The significance of carbon on the microstructure of TiAlN–C coatings deposited by reactive magnetron sputtering

A series of TiAlCN coatings with different carbon contents have been deposited by a reactive sputtering of TiAl target under an environment with a mixture of Ar, N2 and CH4 gases. Microstructural changes, starting from pure TiAlN and then into TiAlCN with the increase of the carbon content, have been clearly demonstrated. This occurrence is due to the carbon atom substitution that results in a small alternation of the interplannar lattice parameter. The coating initially shows a strong preferred (1 1 1) texture in the pure TiAlN but becomes more randomly oriented at the higher carbon contents. Evidence was found for the presence of a free carbon phase, which provides the possibility to accomplish the self-lubricant coating.