The CVD alumina coatings were deposited on carbide cutting tools using gas mixtures of H-2, CO2 and AlCl3 at the temperatures between 960-1000 degrees C, one atmosphere pressure and for different gas flows of H-2, CO2. The AlCl3 gas is produced in a generator by passing the HCl gas through the mechanically worked aluminium granules. In a simulated laboratory setup it was found that the reactivity of aluminium granules with HCl was increased drastically. Thickness measurements showed that by using worked granules, the alumina thickness for the same conditions increases from 0.75 to 3 mu m. Moreover, it was found that with increasing the coating temperature and flow of gases, deposition rate was increased. Calculations showed that the process is far from the equilibrium condition. It was found that the reaction is kinetically mass transfer controlled in the boundary layer. The activation energy of the process was equal to 207.02 Kj/mol.

Keywords: CVD; Aluminium granules; Mechanical working; Activation energy