Ti/TiN multilayer coatings: deposition technique, characterization and mechanical properties

Ti/TiN multilayer coatings with multilayer periods in the range 5-50 nm and a final thickness of 2 mum were deposited on steel substrates by cyclic mo dulation of nitrogen gas flow into the chamber of a PVD sputtering device. Coating characterization was performed by cross-sectional transmission elec tron microscopy, glancing-angle X-ray diffraction and instrumental indentat ion testing. Individual alpha -titanium and titanium nitride layers were al ways observed, although for the finer microstructures, the TiN layers were thicker than the Ti layers by a factor three. The plastic hardness of the f ilms increased steadily with decreasing layer spacing, following a Hall-Pet ch relationship. Finally, a hardness value of 42 GPa was reached, which is similar to that of a thick TiN monolayer, prepared under the same coating c onditions. (C) 2001 Elsevier Science B.V. All rights reserved.