JPH07102993B2 - Method for manufacturing silicon nitride sintered body - Google Patents

Method for manufacturing silicon nitride sintered body

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Publication number
JPH07102993B2
JPH07102993B2 JP61229101A JP22910186A JPH07102993B2 JP H07102993 B2 JPH07102993 B2 JP H07102993B2 JP 61229101 A JP61229101 A JP 61229101A JP 22910186 A JP22910186 A JP 22910186A JP H07102993 B2 JPH07102993 B2 JP H07102993B2
Authority
JP
Japan
Prior art keywords
sintered body
silicon nitride
hip
phase
defects
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
JP61229101A
Other languages
Japanese (ja)
Other versions
JPS6385050A (en
Inventor
尚登 広崎
明 岡田
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nissan Motor Co Ltd
Original Assignee
Nissan Motor Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nissan Motor Co Ltd filed Critical Nissan Motor Co Ltd
Priority to JP61229101A priority Critical patent/JPH07102993B2/en
Publication of JPS6385050A publication Critical patent/JPS6385050A/en
Publication of JPH07102993B2 publication Critical patent/JPH07102993B2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Description

【発明の詳細な説明】 <産業上の利用分野> 本発明は、耐熱性,機械的特性に優れ、化学的に安定な
ため、自動車用エンジン部品などへの適用が進められて
いる窒化珪素質焼結体に関するものである。
DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention has excellent heat resistance, mechanical properties, and is chemically stable. Therefore, it is being applied to automobile engine parts, etc. It relates to a sintered body.

<従来の技術及び発明が解決しようとする問題点> 従来の窒化珪素質焼結体の製造法としては、反応焼結
法,ホツトプレス法,常圧焼結法,ガス圧焼結法などが
知られているが、エンジン部品などの高強度が必要な複
雑形状部品には常圧およびガス圧焼結法が適している。
これらの方法は、窒化珪素原料粉末にMgOなどの酸化物
系焼結助剤を添加した混合粉末を、ラバープレス,スリ
ツプキヤスト,射出成形などの方法により成形した後
に、窒素ガス1気圧(常圧焼結法)または1気圧以上
(ガス圧焼結)の雰囲気下で加熱する工程による。
<Problems to be Solved by Conventional Techniques and Inventions> Reactive sintering methods, hot pressing methods, atmospheric pressure sintering methods, gas pressure sintering methods and the like are known as conventional methods for producing a silicon nitride sintered body. However, atmospheric pressure and gas pressure sintering methods are suitable for complex shaped parts that require high strength, such as engine parts.
In these methods, a mixed powder in which an oxide-based sintering aid such as MgO is added to silicon nitride raw material powder is molded by a method such as rubber press, slip cast, injection molding, etc. Sintering method) or a step of heating in an atmosphere of 1 atm or more (gas pressure sintering).

しかしながら、粉末の成形工程で空孔、亀裂などの成形
欠陥が発生すると、これらの欠陥は焼成後も焼結体中に
残り、製品の強度を低下させるため、平均強度が低くま
た、強度のばらつきも増大することが知られている。
However, when molding defects such as voids and cracks occur in the powder molding process, these defects remain in the sintered body even after firing, reducing the strength of the product, resulting in a low average strength and variations in strength. Is also known to increase.

焼結体中の欠陥を低減する方法として熱間静水圧プレス
(以下HIPと略す)処理が知られている。これは、高温
にて焼結体に高圧のガスを作用させることにより、空孔
欠陥をおしつぶすことを狙いとしている。しかしなが
ら、従来の窒化珪素焼結体に対してはこの効果は小さか
つた。これは次の理由による。
Hot isostatic pressing (hereinafter abbreviated as HIP) treatment is known as a method for reducing defects in the sintered body. This aims at crushing the vacancy defects by causing a high-pressure gas to act on the sintered body at a high temperature. However, this effect was small for the conventional silicon nitride sintered body. This is for the following reason.

従来、窒化珪素原料粉末としてはα型を主成分とするも
のを出発原料とし、焼成中にち密化と同時にα相からβ
相への転移を起こさせ(このときβ相が針状化する)、
針状相を多く含む窒化珪素質焼結体を得ることが一般に
行われていた。これは、針状相を多く含む焼結体は、一
種の複合材料であり、破壊じん性,強度等が優れている
と考えられていたためである。しかしながら、これをHI
P処理しても欠陥の囲りの針状結晶が欠陥の変形を防げ
るため、欠陥がつぶれにくいという欠点があつた。
Conventionally, as a starting material, a silicon nitride raw material powder whose main component is α type is used, and during the firing, the powder is densified and the α phase to β
Causes a transition to the phase (at this time the β phase becomes acicular),
It has been generally practiced to obtain a silicon nitride-based sintered body containing a large amount of acicular phases. This is because the sintered body containing many acicular phases was a kind of composite material and was considered to have excellent fracture toughness, strength and the like. However, HI
Even if the P treatment is performed, the acicular crystals surrounding the defect prevent deformation of the defect, and thus the defect is difficult to collapse.

