Numerical anal of O-2 concn. field in the stream of low-temp. plasma and the protective layer stream of N-2, was carried out. The plasma spraying was used for prodn. of ceramic coatings on machine parts. The N-2, stream was used for protecting ceramic powder prior to oxidn. Phys. and math. models of fixed 2-dimensional diffusion with forced convection were developed on axially symmetric 2-dimensional velocity field of plasma jets.