Development and tribological characterisation of magnetron sputtered TiB2 and Cr/CrN coatings

The aim of this thesis was to develop wear resistant physical vapour deposited coatings of TiB2 as well as multilayers of Cr/CrN. The correlation between deposition parameters and fundamental coating properties such as microstructure, composition, residual stress and hardness has been investigated. Finally, the influence of these properties on the coating behaviour in tribological applications has been evaluated. It is shown that the use of electron bombardment of the growing coating during d.c. magnetron sputtering is beneficial for the growth of superhard TiB2 coatings. Furthermore, electron bombardment results in TiB2 coatings with significantly lower residual stresses than coatings deposited using ion bombardment. The low stresses in these coatings open up the possibility to deposit thicker PVD coatings, as confirmed in this thesis. In addition, the use of TiB2 coatings in tribological contacts against aluminium proved to be superior to many other commercial coatings used today, with respect to wear resistance, anti galling properties and a low friction. Finally, a model is proposed which explains the observation that the abrasive wear resistance of multilayered Cr/CrN coatings can outperform that of the individual constituents. The model was found to satisfactory predict experimental data