| Project/Area Number |
16560598
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Inorganic materials/Physical properties
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| Research Institution | The National Maritime Research Institute |
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Principal Investigator |
SENDA Tetsuya National Maritime Research Institute, Principal Research Coordinator., 企画部, 研究統括主幹 (80344240)
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| Co-Investigator(Kenkyū-buntansha) |
MURAKAMI Kenji National Maritime Research Institute, Materials Engineering Group, Head, 輸送高度化研究領域, 新材料研究グループ長 (60112067)
KAWAGOE Yo-ichi National Maritime Research Institute, Materials Engineering Group, Senior Researcher, 輸送高度化研究領域新材料研究グループ, 主任研究員 (90415810)
ADACHI Koshi Tohoku University, School of Mechanical Engineering, Associate Professor, 大学院・工学研究科機械電子工学専攻, 助教授 (10222621)
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| Project Period (FY) |
2004 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 2005: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2004: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Keywords | alumina / tribology / electron microscopy / microatructure / 塑性変形 / 摩耗メカニズム |
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| Research Abstract |
Alumina is promising for a use as a material of high wear resistance. A specific wear rate less than 10^<-6>mm^3/Nm (mild wear) has been reported under a certain condition whereas a high specific wear rate of 10^<-3> to 10^<-5>mm^3/Nm (severe wear) have been observed under other conditions. This study is focused on the mechanisms of these two wear regimes, and microstructural difference between these two situations is investigated in detail. Wear tests were performed under various loads, at various temperatures and for various distances using alumina discs and balls of purities of 99.9% and 99.5% which exhibit a different microstructure.
At room temperature, it was in the mild wear regime when the load was less than 40 N, but it was in the severe wear regime where extensive grain boundary microfracture was observed for a load of 50 N. This transition did not clearly depend on the microstructure or grain size. Heating the specimen to a high temperature of 200℃ to 500 ℃ resulted in a transition to the severe wear even for a load of 5N.
TEM observations have revealed that microstructure of the surface region of mild wear specimens shows a layer structure and that an amorphous-like (less crystalline) phase is observed at the top layer. An electron diffraction study on this region suggests that γ-alumina is the most possible phase. A relatively soft layer formed on the hard α-alumina substrate may exhibit a lubrication effect to prevent a severe microfracture resulting in a mild wear. At the surface in the severe wear regime, a similar layer consisting of fine particles is observed. However, phase studies show that the particles are highly deformed α-alumina, same phase as the substrate, suggesting that the layer is probably formed as a compact of debris particles. It is concluded that a layer of lower hardness on the surface may be critical to the mild wear regime occurring in alumina sliding contact.
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