Friction reduction in dry forming by using tetrahedral amorphous carbon coatings and laser micro-structuring

Friction has a dominant influence on manufacturing processes. In deep drawing of sheet metals, lubricants are regularly used to reduce friction forces. However, significant production costs originate from their supply, application, removal and disposal. The negative environmental consequences of using lubricants promote extended research on lubricant free deep drawing processes and tools. A combination of macro-structuring in the flange area and micro-structuring of ta-C layers at the pulling edge radius of deep drawing tools is identified to compensate the loss of tribological functions. Surface texturing of semi-finished sheet metals also supports friction reduction by minimizing the contact area to the deep drawing tool. In this study, a variation of ta-C coating iterations with several coating and decoating steps, as well as microstructuring of the ta-C coatings using Direct Laser Interference Patterning was used on cylinders in draw bend test rigs. The resulting friction coefficients between the cylinders and steel stripes show minimal friction for ta-C covered draw bend tools.