ta-C coated tools for dry forming of aluminum sheets

The suitability of ta-C coated tool surfaces for sheet forming of aluminum alloys was examined by strip-draw testing. It was shown that ta-C coatings, which are known as DLC coatings with superior wear resistance are also favourable concerning the anti-adhesive behaviour. In attempts with AlMg5Mn- as well as Al99Mg1-sheet materials several hundred sheets could be formed without noticeable aluminum adhering at the ta-C coated tool surface. Neither the coefficients of friction nor the surface qualities of the aluminum sheets worsened during the observed period. Compared with tests of uncoated tools in combination with lubricants, the dry ta-C coated tool behaves comparable with a good lubricant. In a real clinch test with aluminum sheets the positive results from strip-draw experiments were confirmed. Using ta-C coated clinching stamps and no lubricants a large number of clinching processes could be performed without noticeable adhering and increase of stripping forces.