Diamondlike Carbon-Coated Dies for Deep Drawing of Aluminum Sheets

Soft and hard diamondlike carbon die coatings were used to deep draw aluminum sheets with a very light and environment-friendly water-soluble oil lubricant and even without a lubricant. The water-soluble oil lubricant with poor lubrication ability caused premature rupture of the aluminum blank when drawn with a noncoated steel die, whereas a die coated with soft diamondlike carbon (WC/C) had a lifetime of over 7000 drawing operations. A cost-effective die could be made of a die steel body on which a sintered tungsten carbide alloy overlayer was deposited by high-velocity thermal spraying and further coated with a hard diamondlike carbon (DLC), which gave a life of up to 6000 operations even without a lubricant. Tool life was almost equal to that for a solid sintered carbide alloy die coated with DLC.