Vacuum Bearings with Dry Lubrication

Extreme environment for bearings

High vacuum and temperatures up and above 500° C (approx. 932° F) exclude conventional oil or grease lubrication systems. Function, reliability and life-time of the bearing components are ensured by tribologic solid lubricant layers and systems.

The bearing components like rings, balls and cages are manufactured from heat resistant high speed tool steel or alloys (e.g. NiBe2). As an alternative, GMN offers hybrid bearings with ceramic components (e.g. balls made from Si3N4).

Solid lubrication:

For physically coating of bearing components with tribologic layers GMN uses a PVD sputter coating machine and plasma cleaning device for preliminary treatment.

Depending on application and requirements, the layers serve as wear protection, separating medium to prevent cold welding, transfer- and minimum lubrication, combined with emergency running properties. The friction coefficients range from 0,01 to 0,25 at temperatures up to 500° C (approx. 932° F).

The tolerances of the work piece are not affected by the small thickness of the layer.

For more information about sputter technology applications please go to technology and example.

Development:

GMN carries out further developments and investigations on tribological layer technology in co-operation with research partners like the university of Erlangen and the technical university of Darmstadt. The influences of substratum characteristics as roughness, surface morphology, structural composition as well as layer-characteristics like nucleus formation, crystallization, adhesion, microstructure and internal stress have to be investigated and understood.

For description of tribologic layers, bonding mediators respectively interlayers, GMN uses electron scan microscopy, X-ray and electron diffraction. For investigation of wear behavior GMN works with high temperature, high vacuum tribometer and four ball tester.

Technology

PVD-Equipment at GMN:

State of the art magnetron PVD-sputter technology with coating chamber optimized for bearing components. Custom designed substratum holders for the efficient deposition on complex 3-dimensional surfaces without mechanical influences.

PVD Equipment

Characteristics and advantages of PVD-coating:

  • General: possibility of deposition of a wide range of materials, such as metals, semiconductors or ceramics, in spite of melting point or vapor pressure.
  • Coating of layers without exceeding a critical temperature of the substratum.
  • Equal layers, high bonding strength at high growth-rates.
  • Layer thickness from a few nanometers (10-9 m) up to microns (10-6 m).
  • Minimum amount of chemical waste

Solid lubricants for GMN bearings:

  • Silver (Ag),
  • Lead (Pb)
  • Gold (Au)
  • Molybdenum disulphide (MoS2)

Bonding layer or co - sputtered materials for stabilization of functional layer:

  • Chrome-nickel steel
  • Copper
  • Titanium

precision radial ball bearings

Physical principle:

The solid lubricant is sputtered from a magnetron sputter source and deposited as a thin layer on the surface of the substratum.

Ions of the process gas (basically argon) are accelerated and shot on the negative charged target which consists of the coating material. Caused by the high energy of these striking ions, the target atoms are sputtered on the surface. These atoms in a gaseous condition condense on the substratum to be coated and leave a thin lubrication film.

Supported by an additional bias voltage, ionized parts can be accelerated in direction of the substratum, where the sputtered atoms can be plated more strongly on the surface.


precision radial ball bearings

Plasma Cleaning:

Before coating the bearing components must be refined to create a reactive, clean metal surface. GMN uses plasma cleaning equipment. The parts are cleaned on a water or hydrocarbon basis followed by vacuum drying and oxygen - plasma - cleaning.

Examples & Applications

Special applications for GMN bearings with dry lubrication

  • Vacuum technology, like electron-scan microscopes, turbo-molecular pumps
  • Air - and spacecraft applications
  • Semiconductor productions
  • Medical applications, for example X-ray tubes

Industrial Bearing

Bearing design:

  • Rings and balls from high temperature tool steel
  • Ceramic balls (Si3N4)
  • Cage material heat resistant steel

Vacuum Bearing

Bearing design:

  • Rings and balls from high temperature tool steel
  • Cage material heat resistant steel

Precision Vacuum Bearing

Bearing design

  • Rings, balls and cage made from heat resistant steel
  • Rings completely gold plated (Au, PVD sputtered)

Lubrication:

  • Dry

Bearing

Bearing design:

  • Back-to-back preloaded spindle bearing pair
  • Rings and balls made from SAE 52100 (100Cr6)
  • Rings completely gold plated (Au, PVD sputtered)

Lubrication:

  • Special vacuum oil

Bearing

Bearing design:

  • Rings and balls made from SAE 52100 (100Cr6)
  • Full ball complement
  • Rings completely gold plated (Au, PVD sputtered)

Solid lubrication:

  • Rings MoS2-coated
  • Balls MOVIC® treated

Application:

  • Emergency bearings (touchdown bearing)

Installation

vacuum ball bearing installation

Depending on the demand and future installation specifications of a vacuum application, the bearings receive special treatments, package and transportation.

  • For vacuum applications a complete plasma cleaning is required.
  • Plasma cleaned parts must be packed in vacuum containers.

For certain applications, the bearings must be stored in nitrogen filled boxes. GMN should be informed about the assembly conditions.

It must be guaranteed that the coating will not be damaged during handling and assembly. GMN offers assistance for correct handling.


A table specifying the operation, i.e. temperature, vacuum pressure, atmosphere (active or reactive gases), speed and the expected lifetime can be established in co-operation with GMN.


Click here or call 1.800.323.5725 to Request a quote

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