| 摘要 |
PURPOSE:To prevent damage caused by the gall of rotors by giving plating containing a material which relieves said gall to the contacting parts of said rotors which cooperatively feed and discharge fluid, with a fluid. CONSTITUTION:In a screw vacuum pump, an alloy plating of Ni-W-P or NI-W-B is given to either of a male rotor 12 and a female rotor 13 which cooperatively feed and discharge fluid, and an alloy plating of Ni-Cu-P or Ni-Cu-B containing Cu which has high ductility and which is apt to form an immovable film on the surface is given to the other. By this structure, since an alloy plating containing Cu is given to one of the rotors 12, 13, the gall between rotors 12, 13 themselves can be relieved. And, the Ni-W-P and Ni-W-B alloys having high corrosion resistance also prevent the corrosion of the rotors 12, 13.
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