<問題点を解決するための手段> 本発明者らは、この欠点を取り除くべく研究を進めたと
ころ、窒化珪素の出発原料としてα相主体のものに替え
て、β相を70%以上含む窒化珪素を用い、これに通常用
いられる焼結助剤を加え混合、成形の後、1600℃以上の
温度で500気圧以下の窒素雰囲気下で処理し、次いで、
熱間静水圧プレス処理することにより、成形体中に欠陥
を含んでいてもHIP処理によりそれを取り除くことがで
き、高強度かつばらつきの少ない窒化珪素質焼結体の製
造方法の発明に到つた。
<Means for Solving Problems> The inventors of the present invention have conducted research to eliminate this drawback. As a starting material of silicon nitride, the nitriding material containing 70% or more of β phase instead of α phase mainly Using silicon, adding a sintering aid that is usually used to this, mixing, molding, and then treating at a temperature of 1600 ° C. or higher in a nitrogen atmosphere of 500 atm or lower, and then
By hot isostatic pressing, even if the compact contains defects, it can be removed by HIP treatment, leading to the invention of a method for producing a silicon nitride sintered body with high strength and little variation. .

すなわち、原料粉末としてβ相を70%以上含む窒化珪素
粉末を用いることにより、αからβへの転移する量が低
減するため針状結晶の量が減少し、HIPが有効に働く様
にすることを狙いとした。
That is, by using silicon nitride powder containing 70% or more of β phase as the raw material powder, the amount of α-to-β transition is reduced, so that the amount of needle-like crystals is reduced and HIP works effectively. I aimed at

本発明では、窒化珪素原料粉末は、β相を70%以上含む
ものを使用する。残りは、α相またはアモルフアスでよ
い。β相が50%未満では焼結体中に針状結晶が多く存在
するためHIPの欠陥除去効果が減少する。β相100%を出
発原料としても本発明は有効であるが、焼結体の強度を
要求する場合は、HIP効果を防げない範囲でα相を含む
原料が良い。次に、焼結助剤は窒化珪素の一般の常圧焼
結で使用される助剤、例えば、MgO,Y2O3−Al2O3,などを
窒化珪素粉末と助剤との合計重量中約7〜15重量%の割
合で使用することができる。
In the present invention, the silicon nitride raw material powder contains 70% or more of β phase. The balance may be alpha phase or amorphous. If the β phase is less than 50%, many needle-like crystals are present in the sintered body, so that the HIP defect removal effect is reduced. The present invention is effective even if 100% of β phase is used as a starting material, but when strength of the sintered body is required, a material containing α phase is preferable as long as the HIP effect cannot be prevented. Next, the sintering aid is an additive used in general pressureless sintering of silicon nitride, for example, MgO, Y 2 O 3 -Al 2 O 3 , etc. is the total weight of the silicon nitride powder and the additive. It can be used in a proportion of about 7 to 15% by weight.

成形は、金型成形,ラバープレス,スリツプキヤスト、
射出成形などセラミツクスの一般的な成形法によればよ
い。
Molding is mold molding, rubber press, slip cast,
A general ceramic molding method such as injection molding may be used.

次に、焼成は500気圧以下の窒素で、1600℃以上の温度
にて行われる。500気圧を越える圧力では、閉気孔に閉
じ込められた高圧ガスにより終期焼結が阻害されるため
ち密な焼結体が得られない。焼成温度は、使用する焼結
助剤の種類,量などにより異るが、1600℃未満では、液
相が生成しないため、ち密化しない。上記工程における
窒素雰囲気圧の下限、焼成温度の上限は特にないが、だ
いたいのめどとして、窒素雰囲気圧は1気圧以上、焼成
温度は約2200℃以下くらいで上記処理を行うのがよい。
Next, calcination is carried out at a temperature of 1600 ° C. or higher with nitrogen of 500 atm or lower. When the pressure exceeds 500 atm, a dense sintered body cannot be obtained because the high-pressure gas trapped in the closed pores hinders final sintering. The firing temperature varies depending on the type and amount of the sintering aid used, but below 1600 ° C, the liquid phase does not form, and therefore it does not become dense. The lower limit of the nitrogen pressure in the above step, the upper limit of the calcination temperature is not particularly as a rule of prospects, nitrogen atmosphere pressure is more than 1 atm, the firing temperature may be carried out the process at about about 2200 ° C. or less.

