Control of the nitrogen content in nanocomposite TiN/SiNx coatings deposited by an arc-sputter hybrid process

We have developed a reactive hybrid process for the deposition of TiN/SiNx composite layers where titanium is eroded from a conventional, industrial arc source and silicon is simultaneously sputtered from a magnetron target in argon/nitrogen atmosphere. The Si/N ratio of the SiNx phase in the film is related to the nitridation state of the silicon target which in turn is controlled by the Ar/N2 mixture. Monitoring the characteristics of the silicon target allows an effective control of the process. Nanocomposite TiN/SiNx coatings show enhanced protective properties compared to coatings of pure TiN because the addition of silicon results in an improved oxidation resistance. The improvement depends on the stoichiometry of the SiNx phase which controls the crosslinking in the matrix and to the TiN grains. In composites with insufficient nitridation of the SiNx phase no improvement of the hardness is observed.