Effects of heat treatment on mechanical properties of ceramic thin films

In our previous studies, we found that heat treatment after coating with TiN could be an effective method to improve the mechanical properties of TiN-coated steel. However, it was not clear whether a similar effect could be obtained for other types of ceramic thin films. The heating temperature condition suitable for improvements of various thin films also has not yet been revealed. In this study, for three kinds of ceramic thin films, TiN, TiAlN and CrN, deposited on steel substrates by an arc ion plating method, heat treatment was carried out at various temperatures ranging from 733 to 1333 K, and the effects of heat treatment and heating temperature on mechanical properties of these films were investigated. For all films, the adhesive strength was improved effectively by heat treatment. This improvement could be explained by the formation of a diffusion layer between the film and the substrate in the heat treatment process. Wear resistance was also improved by heat treatment in all the films, though hardness decreased. It was also found that the friction coefficient in each film was decreased by the heat treatment, and this decrease in friction coefficient could be one reason why wear resistance was improved.