[P1-75] Crystal Growth Molecular Dynamics Simulation of alpha-Al2O3 Cutting Tools for Realizing Their Best Tribological Properties
Aluminum oxide (Al2O3) as coating materials has been used for cutting tools. It is widely applied on machining metals, because Al2O3 films show the tribological properties of high hardness and heat resistance. The Chemical Vapor Deposition (CVD) coating process for Al2O3 film is a very effective way to get its excellent tribological properties. AlCl3/CO2/H2 gas system is used for the CVD process to obtain the Al2O3 coating. At the beginning step of the CVD process, the surface reactions affect the orientation of Al2O3 surface. However, the relationship between the surface reactions and Al2O3 orientation is difficult to be clarified by the experiments. In this study, we investigate the details of surface reactions on the alpha-Al2O3 (0001) and (11-20) surfaces using computational simulation methods at the molecular scale. The alpha-Al2O3 take place through the hydrolysis reactions of AlCl3 and H2O. In order to clarify the surface reaction mechanism on alpha-Al2O3 (0001) and (11-20), we calculate the AlCl3 molecule adsorption on these surfaces using the first principles calculation. GGA-PBE functional is employed. One AlCl3 molecule is placed on various sites atom of alpha-Al2O3 (0001) and (11-20), and the system is optimized. The highest adsorption energies are -107.63 and -60.87 kcal/mol, respectively. The result indicates that AlCl3 molecule easily adsorbed on the alpha-Al2O3 (0001) surface. After the optimization of the AlCl3 molecule, the 6-coordinated Al and 4-coordinated Al of the AlCl3 molecule are observed on the alpha-Al2O3 (0001) and (11-20) surfaces, respectively. It means that 6-coordinated Al shows the stable adsorption state. Furthermore, molecular dynamics simulation is performed to clarify the surface reaction dynamics on the alpha-Al2O3 (0001) and (11-20). The details will be discussed on our presentation.