Materials Research for Advanced Inertial Instrumentation. Task 2. Gas Bearing Material Development.
Research rept. 1 Oct 80-30 Sep 81,
CHARLES STARK DRAPER LAB INC CAMBRIDGE MA
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The gas bearing materials development program includes three approaches chemical vapor deposition and subsequent reactive diffusion of boron on beryllium, ion implantation of boron into beryllium, and development of a beryllium-ceramic composite material. The chemical vapor deposition CVD process at higher temperatures of 850 to 950 C produced thin, hard, multiphase coatings compared to thicker coatings of boron at lower temperatures of 700 to 800 C. No deterioration of quality was observed upon increasing the sample size. Conventionally machined, and subsequently stress-relieved, beryllium discs were polished and implanted with boron. Experiments showed that for an identical surface concentration a flat boron profile was substantially superior in terms of resisting wear, compared to a graded boron distribution. This indicated that the wear mechanism was strongly influenced by what existed in the subsurface regions in addition to the conditions in the immediate region of contact. Differences were observed for the friction traces of the implanted specimens with respect to beryllium. Additional lapping studies were performed during this reporting period on the Be-TiB2 materials with fine diamond particles as the abrasive medium. The use of diamond resulted in damage observed primarily as pits in the TiB2 particles dispersed in the composite.
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