TRIBOLOGICAL BEHAVIOR OF MATERIALS AT CRYOGENIC TEMPERATURES

Up to now interest in low temperature technology has been restricted t o applications in space technology and superconductivity. However, som e applications of cryotechnology are ready to take off in the near fut ure. One example is the utilization of liquid hydrogen as an environme ntally friendly energy carrier for transportation and energy supply sy stems. This technology involves new problems concerning the strength o f materials as well as safety of equipment. For example, in hydrogen-f uelled aircraft, materials such as austenitic stainless steels or copp er which are widely used in cryotechnical applications must be minimiz ed or substituted because of their high density. On the other hand, th e properties of light-weight materials, especially advanced composites , have not been examined sufficiently in cryogenic environment. Agains t this background, at the Federal Institute of Materials Research and Testing investigations on the low temperature behaviour of materials w ere started, including tribological investigations. It is the aim of t he project to acquire data on materials' properties when stressed at l ow temperature and especially in low temperature gaseous hydrogen and liquid hydrogen. In addition to the thermal conditions, cryotechnical applications are also characterized by special environments. Different cryotribometers were constructed for different cooling and loading co nditions as well as different environmental media in the temperature r ange from 4.2 K up to room temperature. Results are presented of low t emperature investigations on the tribological behaviour of polymers an d composites as well as of TiN and carbon coating systems. (C) 1998 El sevier Science S.A. All rights reserved.