Low temperature tribometers and the behaviour of ADLC coatings in cryogenic environment

In a cryogenic environment components with interacting surfaces in relative motion (tribosystems) like bearings, seals and valves often generate undesired heat and experience high wear. Because conventional lubricants like oils or greases cannot be used in this temperature range, solid lubricants or materials with good frictional properties in unlubricated operation must be used. To test the suitability of conventional and advanced materials for tribosystems in this extreme environment and to obtain reliable materials data, model friction tests at low temperatures are performed. In most of the tests the samples are in ball-on-disc-configuration but various methods for cooling, loading, and measurement are applied. As an example the test results for amorphous carbon coatings in the temperature range 10–77 K are presented. These coatings can be suitable for cryogenic tribosystems, but their behaviour strongly depends on the composition and deposition method.