IMPROVEMENT OF CARBON-BASED COATINGS FOR USE IS THE COLD FORMING OF NONFERROUS METALS

In order to avoid the consumption of lubricating agents and thereby re ducing their impact on the environment in the cold working of non-ferr ous metals such as aluminium and titanium, the outstanding tribologica l properties of diamond-like carbon and its variations are of great in terest. A big problem of the application of the coatings is their usua lly insufficient adhesion to steels used in the cold working industry. In this paper we report on new results on carbon-based coatings such as amorphous hydrogenated carbon (a-C:H) and metal-containing a-C:H wi th respect to cold forming conditions. The hardness of the films as me asured with a nanoindentation system, adhesion as tested with a Rockwe ll and a scratch test and frictional properties as tested in a pin-on- disk test with respect to aluminium and titanium counterbodies are des cribed. By incorporation of metallic interlayers, the adhesion to the substrate could be largely improved. Adhesion and friction of the nonm etallic counterbodies could be minimized, although it is still not sat isfactory in certain contact situations. However, use of carbon-based films in the cold forming of non-ferrous metals seems to be practical.