THE THERMOCHEMICAL STABILITY OF CARBON-CARBON USING AN ANTIOXIDATION COATING FOR BURAN .2

The thermochemical stability of carbon-carbon material with an antioxi dation coating for ''Buran's'' nose tip and leading edges was investig ated using subsonic free jets of pure air. Two induction plasma genera tors of 60-kW and 500-kW power were used in these experiments. Univers al and ''high productive'' facility of 60-kW power were used for testi ng of little disk samples of 30 mm diameter in wide range of physical parameters. For example, the range of smooth pressure regulation is 0. 05 - 1.0 x 10(5) Pa. The effect of temperature, pressure, and the numb er of testing cycles influence on mass loss flux was established. Thes e results were combined with SEM, analysis of boundary layer optical s pectra, and tests in dissociated nitrogen. Conclusions were drawn rega rding the main physicochemical processes which take place during the i nteraction of dissociated air with the coating and material. The effec t of the antioxidation coating, which limits the maximum operation tem perature, was studied with the help of the same experimental technique s. A 500-kW induction plasma generator was used for testing large diam eter disk samples, sufficient for making samples for after-testing mea surements of ultimate bending strength. Experiments showed that residu al ultimate bending strength of the material was essentially without c hange after 1, 3, 10, 20, and 30 reentries simulation testing. This wo rk was carried out in the Plasma-Materials Interaction Laboratory of t he Institute for Problems in Mechanics of the Russian Academy of Scien ces.