Improvements in the Microstructure and Wear Resistance of Cast-Iron Coating Plasma-Sprayed with Mo-Partially Cladded Cast Iron Powder

Limited inter-splat bonding is a key problem in thermally sprayed coatings. The use of impinging particles with a high temperature is a crucial factor for obtaining superior bonding between splats. In this work, an attempt was made to raise the temperature of plasma-sprayed cast iron particles by using Mo-cladded gray cast iron (GCI) powder as the feedstock. The cladded powder was prepared by a ball-milling process. Heat transfer between the powder particles and plasma jet was numerically simulated by a finite element method. Cast iron coatings were prepared by atmospheric plasma spraying using both GCI and Mo-cladded GCI powders. The microstructure and wear resistance of both coatings were comparatively investigated. After ball-milling, the GCI powder was partially cladded by Mo, with a surface cladding ratio of 77.2%. The experimental results showed that Mo cladding inhibited particle oxidation by forming volatile molybdenum oxide. The simulated results showed that Mo cladding elevated the surface temperature of the impinging cast iron particles by 415 K. Consequently, the inter-splat bonding within the coating and wear resistance was significantly improved.