In Situ Particle Behavior of Cast Iron Powder by Suspension Plasma Spraying

An important issue for atmospheric plasma sprayed metal coatings is the oxidation involved during processing that significantly affects its phase composition and microstructure and thus the overall coating properties. In this study, suspension thermal spraying was used to manufacture cast iron coatings with high amounts of graphite carbon as solid-lubricant, because graphite structure is considerably diminished in molten droplets of the spray material due to the dissolution into molten iron and/or the oxidation. Additional graphite formation based on the soot reaction of liquid hydrocarbon was observed. Oxidation strongly affects the soot reaction during suspension thermal spraying. Therefore, setting-up of a shroud around the plasma plume is quite effective to prevent the oxidation of hydrocarbon.