Selection and qualification of materials for relative motion and electrical isolation in a vacuum environment

Coefficient of friction and wear rate were determined under conditions of reciprocative sliding in vacuum for a number of state-of-the-art hard coatings, including oxides, nitrides and carbides. These materials were tested in contact with one another and against the alloys Inconel 718 and Nitronic 60. For some selected conditions, similar tests were conducted in air to enable environmental influence to be assessed. The program also investigated cyclic compression loading of coated surfaces against uncoated Inconel 718. The results are reported and were used to select and qualify coating materials for limiter component applications that operate both in vacuum and in low pressure hydrogen at elevated temperature in the tokamak fusion test reactor. (Auth.)