HIPは、1600℃以上で行われる。1600℃未満では焼結体
の組成変形が少なく欠陥除去の効果が少ない。また、こ
の場合も温度の上限は特にないが、一般に窒化珪素質焼
結体の焼結温度の上限と考えられている約2200℃以下程
度でHIPを行うのがよい。ガスの種類および圧力は特に
限定しないが、カプセルフリーで処理を行う場合は窒素
ガスの使用がよい。またガス圧力は500気圧以上で特に
効果がある。さらに本発明では、500気圧以下での焼
成後ガラス等のカプセルで試料を密閉する方法、焼成
とHIPを別の装置で行う方法HIP装置で、温度と圧力を
制御することにより焼成とHIPを行う方法、などで処理
を行うことができる。
HIP is performed above 1600 ° C. If it is less than 1600 ° C, compositional deformation of the sintered body is small and the effect of defect removal is small. Also in this case, the upper limit of the temperature is not particularly limited, but it is preferable to perform the HIP at about 2200 ° C. or lower which is generally considered to be the upper limit of the sintering temperature of the silicon nitride sintered body. The kind and pressure of the gas are not particularly limited, but nitrogen gas is preferably used when the capsule-free processing is performed. The gas pressure of 500 atm or higher is particularly effective. Further, in the present invention, a method of sealing a sample with a capsule such as glass after firing at 500 atm or less, a method of performing firing and HIP in another device, a HIP device, performing firing and HIP by controlling temperature and pressure. The processing can be performed by a method or the like.

<実施例> 以下に本発明の実施例を掲げる。<Examples> Examples of the present invention will be given below.

実施例1 β相70%残部α相からなるSi3N4粉末に10%のMgOを添加
し、ボールミル混合した後、乾燥,粉砕した。この混合
粉末に欠陥源として70μmのプラスチツク球を0.1vol%
添加し、20MPaで金型成形後200MPaでラバープレスした
後500℃に加熱してプラスチツクを燃焼除去することに
より、5×6×50mmの形状の欠陥入り成形体を得た。こ
れを、窒素1気圧の雰囲気下で1700℃で1時間焼成し
た。この試料の一部を、窒素2000気圧の雰囲気下で1700
℃で1時間熱間静水圧プレスを施した。焼成のみおよび
HIP処理の試験片を研削加工し3×4×40の形状にし
て、スパン30mmにて常温曲げ試験を行つた各15本の平均
強度結果を表1に示す。第1表の様に、HIP処理により
強度は向上した。また、破面観察によれば、HIPなしで
は球状欠陥を起点として破壊していたが、HIP処理した
試験片では球状欠陥は見られなかつた。
Example 1 10% MgO was added to Si 3 N 4 powder consisting of the β phase 70% and the remaining α phase, mixed by a ball mill, dried and pulverized. 0.1 vol% of 70 μm plastic spheres as a defect source in this mixed powder
The mixture was added, molded with a die at 20 MPa, rubber-pressed at 200 MPa, heated to 500 ° C. to burn off plastics, and a molded body with defects of 5 × 6 × 50 mm was obtained. This was fired at 1700 ° C. for 1 hour in an atmosphere of nitrogen at 1 atm. A portion of this sample was placed at 1700 in a nitrogen atmosphere of 2000 atm.
Hot isostatic pressing was carried out at 0 ° C for 1 hour. Firing only and
Table 1 shows the average strength results of 15 pieces each of which was subjected to a room temperature bending test with a span of 30 mm by grinding a HIP-treated test piece into a shape of 3 × 4 × 40. As shown in Table 1, the strength was improved by the HIP treatment. Further, according to the fracture surface observation, it was found that the fracture was initiated from the spherical defect without HIP, but no spherical defect was found in the HIP-treated test piece.

比較例1 α相93%からなるSi3N4粉末を用いた他は、実施例1と
同じ工程で処理し、曲げ試験を行つた結果を表2に示
す。第1表の様にHIP処理による強度向上は少なく、ま
た、HIP後も焼結体中に球状欠陥が残つていた。
Comparative Example 1 Table 2 shows the results of a bending test performed by the same process as in Example 1 except that Si 3 N 4 powder consisting of α phase 93% was used. As shown in Table 1, the strength improvement by HIP treatment was small, and spherical defects remained in the sintered body even after HIP.

