Fe2O3-Al composite powders were deposited onto steel substrate by plasma spraying. The reaction products of the Fe2O3-Al composite powders in the plasma flame and their solidification process were investigated. The results showed that the reaction products of the Fe2O3-Al composite powders in the plasma flame were Fe-Al-O ceramic melt and Fe melt. Fe was not always formed in the reaction products of each composite particle, and the formation of Fe was dependent on the composition distribution and the reaction kinetics process of each composite particle. The composition inhomogeneity, discontinuity and porousness of the composite particles resulted in the difference of the reaction kinetics of each composite particle and the composition difference of the droplets. Hercynite solid solution, Fe, Al2O3 and FeAl phases were formed by non-equilibrium solidification of the Fe-Al-O ceramic melt. For the smaller size droplet, when it spread on the substrate, the spreading droplet was quickly chilled to form equiaxed grains with size of 100-200 nm. Nano-sized or submicron equiaxed grains, nano-sized columnar grains and cellular structure were formed in the larger spreading droplet. Fe rich hercynite solid solution nucleated and grew preferentially and then Al rich hercynite solid solution grew, which form composition segregation in the columnar grains. The main phases in the composite coating were hercynite solid solution. (C) 2012 Elsevier B.V. All rights reserved.