技術情報

2001  Volume 33 

The Effect of Oxygen Introduction on Oxidation Resistance and Cutting Performance of Si3N4 Ceramics 窒化珪素セラミックスの耐酸化性と切削性能に及ぼす酸素導入の効果
Kokoro GOTO*1), Mituyoshi NAGANO*2), Hideaki SANO*1), Shigeya SAKAGUCHI*2)
*1) Department of Materials Science and Engineering, Faculty of Engineering, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan
*2) Nippon Tungsten Co., Ltd. 3173-2 Oaza-sonobe, Kiyama-cho, Miyaki-gun, Saga 841-0203, Japan
後藤こころ、永野光芳、佐野秀明、坂口茂也、内山休男
Key words Si3N4 ceramics, oxidation, sintering, powder, Al2O3 , solid solution, cutting tool
キーワード 窒化珪素、セラミックス、酸化、焼結、粉末、アルミナ、固溶、切削工具

Abstract

Si3N4 ceramics used in this study were introduced to oxygen during preparation by three different methods; (1) pre-oxidation of raw powder, (2) sintering in different atmospheres, (3) controlling the amount of Al2O3 to be added as a sintering additive. Their oxidation behavior in term of change in mass, morphology surface composition and cross-section of the specimen, was studied between temperature of 1200 and 1400°C. Though mass change could hardly be seen below 1300°C, it was observed remarkably at 1400°C. In isothermal oxidation at 1400°C, as the amount of Al2O3 increases from 2mass% to 4mass%, the mass of the specimen also increases. However, the effect of pre-oxidation of raw powder and sintering in different atmospheres does not appear on oxidation resistant Si3N4 ceramics. Oxidized layers were formed on the surface of the specimen and they consist of two or three layers. Those specimens which had lower Al and O atom solid solution was superior to higher solution specimens, because lower solid solution specimens have greater hardness and strength. As a result, it was considered preferable that Al and O atom solid solution should be lower in the range of sinterability accerelation.
(1)粉末酸化、(2)焼結雰囲気、(3)焼結助剤のアルミナ添加量という3つの方法で酸素導入を行なった酸素固溶量の異なる窒化珪素セラミックスの耐酸化性と切削性能に関して検討を行なった。耐酸化性に関しては、1200 - 1400 ℃の範囲で調査したが、1400℃で酸化挙動が顕著となり、Al2O3 の添加量が多くなるにしたがって、酸化による重量増加が大きかった。しかしながら、粉末酸化や焼結雰囲気からの酸素導入が耐酸化性に及ぼす影響は顕著に表れなかった。切削性能評価では、Al2O3 の添加量が多くなるにしたがって摩耗が大きくなる傾向にあり、酸素導入による影響よりも大きい傾向にあった。
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