでおり、例えばＡｌ２Ｏ３源となるＡｌ分、ＺｒＯ２源となるＺｒ分、及びＣａＯ源となるＣａ分を含み、且つ焼結助剤としてのＳｉ分、Ｔｉ分及びＭｇ分を含有する。これら金属分は、一般的には酸化物の形で使用されるが、焼成により、前述した各種の酸化物を形成するものであれば酸化物に限定されるものではなく、金属単体、水酸化物、あるいは炭酸塩などの塩類の形で使用することもできる。即ち、原料粉末は、これらの金属分の粉末を混合することにより調製され、原料粉末中の各種金属分の含有割合は、Ａｌ、Ｚｒ、Ｃａ、Ｓｉ、Ｔｉ及びＭｇ量が、酸化物換算で、前述した焼結体の組成に対応するように設定される。また、原料粉末の平均粒径は、一般に、１．０μｍ以下が好ましい。 The raw material powder used includes various metal components so that a sintered body having the above-described composition can be obtained. For example, an Al component serving as an Al 2 O 3 source, a Zr component serving as a ZrO 2 source, and a CaO source And a Si component, a Ti component, and a Mg component as a sintering aid. These metal components are generally used in the form of oxides, but are not limited to oxides as long as they form the above-mentioned various oxides by firing. Or in the form of a salt such as carbonate. That is, the raw material powder is prepared by mixing these metal powders, and the content of various metals in the raw material powder is such that the amounts of Al, Zr, Ca, Si, Ti and Mg are in terms of oxides. , Is set to correspond to the composition of the sintered body described above. The average particle size of the raw material powder is generally preferably 1.0 μm or less.
原料粉末を用いての成形は、必要により、水や有機溶媒等の溶媒、有機バインダーなどを用いて原料粉末のスラリー乃至ペーストもしくはこれらを乾燥して得られる粉末を調製し、このようなスラリー乃至ペーストもしくは粉末を用いて行うことも可能である。また、成形手段としては、プレス成形、鋳込み、冷間静水圧成形、或いは冷間静水圧処理など、それ自体公知の手段を採用することができる。 The molding using the raw material powder is carried out by preparing a slurry or paste of the raw material powder or a powder obtained by drying these using a solvent such as water or an organic solvent, an organic binder, etc. It is also possible to use a paste or powder. Further, as the forming means, means known per se such as press molding, casting, cold isostatic pressing, or cold isostatic treatment can be employed.
上記成形体の焼成は、１３００〜１５００℃、特に１３００乃至１４９０℃の温度範囲で行われ、これにより、Ａｌ２Ｏ３やＺｒＯ２の粒成長を抑制しながら緻密化することができる。例えば、ＣａＯが存在する条件下で１５００℃よりも高い温度で焼成を行うと、ＣａＯとＡｌ２Ｏ３が反応して異方粒成長し、焼結体の強度や硬度が低下してしまう。また、ＺｒＯ２の粒成長によって単斜晶ＺｒＯ２量が増加することによっても、強度や硬度の低下がもたらされる。また、１３００℃よりも低温での焼成では、緻密化が困難となってしまう。 The molded body is fired at a temperature in the range of 1300 to 1500 ° C., particularly 1300 to 1490 ° C., thereby enabling densification while suppressing grain growth of Al 2 O 3 and ZrO 2 . For example, if firing is performed at a temperature higher than 1500 ° C. in the presence of CaO, CaO and Al 2 O 3 react to grow anisotropically, resulting in a decrease in strength and hardness of the sintered body. Further, also by monoclinic ZrO 2 amount by grain growth of ZrO 2 is increased, decrease in strength and hardness is provided. Further, densification becomes difficult by firing at a temperature lower than 1300 ° C.
本発明においては、焼結助剤として、所定量のＳｉＯ２、ＴｉＯ２及びＭｇＯが使用されているため、ＣａＯとＡｌ２Ｏ３との反応が抑制され、ＣａＯのＺｒＯ２への固溶が促進されると共に、共晶点が１３００℃以下になり、焼結時に液相が生成して材料の焼結が大きく促進される。この為、上記のような比較的低温領域での焼成により、緻密性の高い焼結体を得ることができる。また、このような比較的低温領域で焼結することによって、異方粒成長が抑制され、微細な組織となり、強度や硬度を低下させず、靭性を高めることができるのである。 In the present invention, since predetermined amounts of SiO 2 , TiO 2, and MgO are used as sintering aids, the reaction between CaO and Al 2 O 3 is suppressed, and the solid solution of CaO in ZrO 2 is prevented. In addition to being promoted, the eutectic point becomes 1300 ° C. or lower, and a liquid phase is generated during sintering, so that the sintering of the material is greatly promoted. For this reason, a sintered compact with high density can be obtained by firing in a relatively low temperature region as described above. Further, by sintering in such a relatively low temperature region, anisotropic grain growth is suppressed, a fine structure is obtained, and the toughness can be increased without lowering the strength and hardness.
