酸化物超電導セラミックスの放電加工 (第1報)
加工表面の物性的特性の変化
1993 年 27 巻 54 号 p. 32-42
詳細
1993 年 27 巻 54 号 p. 32-42
Oxide-superconductor ceramics can be machined by EDM, since these ceramics have an electrical conductivity at room temperature. However, change in physical properties of the machined surface due to the heating effect of electric dischage is supposed to occur, because oxide-superconductors are known to be unstable at temperatures above 450°C.
In this study, EDM is performed on Ba2YCu3O7-δ superconductor ceramics using a RC discharge circuit, and some physical properties of machined surfaces and machined chips are investigated by means of SEM, X-ray deffraction and electric conductivity measurement. Results obtained are as folloes: (1) A degenerated layer is formed on the machined surface, probably due to resolidification of the melted surface layer. This layer has a high resistivity compared with that of the bulk material. (2) Machined chips, generated by EDM, have an amorphous structure and extremely high resistivity (-103Ω·cm). (3) with the formation of a degenerated layer on the machined surface, peak value of the discharge current decreases down to 75% of the initial value.
