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)

Instal