Deep-drawing of aluminum sheets without lubricant by use of diamond-like carbon coated dies

In this article we propose the use of a diamond-like carbon (DLC) film coated onto the die in order to deep-draw aluminum sheets without lubricant. The use of a DLC coating has, surprisingly, been found to eliminate the need for any lubricant to prevent adhesion of aluminum to the die material during up to about 6200 deep-drawing operations in which square cups, each with a size of 20 x 20 x 12 (depth) mm, were produced. The DLC was coated onto a WC-Co alloy drawing die by means of an ion plating apparatus in which a tri-electrode-type DC are discharge ion source with a hot filament, an anode and a reflector were used with a precursor of benzene. The work material was 1 mm thick A5000 aluminum sheet. In contrast to the DLC-coated die, an uncoated WC-Co alloy deep-drawing die operated without any lubricant caused fracture of the aluminum sheet after only five repetitions of deep-drawing because of the strong adhesion of the material to the die. This demonstrates the dramatic effects of the DLC coating.