THE NANO-SCRATCH TESTER (NST) AS A NEW TOOL FOR ASSESSING THE STRENGTH OF ULTRATHIN HARD COATINGS AND THE MAR RESISTANCE OF POLYMER-FILMS

At present, functional coatings are used in increasingly demanding app lications that require good adhesion and specific resistance to damage . This has prompted a rising interest in improving the mechanical prop erties of polymer coatings, especially their scratch and mar resistanc e, as well as ultra-thin hard coatings as used for protective overcoat s in the magnetic storage industry. The nano-scratch tester (NST) is a new instrument overcoming the limitations of both the classical stylu s scratch test (normal force range) and the atomic force microscope te chnique (short sliding distances), allowing scratch lengths of up to 1 0 mm. Tangential force and penetration depth are simultaneously measur ed during the scratching process, both in a multipass contact fatigue mode. For high resolution inspection of the deformed or damaged area, a scanning force microscope (SFM) is integrated into the system. Exper imental results are presented for two very different types of material ; polymeric clear-font samples which give a range of mar resistance an d DLC ultra-thin films used as protective overcoats for hard disks. Th e results indicate very good reproducibility and confirm the applicati on of this new instrument for the accurate characterization of elastic ity, hardness, adhesion and mechanical integrity in coated systems whe re the film thickness is less than 1 mu m (C) 1998 Elsevier Science S. A. All rights reserved.