Autovole processes in deprivation plasma coatings

Abstract

Autowave processes that arise when depositing plasma coatings are considered. Composite cathodes and stainless steel cathodes were used for the production of coatings. Microhardness measurements were made along and across the sample in an amount up to 50 pieces. Microhardness plots are periodic structures with a wavelength of the order of 10^–4 m. The diffusion coefficient is of the order of 10^–8 m²/s, i.e. we have a system with small diffusion. The deposition of coatings in a plasma is a thermodynamically nonequilibrium process in an open system. The nonlinearity of the equations arises from the motion of the interface and the small diffusion of surface atoms. In this case, an autowave process arises. The experimental and theoretical results obtained by us fit into the model of macroscopic localization of plastic flow. In this model it is shown that the localization of plastic flow in metals and alloys has a pronounced wave character. The theory of crystallization of a cylinder of finite dimensions developed by us relates to problems with a moving interface and is called the Stefan problem. From a mathematical point of view, boundary-value problems of this type are fundamentally different from the classical problems of heat conduction or diffusion. Due to the dependence of the size of the flow transfer region on time, classical methods of separating variables and integral Fourier transforms are not applicable to this type of problems, since, remaining within the framework of classical methods of mathematical physics, it is not possible to coordinate the solution of the equation with the motion of the phase boundary boundary. The motion of the boundary of the phase difference leads to a nonlinearity of the system of equations, which leads to the appearance of autowaves.