Micro deep drawing of micro cups by using DLC film coated blank holders and dies

Lubrication is one of the key problems in metal forming, and this is even more important in micro forming because of size effect on friction. Diamond like carbon (DLC) film coated blank holders and dies were used in forming micro cups with drawing blank diameters of 2 mm. A plasma immersion ion implantation and deposition (PIIID) process was proposed to treat the blank holders and drawing dies. Raman spectrum, scratch test, and ball-on-disc test were used to investigate the structure, adhesion strength, and tribological property of the DLC films. The micro deep drawing experiments were carried out at room temperature on a universal testing machine at a drawing velocity of 0.1 mm/s without lubrication, and under the lubrication of castor oil and DLC film. The results showed that the micro cups were well formed with a minimum inner diameter of 0.95 mm under the lubrication of DLC film. The DLC film which dramatically decreased the drawing force and increased the limit drawing ratio (LDR) was better than other lubrication conditions and can be chosen as a proper lubricant in micro forming for mass production.

Research Highlights
► A plasma immersion ion implantation and deposition process was proposed to treat the blank holders and drawing dies.
► Micro deep drawing experiments were carried out without lubrication, and under the lubrication of castor oil and DLC film.
► Micro cups were well formed with a minimum inner diameter of 0.95 mm under the lubrication of DLC film.