Improvement of carbon-based coatings for use in the cold forming of non-ferrous metals
In order to avoid the consumption of lubricating agents and thereby reducing their impact on the environment in the cold working of non-ferrous metals like aluminium and titanium, the outstanding tribolocical properties of diamond-like carbon and its variations are of great interest. A big problem of the application of the coatings is their usually insufficient adhesion to steels used in the cold working industry. This paper reports on new results on carbon-based coatings like amorphous hydrogenated carbon (a-C:H) and metal containing a-C:H (Me-C:H) with respect to cold forming conditions. The hardness of the films as measured with a nanoindentation system, adhesion as tested with a Rockwell and a scratch test and frictional properties as tested in a pin-on-disk test with respect to aluminium and titanium counterbodies are described. By incorporation of metallic interlayers, the adhesion to the substrate could be largely improved. Adhesion and friction of the non-metallic counterbodies could be minimised, thou-h it is still not satisfactory in certain contact situations. But use of carbon-based films in the cold forming of non-ferrous metals seems to be practical.