Investigation of plasma jet gas-dynamic effect on a substrate in conditions of diamond coating synthesis

Experimentally, it was shown that using a gas-dynamic correction in the plasma torch operation mode of jet expansion absence increases the efficiency of DC synthesis more than 10 times. Moreover, the diameter of the homogeneous part of a coating is increased not less than twice in relation to the diameter of the plasma jet. The theoretical explanation of the obtained result is given. It was shown that at subsonic speed of plasma flow spreading along the substrate radius, this effect can only be obtained at Reynolds numbers not exceeding the critical value R-r less than or equal to R-r cr = 13456. The maximum area of uniform thickness DC is not less than 6 cm(2). (C) 1999 Published by Elsevier Science S.A. All rights reserved.