Plasma sprayed ferrite-based infrared radiation coating directly from transition metal oxides without high-temperature roasting

Ferrite-based infrared radiation coatings with high emissivity were obtained by plasma spraying on carbon steel substrate directly from the mixtures of Fe2O3, MnO2, Co2O3 and NiO powders without high-temperature roasting. It was investigated whether high-temperature roasting process for raw powders before spraying could affect the phase, microstructure and infrared emissivity of coatings. It was revealed that the ferrites with spinel structure could be synthesized directly during plasma spraying process without previous high-temperature roasting. The phases and microstructures of coatings prepared from raw powders and high-temperature roasted powders were similar, and the coating from high-temperature roasted powders presented a similar emissivity (0.76-0.88) to that from raw powders (0.73-0.85). The high-temperature roasting process can be omitted when ferrite-based infrared radiation coatings are prepared by plasma spraying, which can simplify the process, save energy and reduce costs.