AVS 46th International Symposium
    Thin Films Division Monday Sessions
       Session TF+VM-MoM

Invited Paper TF+VM-MoM1
Advances in Hard and Superhard Coatings for Tribological Applications

Monday, October 25, 1999, 8:20 am, Room 620

Session: Advances in Hard and Superhard Coatings I
Presenter: A. Matthews, University of Hull, UK
Authors: A. Matthews, University of Hull, UK
A. Leyland, University of Hull, UK
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Over the past twenty years there has been considerable progress both in the development of advanced coating processes and in the scientific understanding of tribological mechanisms. Typically these developments have occurred completely separately, to the extent that coatings researchers may seek to develop a new coating with a specific extreme property (such as high hardness) driven primarily by scientific curiosity, rather than a desire to fulfil an identified tribological need. Usually that need will (for example) require an enhanced range of properties (such as hardness, toughness and resistance to environmental degradation). Coatings researchers are now increasingly recognising this need and are fulfilling it through several exciting developments. These include multi-layered and nanocomposite coatings which combine high hardness (H) with a relatively low elastic modulus (E) (to provide increased toughness). These coatings thus minimise the E/H ratio - which is known to be a parameter which is closely related to wear resistance. Other developments involve so-called 'hybrid' or 'duplex' combinations of processes to fulfil specific tribological needs. We are now in sight of achieving functionally-graded coating structures which combine tough and stress-equalised bulk properties, together with the extreme hardness, thermal and chemical properties of the exterior. The paper discusses the developments which have been necessary to achieve this - such as optimisation of compound compositions in the case of nanostructured composites based on nitride, carbide and boride phases. Also in the case of hard oxide ceramics, mention is made of growth modelling studies and plasma process developments to achieve the desired phases.