Suppression of pick-up defects in hot extrusion of 6063 aluminum alloy by using PVD coating die

Abstract

6000 series aluminum alloys are used in a variety of fields including architectural products and automobiles. These products require complex cross-sectional shapes and high productivity. In the forming of products that meet these market requirements, surface defects such as pick-up and tearing occur. In the previous report, we focused on the mechanism of pick-up defects on the extrusion surface. The cause of the pick-up defects was the preferential adhe-sion of Mg and O to the die bearing surface. In this paper, a die coating is applied as a method to suppress the pick-up defects. AlCrN, TiAlN, Diamond-like carbon (DLC) were applied and compared to the Nitriding. The number of pick-up in the DLC increased as the stroke progressed, and surface layer delamination of DLC was observed after extrusion. Mg oxide wasn't observed in AlCrN and TiAlN on the bearing surface. And, surface delamination wasn't observed with these coatings. The coatings such as AlCrN and TiAlN to the die bearing surface were effective in suppressing pick-up defects.