上記のような温度範囲での焼成時間は、例えばアルキメデス法による相対密度が９５％以上となる程度でよく、通常、１乃至５時間程度である。 The baking time in the above temperature range may be such that the relative density by the Archimedes method is 95% or more, and is usually about 1 to 5 hours.
上記の焼成に引き続いて行われる熱間静水圧処理は、前記焼成温度より３０℃以上低い温度、好ましくは５０℃以上低い温度、更に好ましくは１００℃以上低い温度で行われ、これによりアルミナ、ジルコニアが微粒で、アルミナの異方粒成長を抑えた緻密なアルミナ・ジルコニア系セラミックスを作製することができ、この焼結体は、既に述べたように、靭性が高く、しかも高強度、高硬度という特性を有している。 The hot isostatic pressure treatment performed following the firing is performed at a temperature that is 30 ° C. or more lower than the firing temperature, preferably 50 ° C. or more, and more preferably 100 ° C. or more, whereby alumina or zirconia. Can be used to produce dense alumina / zirconia ceramics that suppress the growth of anisotropic grains of alumina. As already mentioned, this sintered body has high toughness, high strength, and high hardness. It has characteristics.
尚、上記の熱間静水圧処理は、短時間でアルミナやジルコニアを微粒化させるため、通常、その下限温度は、１２００℃以上、特に１２５０℃以上とするのがよく、一般に、０．５乃至２時間程度行えばよい。 The hot isostatic pressure treatment atomizes alumina or zirconia in a short time, and therefore the lower limit temperature is usually 1200 ° C. or higher, particularly 1250 ° C. or higher. It may be performed for about 2 hours.
純度が９９．９５質量％で平均粒径０．２２μｍのＡｌ２Ｏ３粉末、純度が９９．９５質量％で平均粒径０．４μｍのジルコニア粉末、平均粒径０．６μｍのＴｉＯ２粉末、平均粒径０．６μｍのＭｇ（ＯＨ）２粉末、平均粒径０．５μmのＳｉＯ２粉末、及び平均粒径０．２μｍのＣａＣＯ３粉末を、酸化物換算で、表１に示すような組成になるように秤量混合して、出発原料となる混合粉末を得た。（但し、試料No.11では、ジルコニア粉末として３ｍｏｌ％のＹ２Ｏ３が固溶した安定化ジルコニアの粉末を用いた。） Al 2 O 3 powder having a purity of 99.95% by mass and an average particle size of 0.22 μm, zirconia powder having a purity of 99.95% by mass and an average particle size of 0.4 μm, TiO 2 powder having an average particle size of 0.6 μm, the average particle diameter 0.6μm of Mg (OH) 2 powder, SiO 2 powder having an average particle diameter of 0.5 [mu] m, and the CaCO 3 powder having an average particle diameter of 0.2 [mu] m, in terms of oxide, the composition shown in Table 1 Weighed and mixed to obtain a mixed powder as a starting material. (However, in sample No. 11, stabilized zirconia powder in which 3 mol% of Y 2 O 3 was dissolved was used as the zirconia powder.)
この混合粉末を、１ｔ／ｃｍ２の圧力で金型成形し、さらに３ｔ／ｃｍ２の圧力で静水圧処理を加えて成形体を作製し、表１に示す温度にて、本焼成及び熱間静水圧処理（表中にＨＩＰと表示）を行なった。尚、何れの場合も、本焼成は２時間、熱間静水圧処理は、１時間行った。 This mixed powder is molded at a pressure of 1 t / cm 2 and further subjected to hydrostatic pressure treatment at a pressure of 3 t / cm 2 to produce a molded body. Hydrostatic pressure treatment (indicated as HIP in the table) was performed. In each case, the main firing was performed for 2 hours and the hot isostatic pressure treatment was performed for 1 hour.
得られた各焼結体に対して、曲げ強度(JIS R 1601)、破壊靭性(JIS R
1607)、ビッカース硬度(JIS 2244)を測定し、表１に記載した。また、Ｘ線回折（ＸＲＤ）によってＣａＯによる正方晶ＺｒＯ２が安定化されていることの確認を行い、さらに、透過型電子顕微鏡のエネルギー分散組成分析装置（ＥＤＳ）によりＺｒＯ２へのＣａＯの固溶の確認を行った。
For each sintered body obtained, bending strength (JIS R 1601), fracture toughness (JIS R
1607) and Vickers hardness (JIS 2244) were measured and listed in Table 1. In addition, it was confirmed by X-ray diffraction (XRD) that tetragonal ZrO 2 by CaO was stabilized, and further, CaO was fixed to ZrO 2 by an energy dispersive composition analyzer (EDS) of a transmission electron microscope. The dissolution was confirmed.
