SMALL PARTICLE PLASMA SPRAY APPARATUS, METHOD AND COATED ARTICLE

摘要

A method of coating a surface using a plasma arc torch (10) comprises directing a plasma plume externally from a discharge end (10a) of the plasma torch (1) toward the surface, positioning a powder injector (20) proximate the plasma plume to introduce ceramic oxide powder particles at a size less than 20 microns diameter into an outer mantle of the plasma plume so that the powder particles are confined in the outer mantle, directing first and second gas jets at the plasma plume downstream of the powder injector (20) position and on opposite sides of the plasma plume to enhance entrainment of the injected powder particles in the outer mantle, circulating the powder particles in the outer mantle of the plasma plume for a residence time to heat the powder particles to melt them without substantial vaporization, and depositing the melted powder on the surface as a dense coating having closed porosity.