WEAR MECHANISMS OF DIAMOND-LIKE CARBON COATED TOOLS IN TAPPING OF AA6351 T6 ALUMINIUM ALLOY

Abstract

The AA6351 T6 is an Al-Si-Mg alloy, widely used and easily accessible on the market, with low silicon content, sufficient to form magnesium silicates. The present work aims at analyzing the wear mechanisms acting over High-Speed Steels – HSS-E, Diamond-Like Carbon – DLC coated tools during the tapping operation of AA6351 T6 aluminum alloy. It was used a thread cutting tap with four helical flutes, diameter ϕ = 12 mm, and 1.5 mm thread pitch (M 12 x 1.5). Dry ambient was adopted to focus on the DLC performance. Ninety-six threads were machined using one single tool, and wear analysis was performed between the first and last threads. The main results showed aluminum adhesiveness, plastic deformations with more accentuated flank wear in the entry threads of the cutting tap, in addition to the detachment of the DLC coating. On the threads produced, several material detachments marks (adhered to the tool) were observed, as well as groove marks. These findings may help users in selecting appropriate cutting conditions as well as cutting atmospheres that can mitigate the tool wear.