表１より、ＺｒＯ２量が本発明の組成範囲より多い試料Ｎｏ．８は、強度と破壊靭性が高いが、硬度が低いことが分かる。また、ＣａＯを含み、他の焼結助剤を含まない材料（試料Ｎｏ．９）は、ＺｒＯ２へＣａの固溶が確認されず、安定化剤としてＣａＯを含まない材料（試料Ｎｏ．１０）と同じく、強度、靭性、硬度がともに低かった。さらに、安定化剤としてＹ２Ｏ３が含まれるＺｒＯ２原料を使用する材料（試料Ｎｏ．１１）は、立方晶ＺｒＯ２含有量が増加し、ＣａＯとＳｉＯ２、ＴｉＯ２、ＭｇＯを含有するにも関わらず強度と靭性が小さかった。しかし、ＣａＯと焼結助剤ＳｉＯ２、ＴｉＯ２、ＭｇＯをそれぞれ特定した量を含み、更に、より低温で焼結した材料（試料Ｎｏ．１、２、４、６及び７）は曲げ強度が１２７０〜１５４０MPａ、破壊靭性４．８〜５．４ＭＰａ・ｍ１／２、硬度１７４０〜１８２０Ｈｖの特性を示した。
From Table 1, sample No. 2 with more ZrO 2 content than the composition range of the present invention. 8 shows that the strength and fracture toughness are high, but the hardness is low. Moreover, the material (sample No. 9) that contains CaO and does not contain other sintering aids is not confirmed as a solid solution of Ca in ZrO 2 (sample No. 10). ), The strength, toughness and hardness were all low. Furthermore, the material (sample No. 11) using the ZrO 2 raw material containing Y 2 O 3 as a stabilizer has an increased cubic ZrO 2 content and contains CaO, SiO 2 , TiO 2 , and MgO. Nevertheless, strength and toughness were small. However, the materials (samples Nos. 1, 2, 4, 6, and 7 ) that contain the specified amounts of CaO and sintering aids SiO 2 , TiO 2 , and MgO, respectively , and are sintered at lower temperatures have bending strength. The characteristics of 1270 to 1540 MPa, fracture toughness 4.8 to 5.4 MPa · m 1/2 , and hardness 1740 to 1820 Hv were exhibited.
Claims (3)
前記原料粉末を所定形状に成形し、
得られた成形体を、１３００℃〜１５００℃の温度範囲で焼成し、
更に前記焼成温度より３０℃以上低い温度で熱間静水圧処理すること、
を特徴とするアルミナ・ジルコニア系セラミックスの製法。 Al is contained in an amount of 72.1 to 80 % by mass in terms of oxide , Zr is contained in an amount of 18 to 25 % by mass in terms of oxide, Ca is contained in an amount of 0.1 to 4% by mass in terms of oxide, and Si is an oxide. 0. 4 to 1.5 mass %, Ti is 0. 3 to 0.7 mass %, Mg is 0. A raw material powder containing 2 to 1.4 % by mass and having a total content in terms of oxides of Si, Ti and Mg in the range of 0.6 to 3.6 % by mass is prepared.
The raw material powder is molded into a predetermined shape,
The obtained molded body was fired at a temperature range of 1300 ° C to 1500 ° C,
Furthermore, hot isostatic pressing at a temperature lower by 30 ° C. or more than the firing temperature,
A process for producing alumina-zirconia ceramics.
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| JPS60204666A (en) * | 1984-03-28 | 1985-10-16 | アイシン精機株式会社 | Aluminum oxide base ceramic material |
| JPS6158857A (en) * | 1984-08-25 | 1986-03-26 | 京セラ株式会社 | High strength alumina sintered body |
| JPH03218967A (en) * | 1989-11-06 | 1991-09-26 | Osaka Cement Co Ltd | High-strength alumina-zirconia-based ceramics sintered body |
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| JPS60204666A (en) * | 1984-03-28 | 1985-10-16 | アイシン精機株式会社 | Aluminum oxide base ceramic material |
| JPS6158857A (en) * | 1984-08-25 | 1986-03-26 | 京セラ株式会社 | High strength alumina sintered body |
| JPH03218967A (en) * | 1989-11-06 | 1991-09-26 | Osaka Cement Co Ltd | High-strength alumina-zirconia-based ceramics sintered body |
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