実施例2〜4 表1に示す組成の原料を用い、実施例1と同じ工程で欠
陥を導入し、表1の条件で焼成、HIPを行つた。表1に
示す様に強度向上が見られ、球状欠陥も消滅した。
Examples 2 to 4 Using the raw materials having the compositions shown in Table 1, defects were introduced in the same steps as in Example 1, and firing and HIP were performed under the conditions shown in Table 1. As shown in Table 1, the strength was improved and the spherical defects disappeared.

比較例2〜4 表2に示す組成の原料を用い、実施例1と同じ工程で欠
陥を導入し、表2条件で焼成、HIPを行つた。表2に示
す様に強度向上は少なく、またHIP後も焼結体中に球状
欠陥が見られた。
Comparative Examples 2 to 4 Using the raw materials having the compositions shown in Table 2, defects were introduced in the same steps as in Example 1, and firing and HIP were performed under the conditions of Table 2. As shown in Table 2, there was little improvement in strength, and spherical defects were found in the sintered body even after HIP.

実施例5 β相70%残部α相からなる粉末に、10%Y2O3,5%Al2O3
となるように助剤を添加し、ボールミル混合後乾燥,粉
砕し、混合粉末を得た。混合粉末に有機物バインダーを
添加し混練した素地を射出成形し、φ20mm長さ50mmの成
形体を得た。これを500℃に加熱し有機物バインダーを
除去したものをX線で観察したところ、内部に成形欠陥
が見えた。これを、N2ガス圧下で第1図に示すスケジユ
ールにて処理し、得られた焼結体をX線観察したとこ
ろ、欠陥は消滅した。
Example 5 10% Y 2 O 3 , 5% Al 2 O 3 was added to a powder consisting of β phase 70% and the balance α phase.
Auxiliary agents were added so as to obtain the following, and the mixture was ball-milled, dried and pulverized to obtain mixed powder. An organic binder was added to the mixed powder and the kneaded material was injection-molded to obtain a molded body having a diameter of 20 mm and a length of 50 mm. When this was heated to 500 ° C. and the organic binder was removed and observed by X-ray, molding defects were found inside. This was treated with the schedule shown in FIG. 1 under N 2 gas pressure, and the obtained sintered body was observed by X-ray. As a result, the defects disappeared.

<発明の効果> このように、本発明によれば、成形工程で欠陥が発生し
ても、焼成中にそれを取り除くことができ、欠陥のない
緻密で高強度の焼結体が得られる。
<Effects of the Invention> As described above, according to the present invention, even if a defect occurs in the molding step, it can be removed during firing, and a dense and high-strength sintered body having no defect can be obtained.

【図面の簡単な説明】[Brief description of drawings]

第1図は、この発明の実施例5を製造する際の焼成温
度、圧力−時間の関係を示すグラフである。
FIG. 1 is a graph showing the relationship between firing temperature and pressure-time when producing Example 5 of the present invention.

Claims (1)

【特許請求の範囲】[Claims] 【請求項1】β相を70%以上含む窒化珪素粉末と焼結助
剤とを混合、成形した後、1600℃以上の温度で窒素雰囲
気中、500気圧以下にて処理し、次いで、1600℃以上の
温度で熱間静水圧プレス処理することを特徴とする窒化
珪素質焼結体の製造方法。
1. A silicon nitride powder containing 70% or more of β phase and a sintering aid are mixed and shaped, and then treated at a temperature of 1600 ° C. or more in a nitrogen atmosphere at 500 atm or less, and then at 1600 ° C. A method for producing a silicon nitride sintered body, comprising performing hot isostatic pressing at the above temperature.
JP61229101A 1986-09-27 1986-09-27 Method for manufacturing silicon nitride sintered body Expired - Fee Related JPH07102993B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP61229101A JPH07102993B2 (en) 1986-09-27 1986-09-27 Method for manufacturing silicon nitride sintered body

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP61229101A JPH07102993B2 (en) 1986-09-27 1986-09-27 Method for manufacturing silicon nitride sintered body

Publications (2)

Publication Number Publication Date
JPS6385050A JPS6385050A (en) 1988-04-15
JPH07102993B2 true JPH07102993B2 (en) 1995-11-08

Family

ID=16886761

Family Applications (1)

Application Number Title Priority Date Filing Date
JP61229101A Expired - Fee Related JPH07102993B2 (en) 1986-09-27 1986-09-27 Method for manufacturing silicon nitride sintered body

Country Status (1)

Country Link
JP (1) JPH07102993B2 (en)

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5888171A (en) * 1981-11-17 1983-05-26 株式会社神戸製鋼所 Manufacture of high density silicon nitride sintered body

Also Published As

Publication number Publication date
JPS6385050A (en) 1988-04-15

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