号数 ばね論文集４５号（２０００年）
ページ数 pp.19-23
種類 論文
論文名 ばね用窒化珪素/SiC複合セラミックスき裂治癒材の疲労強度特性
Title Cyclic Fatigue Strength of Crack-healed Si3N4/SiC Composite Ceramics for Spring
著者 Feiyuan YAO1)・安藤 柱1)・Min-Cheol CHU1)・佐藤 繁美2)
Author Feiyuan YAO1)・Kotoji ANDO1)・Min-Cheol CHU1)・Shigemi SATO2)
抄録 窒化珪素セラミックスのき裂治癒特性とき裂治癒部の高温強度についてすでに系統的に調査した。本論文は、窒化珪素セラミックス治癒材の繰返し疲労強度特性について詳しく調べたものである。本研究に用いた供試材は、焼結助剤としてY2O38wt.%を添加したものとY2O35wt.%、Al2O33wt.%を添加したものの二種類Si3N4/SiC複合材である。本論文中ではそれぞれSNS-Y8とSNS-Y5A3と呼ぶ。Vickers硬度計を用いて試験片の中央部に半楕円き裂を導入した(平均直径は100μmと200μmである)。その後、予き裂材に大気中、1200℃〜1300℃,１時間の熱処理を施してから、室温で繰返し疲労強度を測定した。き裂治癒材は優れた疲労強度特性を示し、平滑材とほぼ同程度の疲労強度を示した。 2×106回繰返し疲労を経って破断しなかった試験片に対して、SEMでその表面状態を観察した結果、新たなき裂が発生しなかったことがわかった。
Abstract Crack-healing behavior of silicon nitride ceramics and high temperature strength of crack-healing zone have been investigated previously systematically in our last work. In this paper, the cyclic fatigue strength behavior of crack-healed ceramics was investigated in detail. Two kinds of the compositions of Si3N4 and SiC with different sintering additive were tested. One contains the 8wt.% Y2O3 as a sintering additive, and was called SNS-Y8 specimen in this paper, another contains the 5wt.% Y2O3 and 3wt.% Al2O3 as a sintering additive, and was called SNS-Y5A3 specimen in this paper. The semicircular crack (average diameter is 100μm and 200μm)was made in the center of specimen using Vickers hardness indenter. Cracked specimen were heat-treated at 1200ºC〜1300ºC for 1 hour in the air. Cyclic fatigue strength test was conducted at room temperature. Crack-healed material has shown the outstanding fatigue strength behavior and attains almost the same strength as smooth specimen do. The surface state of the specimen which did not fail for cyclic fatigue experiments of 2×106 cycles was observed by SEM., any new crack was not found on the surface of crack-healed specimen which survived fatigue test of 2×106 cycles.
著者の所属 1)横浜国大　2)日本発条(株)
Belonging 1)Yokohama National University 2)NHK SPRING Co, Ltd.
Key Words Ceramics , Crack-healing, Silicon nitride, Sintering additive, Semicircular crack, Fatigue strength, Strength recovery.