Abstract
Thermal spray coatings of surfaces with metal, alloy and ceramic materials for protection against corrosion, erosion and wear is an intense field of research. The technique involves injection of the powder into a plasma flame, melting, acceleration of the powder particles, impact and bonding with the substrate. Feedstock powders of thermal spray applications have to meet several requirements. Particle shape, size and its distribution, powder flow characteristics and density are the important factors to be considered in order to ensure high spray efficiency and better coating properties. For smooth and uniform feeding of powders into the plasma jet, the powder particles have to be spherical in shape. In the present investigation powder particles are fed into the thermal plasma and spheroidized. The plasma was generated in a dc atmospheric plasma spray torch operating in non-transferred mode. Plasma processed powders were allowed to cool in atmospheric air inside a plasma reactor. The particle while free fall and cooling got spheroidized by surface tension forces. The feedstock powders were in the size range from 40 to 100 microns. The processed powders were analyzed through XRD, SEM/ Optical microscopy and irregularity parameter (IP) and roundness factor were determined. The same parameters were determined through theoretical methods and compared with experimental results.
