Fabrication of Si3N4 Vacuum Pump Rotor by Bonding.

Research and Development of Si3N4 turbo-viscous vacuum pump rotor were conducted. It is difficult to fabricate this type of the rotor by machining of monoblock Si3N4 because it's shape is complex. So, bonded construction in which disks and axle were located by the connection of projection and bore was applied to fabrication after disks and axle were separately sintered and machined.Main results obtained are as follows.(1) 80wt%Cu-20wt%Ti brazing was chosen for bonding method because joint strength properties at room temperature -773 K were excellent.(2) It was predicted by calculation of stress that high stress generated in bonding joint near the connection of projection and bore at high speed rotating. From this calculation result, restriction of bonding area which was not brazed this high stress area was applied so that reliability of rotating characteristic could be raised.(3) Si3N4 turbo-viscous vacuum pump rotor fabricated with above mentioned method rotated by peripheral speed 196 m/s at spin test. From this spin test result, it was confirmed that ceramic vacuum pump rotor could be alterable for metal vacuum pump rotor.