IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Engineering Monday Sessions
       Session SE-MoA

Invited Paper SE-MoA5
Structural and Chemical Interplays in Hard Coatings Properties: Multinary Transition Metal Nitrides

Monday, October 29, 2001, 3:20 pm, Room 132

Session: Surface Engineering I: Graded, Multicomponent, and Complex Coatings
Presenter: F. Lévy, Swiss Federal Institute of Technology in Lausanne - EPFL
Authors: F. Lévy, Swiss Federal Institute of Technology in Lausanne - EPFL
P. Hones, Swiss Federal Institute of Technology in Lausanne - EPFL
P.E. Schmid, Swiss Federal Institute of Technology in Lausanne - EPFL
R. Sanjinés, Swiss Federal Institute of Technology in Lausanne - EPFL
M. Diserens, Swiss Federal Institute of Technology in Lausanne - EPFL
Correspondent: Click to Email
Transition metal nitrides are useful as hard, resistant and protective coatings. Both film composition and film morphology have an influence on the functional properties like hardness, wear and corrosion resistance or colour. Physical vapour deposition techniques are flexible enough to allow a control of the chemical and structural characteristics. In turn, targeted or new coating properties can be obtained. In particular new coating chemistries can be explored by reactive sputtering, which is a clean, polyvalent process, compatible with elemental metal sources. Property improvements may be driven by structural and morphological features, as discussed for example in (CrMo)N ternary sputtered thin films. In contrast, the effects of electronic structure and chemical bonding are illustrated in (CrW)N. In single-phase refractory thin films, the hardness often increases with increasing substrate temperature T@sub s@. This effect has been related to an increase of the grain size d (e.g. in TiN, H@sub m@ = 23...35 GPa with d = 300...600 nm for T@sub s@ = 200...650 @degree@C). In CrN@sub y@, however, the increase in hardness from 8 to 19 GPa observed with increasing substrate temperature T@sub s@ = 330...680 @degree@C was not related to the grain size in a straightforward manner. For this material the grain size was always of the order of 40 nm. The porosity of the film, however, was reduced by substrate heating as demonstrated by an increase of the density. In the ternary compounds, for example in Cr@sub 1-x@Mo@sub x@N@sub y@, the grain size increases significantly in comparison with the binary end compounds. This grain size increase is accompanied by a loss of hardness. The morphology of the films remains columnar and the apparently increasing porosity can be held responsible for the deterioration of the mechanical properties. The chemical composition is determining for most properties, even if often masked by the morphological features. Such effects are present in binary compounds (CrN@sub y@) and are amplified in ternary systems ((Cr,M)N@sub y@ with M = Mo, W).