Simultaneous oxidation and decarburization of cast iron powder during plasma spraying

Plasma spraying of cast iron powder (grit) containing 2.64% C was investigated. A water-stabilized plasma torch was employed in spraying. Some characteristics of molten particles flying in the plasma stream were measured at various distances from the powder injector, in particular average surface temperature and average velocity. Oxidation and decarburization accompanying the flight of molten cast iron particles in the plasma stream were studied by determining the oxygen and carbon concentrations before and after the in-flight spraying period. At the latter moment, the reactions were stopped by trapping the particles in liquid nitrogen. Significant effects of the powder feed rate and the feeding distance on oxidation and decarburization were observed. X-ray diffraction and Mossbauer spectroscopy yielded some information on the structure changes of cast iron particles during the in-flight period of plasma spraying.