MECHANISM OF SHS REACTIVE FLAME SPRAYING Al₂O₃-BASED MULTIPHASE COATING

The Al₂O₃-Al₂Cu₃ multiphase coating was produced on an iron substrate by means of SHS reactive flame spraying with Al and CuO as main reactants ignited by the oxyacetylene flame. The morphology of the particles that were quenched and gathered up at different flying distances was observed.The constituent and microstructure of the coating were analyzed.The essential procedure of SHS spraying was summarized with regard to the special conditions of SHS chemical energy between Al and CuO and the physical and geometrical features of aggregated particles. It is concluded that the aggregated particles, acting as solo reactive units respectively, form into coating after going through four successive stages——pregnant reaction, flight combustion, collision, structure transformation and solidification. On the basis of this essential procedure, the reactive mechanism, structure transformation, solidifying behavior, microstructure and dominant factors in each stage were discussed in detail.