New Possibilities of Plasma Spraying of Wear-Resistant Coatings

摘要

A plasma method for obtaining wear-resistant coatings is proposed that enables one to spray powders of different dispersions and composition, as well as to obtain coatings of low porosity and increased hardness. A ceramic or metal powder enters in the jet of thermal plasma where the particles are uniformly heated due to a new design of a plasmatron with an interelectrode insert and coaxial injection of powder into a plasma jet. In this case, a high efficiency of plasma spraying and the control of layer structure and quality are ensured. Thermal and technological studies of the efficiency of the formation of a high-temperature heterogeneous jet and the plasma spraying of coatings of metallic (a fraction of 40-100 μm) and aluminum oxide powders with basic main particle size of 28-40 μm were conducted using an annular input of powder with gas focusing. The nature of flowing Al_2O_3 particles from the radial-annular slot for powder input with transporting gas is investigated. Statistical distributions of temperature and velocity of the particles on the axis of the plasma jet are presented. The sizes of the area of plasma jet are determined in which particles are melted as much as possible. The results of spraying and study of the coating properties are given.