The preparation of composite powders for plasma spraying by the mechanofusion process and planetary-milling was studied. First, silicon carbide particles have been coated with an alumina shell by means of a mechanofusion (MF) process in order to avoid or at least limit their oxidation during their flight in a plasma jet. A nearly rounded shape of the final composite particles was induced by the mechanical energy input retaining the prismatic geometry of the SiC inner particles. It is proposed that the coating mechanism is governed by agglomeration and rolling phenomena. Second, the same SiC-A1(2)O(3) system was MF processed adding a SiC planetary-milled powder in order to control the finest particles agglomeration. Three types of composite particles were found: (i) a raw SiC particle coated by A1(2)O(3), (ii) milled SiC particles embedded in an A1(2)O(3) agglomerate and (iii) a mixture of raw and milled SiC particles embedded in an A1(2)O(3) agglomerate suggesting that the final composite size can be controlled by using a SiC milled powder as an agglomeration control agent.