High-Velocity Gas-Flame Spraying by Two-Chamber Torch Devices

Abstract

We examine a new method for high-velocity gas-flame spraying: spraying of powdered materials by two-chamber torch devices, implementing the concept of flow rate control of the parameters of the carrier gas stream in their gasdynamic circuits. We give the parameters for the two-phase stream in the circuit of a two-chamber torch, obtained as a result of numerical modeling of the thermodynamic and gasdynamic processes in it. We show that maximum thermal efficiency for such torches is achieved when the flow rate of the gas phase through the front combustion chamber makes up 10 to 50% of the total flow rate. In this case, the enthalpy of the particles achieved during heating in two-chamber torches is 1.5 to 2 times greater than the enthalpy in torches of conventional design. The results of a comprehensive structural analysis of the coatings deposited by the new type of torches are evidence that they are of good quality and have high-level service properties. We demonstrate the prospects for using a composite powder based on Al₂O₃ – SiC for spraying low-porosity wear and corrosion resistant coatings that are functional at elevated temperatures.